The Carbon Bomb
Climate Change and the Fate of the Northern Boreal Forests
GREENPEACE INTERNATIONAL (GP)
This report was researched and written by Kevin Jardine and edited by Lyn Goldsworthy, Abbie Thomas and Michael Szarbo for Greenpeace International.
Greenpeace International would like to acknowledge the work and assistance of the many people who reviewed various drafts. We would especially like to thank Robert Stewart, Ole Hendrickson, David Price, Michael Apps and Tim Lynham from Forestry Canada. H.H. Shugart from the University of Virginia, G.M. MacDonald from McMaster University in Ontario and S. Nilsson from the International Institute for Applied Systems Analysis in Austria also provided helpful advice. The ecology sections are much stronger as a result.
Within Greenpeace, we would like to thank Patrick Anderson, Bill Barclay, Francesco Martone and Christoph Wiedmer from the Forests Campaign; Kalle Hesstvedt, Marcus Rand, Jeremy Leggett and Erwin Jackson from the Climate Campaign; Bob Lyons and Donna Greenley from Greenbase; and Andrea Imada from Greenpeace Canada.
Designed by Wendy Farley. Produced by Social Change Media, Sydney, Australia and Lyn Goldsworthy.
Printed by MPH Graphics Inc Ontario, Canada
Published in 1994 by Stichting Greenpeace Council, Keizersgracht 176, DW1016, Amsterdam, The Netherlands.
A dragon of fire,
running wild through the forest,
Setting every tree ablaze and touching
off bright torches.
Like a monster starved for a century,
Like a rocket, the fire raced
Giving vent to rage - rage pent up for
thousands of years.
"An Ode to the Heroes of the Fire-Fighting" In a collection published by the Popular Art Centre of the Hinggan prefecture, Jiagedaqi, China.
THE NORTHERN BOREAL FORESTS make up almost a third of the Earth's forests, covering about 15 million square kilometres, and ranging across Russia, Canada, the United States, Scandinavia, and parts of the Korean Peninsula, China, Mongolia and Japan.
Drawing on the latest research on forest ecology, the impacts of recent climate change, and studies on projected future climate change, this report shows that between 50 and 90 percent of the existing boreal forests are likely to disappear as a result of a doubling of atmospheric levels of carbon dioxide and other greenhouse gases. This doubling is expected to take place over the next 30-50 years, and is likely to create abrupt changes in the Earth's climate that would result in severe forest decline. The rate of decline is still uncertain, but is likely to be rapid in many regions, and driven by massive fires, insect outbreaks and storms.
There is growing and alarming evidence that this decline is already beginning and is driven by a level of greenhouse gases in the Earth's atmosphere that is currently higher than has been seen in over 150,000 years.
The projected decline could contribute to the rapid release of hundreds of billions of tonnes of additional carbon dioxide into the atmosphere, accelerating the rate of climate change.
The emerging and potential impacts of climate change threaten the more than one million indigenous people who live in the boreal forest, as well as a loss of wildlife and plant diversity through the destruction of habitat. Key endangered species living in the boreal forest, such as the Siberian tiger, are already on the brink of extinction. Climate change and current logging practices further threaten such species.
Current logging practices are aggravating forest decline by decreasing the ability of the boreal forest to withstand disturbances, increasing stress by changing moisture and temperature regimes, and releasing greenhouse gases.
Serious disturbance of the boreal forest ecosystem can be traced back to an abrupt shift in the global climate in 1976. Since then higher temperatures have sparked larger and more frequent fires throughout the boreal forest, and the number of storms and damaging insect outbreaks has increased. These disturbances have been accompanied by a decline in conifer populations in the southern part of the boreal forest.
Unless atmospheric concentrations of greenhouse gases are quickly stabilized climate-vegetation models predict that large areas of boreal forest will be reduced to patchy open woodland and grassland, resulting in lowered biological diversity and a reduced ability to store carbon.
Studies of the global carbon cycle suggest that boreal forests are not absorbing as much carbon as they did before 1976. As a result, the atmosphere already appears to contain 10-15 billion tonnes of carbon more than it would have if forests had continued to absorb carbon at the pre-1976 rate.
If boreal forests continue to decline, estimates suggest that burning and rotting of boreal forests could contribute to the release of up to 225 billion tonnes of extra carbon into the atmosphere, increasing current levels by a third. This would accelerate the rate of climate change.
While it is possible that the boreal forest could expand into the frozen tundra as temperatures increase, such an expansion would likely be delayed by slow tree migration rates and the adverse effects of increased ultraviolet radiation on trees from ozone depletion.
Even in the long term, the boreal forest is not expected to expand enough to compensate for the deterioration in the southern part of the forest.
This report calls on policy and decision makers to radically rethink and change energy policies and logging practices in boreal forest countries in order to protect and preserve the climate and biodiversity. Such changes are consistent with their obligations under the Climate Convention and Biodiversity Treaty established by the 1992 UN Earth Summit in Rio de Janeiro, Brazil.
GREENPEACE BELIEVES that climate change and severe forest decline can only be halted by:
* A planned and orderly global phase-out of fossil fuels and their replacement by the efficient use of renewable and clean energy sources, including the immediate reduction of greenhouse gas levels by at least 20 percent by 2005.
* An end to global deforestation and the introduction of a programme of ecologically-based reforestation.
* The immediate phase-out of CFCs, HCFCs and HFCs, and their replacement by chemicals which do not damage the ozone layer or contribute to the human-induced greenhouse effect.
Rigging the Bomb: The Carbon Crisis
The Greenhouse Effect
FOR MILLIONS OF YEARS, the naturally-occurring greenhouse effect has played a crucial role in determining the Earth's climate. Greenhouse gases such as carbon dioxide and methane have trapped the Sun's heat near the Earth's surface, helping to evaporate surface water into clouds which later return the water to Earth.
Without the greenhouse effect, the Earth's average temperature would be 18 degrees Celsius below zero. The Earth would be a lifeless frozen wasteland. Instead, the greenhouse effect raises the Earth's average temperature by a full 33 degrees Celsius.
Rain and the sun' s warmth trapped by the greenhouse effect allow plants to grow and soils to form, and sustain the diversity of life. Plants and soils absorb carbon dioxide and other greenhouse gases from the air. For millions of years, a complex mixture of biological and hydrological systems released just enough carbon dioxide to maintain a fairly stable balance of these gases in the air.
IN A MONITORING STATION at the Mauna Loa volcano in Hawaii, scientist Charles David Keeling has been patiently measuring atmospheric levels of carbon dioxide since 1957. The results of his research, which have been confirmed and extended by scientists around the world, have profound implications.
Keeling discovered an enormous disruption in the global carbon cycle. His measurements showed that carbon dioxide levels were rising rapidly. Subsequent research has shown that the levels of most greenhouse gases have risen dramatically since the last century. Carbon dioxide levels have increased by about 25 percent since 1850, methane levels by 100 percent, and nitrous oxide levels by 15 percent. Next to water vapour, carbon dioxide is the most plentiful and important greenhouse gas.
For at least 160,000 years before the start of the Industrial Revolution, atmospheric concentrations of carbon dioxide never exceeded 300 parts per million. In 1992, carbon dioxide levels reached 355 parts per million, meaning that some climate change is already inevitable. Some scientists fear this is already happening.
A recently released Greenpeace review of extreme weather events suggests that the world's climate is, indeed, being disrupted in a manner consistent with the increased level of greenhouse gases in the Earth's atmosphere.
In the absence of urgent action by the governments of the world, this level may rise even higher, to more than 600 parts per million in less than fifty years. At this concentration. the world faces a very real and dangerous risk of catastrophic climate change. The United Nations' Intergovernmental Panel on Climate Change (IPCC) is made up of the world' s leading climate scientists. Their 1990 and 1992 reports estimated that some of the possible effects of rapid global warming could include:
* large-scale disruption of forestry, agriculture and fisheries;
* extinction of many plant and animal species on land and in the oceans;
* changing rainfall patterns;
* loss of huge tracts of coastal land under rising seas as the oceans expand;
* less access to less reliable water supplies in many parts of the world;
* serious adverse effects on human health.
Writing about the impacts on forests, the IPCC said: "It is possible that many tree species will not be able to change their geographic distribution as fast as the projected shifts in suitable climate and extinctions may occur."
The reality could be even worse. The IPCC has warned that its calculations do not include climate "feedbacks" such as biomass reactions to a warming climate, which could have the effect of accelerating global warming. This could include the release of huge quantities of heat-trapping methane from tundra regions north of the boreal forest. Compared to the amounts of carbon dioxide and methane currently in the atmosphere, natural reservoirs of these gases trapped in Arctic tundra, permafrost, and the world's oceans, are huge.
In a warming world these gases could be released to the atmosphere, feeding into the warming process and increasing its impact. A runaway greenhouse effect is therefore a possibility. A significant minority of scientists think it a probability. This would result in rapidly accelerating and unstoppable increases in global temperatures, with serious climate change and ecological impacts.
"The rate of change
predicted by the IPCC
is 15-30 times faster
than any global
ever known before."
Fossil Fuels and Deforestation
HUMANS ARE ALMOST entirely responsible for this disruption of the global carbon cycle, mainly through burning fossil fuels which increase the level of carbon dioxide in the atmosphere, and removing forests which act as "carbon sinks" by absorbing carbon dioxide. Approximately 7.6 billion tonnes of carbon are currently released into the atmosphere each year. Six billion tonnes is from fossil fuels, and an estimated 1.6 billion from deforestation.
The burning of fossil fuels such as coal, oil and natural gas - themselves largely the remains of ancient forests - has expanded rapidly since the late 19th century. Carbon emissions from fossil fuels have increased around 4.3 percent each year since then, only declining when industrial production slowed during the Great Depression and the two World Wars.
Carbon dioxide is also released into the atmosphere when forests are cleared using fire in tropical countries such as Brazil and Indonesia, and as exposed forest soil decomposes. The agricultural crops which usually replace tropical forests have a far lower capacity to store carbon.
Significant amounts of carbon are also released by the logging of temperate and boreal forest, especially by the logging of old-growth temperate forest of the Pacific Northwest and British Columbia, but also by the rapidly increasing logging operations in the boreal forest.
Deforestation does more than release carbon to the atmosphere; it also reduces the ability of forests to store carbon and act as a carbon sink by destroying them.
Setting the Mechanism: Climate and Boreal Ecology
A Vast Natural Resource
THE NORTHERN BOREAL forest, also called the taiga, is a vast ecosystem that encircles the northern hemisphere and covers 1.5 billion hectares. or 11 percent of the Earth's land surface.
The forest ranges from Alaska in the far west, through most of Canada, across the Atlantic to Norway, Sweden and Finland, through vast areas of Russia, and into parts of China, Mongolia, the Korean Peninsula and northern Japan.
Small fragments also exist in mountainous areas south of the main forest. This mountain or alpine ecosystem is sometimes called "oroboreal", from the Greek word "oro", or mountain. Oroboreal forest is found throughout the Rocky Mountains and in alpine regions of Europe.
About 40 percent of the Earth's land surface is covered by dense forest, shrubland and wooded grassland. The northern boreal forest, the temperate forest of the mid-latitudes and the tropical forest that grows near the equator are the three great forest ecosystems.
Forests have three vital functions. They help to regulate the Earth's climate, are home for millions of indigenous people and most of the Earth's terrestrial animals and plants, and they are the basis of a major global industry.
Thermostat For The Planet
FORESTS AFFECT THE CLIMATE in several ways. They have a profound effect on the local, or microclimate. Trees provide shade which lowers summer temperatures and prevents soil from drying out. They reduce heat loss from the ground in winter, and provide shelter from wind, preventing storm damage that might otherwise occur in more exposed areas. By regulating the global carbon cycle, forests also have a profound effect on the global climate.
The carbon cycle is one of the major systems that drives the Earth's biosphere and climate, and is, in a sense, the way the Earth breathes. The complex interaction between the boreal forest and climate is best understood by tracing the path of carbon through the biosphere and atmosphere.
Forests influence the global climate by taking in carbon dioxide and releasing it back into the atmosphere. Trees extract carbon from the atmosphere through photosynthesis which is driven by sunlight. The carbon is combined with water and nutrients from the soil to create the materials trees need for survival. Trees and animals also release carbon dioxide back into the atmosphere through a process called respiration.
The carbon stored in trees is eventually returned to the atmosphere via decomposition. Trees drop debris onto the forest floor, and eventually die, becoming part of the litter and soil. bacteria and insects break down this organic material, releasing carbon back into the atmosphere in the form of carbon dioxide where it can be used again. Animals also consume the carbon extracted from the air in the form of plants and other animals, and so it makes its way through all life on the planet.
"The boreal forest
makes up a third of
the Earth's forests" 
A Treasure Chest of Carbon
A VAST AMOUNT OF CARBON is locked up in the world's forests. While the atmosphere currently contains about 750 billion tonnes in the form of carbon dioxide, forests contain about 2,000 billion tonnes of carbon. Roughly 500 billion tonnes is stored as trees and shrubs and 1,500 billion tonnes as peat bogs, soil and forest litter.
Each year about 5 percent of this amount, or 100 billion tonnes, is cycled through the atmosphere. This cycle is in rough balance, with about 100 billion tonnes absorbed through photosynthesis, 60 billion tonnes released by decomposition, and 40 billion released by respiration.
Until recently, the level of carbon dioxide in the atmosphere has remained almost constant for 6,000 years, suggesting a remarkable system of ecological checks and balances. Even a small change in photosynthesis, decomposition or respiration rates could, over a few decades, cause a major shift in carbon dioxide levels and global climate. And yet this has not happened.
HOW CLIMATE SHAPES THE BOREAL FOREST
BOREAL FORESTS, LIKE ALL forests, play an important role in regulating the world's climate. In return, climate has a profound effect on the forest.
Boreal forests are complex ecological communities supporting a wide diversity of people, animal and plant life, and habitats. More than one million indigenous people live in the boreal forest. Tribes including the Dene and Cree of Canada, the Sami or Lapplanders of Norway, Sweden and Finland, the Ainu of northern Japan, and the Nenets, Yakut, Udege and Altaisk of Siberia have lived in balance with the forest for thousands of years.
The boreal forest is probably as widely known for its wildlife and endangered species. Its beautiful native bird species are well known around the world and include hawks and owls; crows, ravens and jays; ptarmigan and grouse; woodpeckers and seed- eaters such as finches, chickadees, and crossbills.
Apart from the seed dispersing function they perform, birds also eat forest insects such as mosquitos and black flies, and control caterpillar and beetle populations capable of devastating tree stands. Insects such as the North American mountain pine bark beetle and Siberian silkworm can periodically explode and kill off trees over millions of hectares.
The boreal forest is also home to a rich diversity of native mammals ranging from moose, deer, beavers and wolverines, to porcupines, squirrels, lemmings, fishes and martens. Caribou or reindeer live in the northern part of the forest and the tundra beyond. The large predators of the forest include black and grizzly bears, wolves, cougar, and Iynx. The habitat of the highly endangered Siberian tiger includes the southern extent of the boreal forest in the Russian far east.
The Forest Climate
TO THE NORTH the boreal forest is bounded by the tundra, a mostly treeless expanse of shrubs, grass and lichen that stretches to the ice packs of the polar desert and the Arctic Ocean. At its southern edge are grassland and remnants of the surviving maple and oak temperate broadleaf forests.
For much of the year the forest is locked in a cold winter freeze down to minus 40 degrees Celsius during which boreal life almost comes to a halt. The short boreal summer brings long, warm periods of daylight that lead to rapid boreal growth. The northern parts of the forest are dominated by permafrost or permanently frozen soil. In these areas, summer warmth only melts a thin layer of soil, and in winter there are only very short periods of daylight.
MUCH OF THE FOREST consists of stands of evergreen conifers. In North America the forest changes from pine to spruce and then to fir from west to east. Scots pine and Norway spruce are common in Scandinavia, while the deciduous larch is dominant in much of Russia. Several less abundant broad-leaved deciduous species also live in the boreal forest, including aspen, poplar, birch, willow and alder.
A variety of shrubs and grasses grow beneath the forest canopy, and the forest floor is usually cloaked in a rich mantle of moss or lichen. Fallen leaves and twigs form a forest litter that decays over centuries to create a deep and long-lasting forest soil which contains more organic matter than the trees.
APPROXIMATELY 2.6 MILLION hectares - almost a fifth of the forest - is covered by deep layers of decomposing peat moss. These peatlands form an ecosystem as important as the tree stands. Covered by hundreds of thousands of shallow lakes and fens, peatlands are among the most ecologically important wetlands. During the short boreal summer, these wetlands are a breeding ground for many migratory ducks and geese.
THE CLIMATE MAINLY DETERMINES where boreal forest grows. In Canada, for example, the extent of the forest is determined by growing degree-days or the number of days each year above 5 degrees Celsius multiplied by the average daily temperature. This means that grassland or deciduous hardwood species replace boreal forest in southern areas with too many growing degree- days, while the forest is replaced by tundra in northern areas with too few growing degree-days. A similar correlation between climate and the boreal forest is found in Europe and Asia.
PAST PATTERNS SHOW THAT specific climatic conditions are necessary for healthy boreal forest growth. If conditions change, so does the forest. For example, the boreal forest responded rapidly and dramatically to the ending of the last ice age. At their fullest extent, some 18,000 years ago, huge ice sheets covered most of Canada, northern Europe, and western Siberia, reaching down into Ohio in North America and as far as northern Poland in Europe. The boreal forest was located much further south than today. Pockets survived in icy shelters on the peaks of mountains that rose above the ice sheets, and at the foot of glaciers in regions such as Kansas and Nebraska.
As the Earth warmed between 17,000 and 8,000 years ago, the boreal forest shifted northwards. In Kansas and Nebraska, as the climate became hotter and drier, the forest was replaced by grassland. In eastern Siberia, which was largely not covered by glaciers, the cool mixture of forest and tundra gave way to bands of vegetation, with boreal forest bounded to the south by temperate broad-leaved forest and grassland. The boreal forest also grew onto land left by retreating glaciers, and in some places reached the shores of the Arctic Ocean.
Can It Adapt?
PAST CHANGES IN the Earth's climate have caused profound changes in the location and extent of the boreal forest. These changes, though immense when measured over millennia, happened at a far slower rate than the climatic change expected over the next few decades. Can the forest adapt in time?
DISTURBANCE AND SUCCESSION
THE CLIMATE ALSO CONTROLS the location and distribution of tree species in the boreal forest by shaping the two opposing forces that drive boreal ecology: disturbance and succession. Disturbance by fire, insect and storm activity creates openings in the forest and occasionally removes tree stands over a large area. This natural process benefits the forest by preserving diversity, and removing ageing stands.
Once an opening is created, a second process called succession takes place, in which pioneer species such as grasses, herbs and shrubs move in. Depending on the local climate and terrain, these pioneer species may later be replaced by broad-leaved trees such as aspen and birch, and these may in return be replaced by spruce and fir. If left undisturbed for several centuries, coniferous boreal forest in cool lowlands can be replaced by peatlands through a process called paludification.
Boreal species form a natural spectrum ranging from grasses to spruce and fir to peatlands. Species on the right of the spectrum are long lived, slow growing, and tolerant of the deep shade found in old-growth coniferous forest. Species on the left are shorter lived, faster growing, and need more sunlight.
Disturbances that create sunlit openings in the forest often push the species in a boreal stand further to the left of the spectrum. In the absence of new disturbances, succession gradually moves the forest back to the right, towards a dense old-growth forest of spruce and fir.
The boreal processes of disturbance and succession may have played a significant role in exaggerating changes in the Earth's past climate. As the Earth approached an ice age, the frequency of disturbances was likely reduced throughout most of the boreal forest, and the forest tended towards peatlands and old-growth coniferous forests - the right side of the boreal spectrum. These ecosystems stored large amounts of carbon, reducing the level of carbon dioxide in the Earth's atmosphere and further cooling the Earth.
On the other hand, as the Earth warmed at the end of an ice age, the frequency of disturbances likely increased, releasing large amounts of carbon dioxide from the forest, and moving the boreal spectrum more towards the less carbon-intensive left side of the boreal spectrum. Warming the frozen peatlands also released huge quantities of methane, a greenhouse gas more than 20 times more powerful than carbon dioxide. These emissions would have contributed to the natural greenhouse effect, further warming the Earth.
UNDERSTANDING THE interaction of disturbance and succession gives clues about how the boreal forest might respond to climate change. Disturbance by fires, insects and storms largely determines the distribution of species within the boreal forest. The frequency of disturbance is closely linked to climate and can increase dramatically during warm, dry weather. On the other hand, the rate of succession can be significantly reduced by temperature, moisture or reproductive stress.
FIRE IS THE MOST important driving force in boreal ecology. It plays a crucial role in determining the distribution of boreal species, and improves forest vitality by removing trees weakened by age, drought, storm, insect infestation or extreme cold. Forest fires are frequently sparked by lightning, and usually only burn a small area of forest. Fires lead to increased diversity in the age and type of vegetation by opening up spaces in the forest. Fires also clear debris, expose the soil, improve the availability of nutrients and clear space for seedlings to grow.
[chart showing "Analysis of air trapped in Antarctic ice cores shows that methane and carbon dioxide contributions were closely correlated with the local temperature over the last 160,00 years. Present-day concentrations of carbon dioxide are indicated." omitted here.]
May, June and July are the main fire months in most boreal forests. Snow and cooler winter temperatures make fires less likely prior to this time, while autumn rains in August and September usually dampen fire activity afterwards.
Investigation of past fire frequency indicates that fire burns through tree stands about once every 50-100 years in Alaska and western Canada, once every 130 years in eastern Siberia, and once every 200 years in eastern Canada. Before fire suppression began in Sweden, fire occurred once every 80 years. In the last 200 years, Swedish fire suppression programmes have eliminated almost all fires.
The global area of boreal forest burned each year is highly variable, depending largely on the weather and the amount of fuel available in the form of litter and drought-stressed or otherwise weakened trees. Fires are most common during warm, dry weather.
Fire frequency plays a critical role in determining the distribution of species in the boreal forest. In cooler, moister areas with more than an average of 100 years between fires, fir and spruce tend to dominate. When fires occur more frequently - between every 50 and 100 years the faster growing, more fire- tolerant pines prosper. More frequent fires give the edge to aspen and birch. When fire returns more often than once every 10 years, no tree species can sustain itself, and the area becomes grassland.
Fire plays an important role in maintaining the limits of the forest. The cooling climate of the Little Ice Age, which lasted from 1250 to 1850, resulted in huge forest fires in northern Quebec. Most of the trees destroyed did not grow back and the result was the mixture of tundra and scattered trees that now characterize northern Quebec.
The grassy prairies on the southern limits of the boreal forest in western Canada covered an area significantly further north than today before European colonisation.
However, constant fire suppression has since allowed the forest to invade the northern grasslands and spread further south than would have naturally occurred.
Increased temperatures caused by climate change could lead to fire occurring well above natural frequencies, resulting in rapid shifts in boreal species and forest decline.
INSECTS PLAY A VITAL role in boreal ecology, decomposing litter and serving as a food supply for birds and small mammals. The forest usually benefits from insect outbreaks, because they reduce the likelihood of catastrophic fire by helping to eliminate older stands and diseased trees. However, populations of insects such as bark beetles, the Siberian silkworm and the spruce budworm can explode and devastate millions of hectares of forest. The life cycles of the spruce budworm (Choristoneura fumiferana) and the spruce bark beetle (Ips typographus) are strongly influenced by climate, with both species likely to increase in numbers during the kind of warmer, drier weather predicted in a global warming world.
[Chart showing "Fire Frequency and Species Distribution in the Boreal Forest" omitted here.]
The Spruce Budworm
THE SPRUCE BUDWORM is found throughout the southern boreal forest in North America. Its traditional range stretches from the Atlantic coast to the southern Yukon. A similar species, the western spruce budworm (Choristoneura occidentalis) can be found in the oroboreal forest throughout the Rocky Mountains. The spruce budworm is misnamed. It is not a worm, but the caterpillar larva of a moth. Its favourite food is fir, but it will also feed on spruce.
Major budworm outbreaks have occurred at thirty year intervals in eastern North America, which contains much of the continent's balsam fir. The most recent outbreak, which lasted from 1970 to the mid 1980s, resulted in the defoliation of 55 million hectares of forest - an area larger than France.
[Chart showing "North American Spruce Budworm Outbreaks" omitted here.]
The budworm attacks mature stands of fir. Budworm populations grow exponentially from year to year, and usually collapse only when every accessible tree has been defoliated. This often leads to the death of the trees. Although budworms normally attack fir, occasionally outbreaks will also occur in pure spruce areas of the forest.
Climate plays a major role in the size and duration of a budworm outbreak. Over several days, female moths can fly up to 600 kilometres to lay their eggs. Flights normally happen in the early evening in July and only occur if the evening temperature is above 18 degrees Celsius.
Cool evening temperatures discourage flights and lead to egg laying in a relatively small area of the forest. The hatched larvae may soon deplete their food supply and the outbreak would then collapse. On the other hand, warm summer nights may cause the outbreak to spread the following year.
The number of eggs laid by a budworm moth is determined by the average temperature. At 25 degrees Celsius, 50 percent more eggs are laid than at 15 degrees Celsius.
The development rate of the larvae is closely tied to temperature. Feeding rarely occurs at all if the temperature is less than 10 degrees Celsius. One of the major restrictions on the budworm's range may be that cool temperatures in the northern boreal forest do not allow the larvae to develop into moths fast enough to escape the autumn freeze.
The Spruce Bark Beetle
ONE OF THE MOST aggressive of boreal forest insects is the spruce bark beetle (Ips typographus). This insect is found throughout the boreal and temperate forests of Eurasia - from western Europe through to Korea and Japan. It normally attacks Norway spruce, but can also attack pine and larch.
Adult bark beetles hibernate in forest litter or in the bark of wind-fallen trees. Emergence is determined by temperature. Growing degree-days (the number of days above five degrees Celsius multiplied by the average temperature) must reach 50 to 130 before the beetles are able to emerge. The actual temperature must be above 20 degrees Celsius on the day of emergence. For this reason, beetles in northern Europe do not emerge until late May or early June.
In warmer areas of Europe, bark beetles are able to emerge earlier from hibernation and two or sometimes three generations of beetles can develop in a single season. In northern Europe, cooler temperatures normally constrain the beetles to a single generation.
Bark beetles normally exist at a low level in the boreal forest, living in trees that have been weakened by lightning strikes or disease. Large outbreaks are usually sparked by an increase in weakened trees. This can be caused by windstorms, forest fires, drought, or an attack by defoliating insects. Logging operations that leave waste wood behind in the forest can also cause outbreaks.
For example, a huge bark beetle outbreak in Europe at the end of World War II was caused by drought and poor logging practices. Large outbreaks in Japan on the northern island of Hokkaido followed extensive storm damage caused by typhoons in 1954 and 1981.
Once bark beetle populations grow to a critical size, they are able to overwhelm almost every mature tree, healthy or otherwise. Outbreaks can last for many years and normally collapse only when every tree within reach has been killed, or cold weather suppresses populations.
Like most other insects, bark beetles help maintain the long- term health of the forest. Their normal role in attacking diseased trees helps to improve forest vitality. Even during outbreaks, they can help promote the long-term growth of a forest by removing the overstory and allowing for the growth of the younger seedlings beneath.
STORMS AND LIGHTNING
WARMER TEMPERATURES CAN increase the frequency and intensity of storms and lightning.
Storms play an important role in shaping maritime boreal forests in northeastern Asia and North America. Typhoons are capable of destroying large areas of forest in northern Japan. Storms in both of these maritime regions create "wave forests" - strips of mature forest alternating with strips of underbrush or young forest developing in the aftermath of severe windstorms. Wave forests are also common in Newfoundland and the Appalachian mountains. Tornado activity plays a lesser role in disturbing boreal forests. In Ontario, storms destroyed approximately 10 percent of the forest area burned out by forest fires between 1950 and 1980. However, tornado activity has increased dramatically in North America since 1980.
Wind plays a critical role in magnifying the impact of other disturbances. Small forest fires can become larger conflagrations when fanned by gale-force winds. Windstorms can lead to blowdowns and generate large amounts of fuel for future fires or enough dead wood and damaged trees to encourage a bark beetle outbreak. Wind can also spread insects over long distances and so help to rapidly expand an outbreak. Conversely, fires and insect outbreaks can help increase the impact of a windstorm by creating exposed breaks in the forest. Lightning is the major cause of large forest fires, and plays a crucial role in driving fire and insect disturbances. Lightning is responsible for 38 percent of forest fires in Alaska, which in turn account for 80 percent of the total area burned.
SUCCESSION IN THE BOREAL FOREST
THE RATE OF SUCCESSION and recovery from disturbances depends on the level of stress. Stress comes from three main sources: temperature, moisture levels, and reproduction. Each of these are profoundly influenced by climate. In particular, high temperatures and dry soil can slow down or halt successions converting a disturbed forest to shrubs or grassland.
TEMPERATURE AFFECTS THE rate of respiration and photosynthesis. Healthy trees grow by accumulating carbon through photosynthesis at a rate faster than they lose carbon through respiration and other processes. In the absence of other factors, increasing the air temperature accelerates the rate of both. However, at high temperatures, the rate of respiration surpasses the rate of photosynthesis, causing a tree to lose carbon and eventually die.
TREES EXTRACT WATER and nutrients through roots, and lose water through transpiration. A similar process, evaporation, can dry forest soils. Evaporation and transpiration are strongly dependent on temperature. If a tree loses more water than it can absorb through its roots, it will dehydrate and die. Night temperatures also play a crucial role in relieving moisture stress. If night temperatures are too high, trees can die.
Spruce, pine and fir respond to moisture stress by closing tiny pores on their leaves or needles called stomates. With most transpiration taking place through the stomates, this can significantly reduce moisture stress. However, the stomates are also the pores which absorb carbon dioxide during photosynthesis. If the stomates are closed, photosynthesis stops and the tree may starve.
MANY BOREAL SPECIES are dormant during the autumn, and require a long period of winter chilling before warmer temperatures trigger budburst and new growth. Reduced chilling can significantly increase the time required for budburst.
Pollen and seed cones both develop very rapidly under high spring temperatures. However, this development may lead to abnormal and incomplete cones, with little pollen and infertile seeds. As a result, high spring temperatures can lead to reproductive failure.
Boreal seeds germinate within a specific range of soil temperatures. For example, black spruce seeds germinate between 15 and 28 degrees Celsius. If the soil temperature falls below 15 degrees, the processes that cause germination come to a halt. If soil temperatures rise above 28 degrees, bacteria and fungi can attack and consume seeds. The probability of germination also declines rapidly for higher temperatures.
Climate affects the boreal forest in many ways. In particular, warmer weather increases the frequency of disturbances and may decrease the rate of succession by creating temperature, moisture or reproductive stress. In a changing climate, the natural balance of the boreal forest would be expected to undergo profound disruption, with parts eventually reverting to grassland, some areas becoming more vulnerable to large-scale wildfires and insect outbreak, while some species could decline in the face of increasing stress.
Lighting the fuse: The Impact of Recent Climate Change on the Boreal Forest
The Heat is On
SCIENTIFIC EVIDENCE ALREADY shows that the climate is changing: average global temperatures have risen about 0.5 degrees over the last century, and the seven hottest years since records began 140 years ago all occurred after 1980. These temperature increases have been most dramatic at high latitudes. Summer temperatures on Ellesmere Island, in Canada's High Arctic, are higher than they have been for more than 1,000 years.
Weather patterns have changed at the closely monitored Experimental Lakes Area in the boreal forest of northwestern Ontario. Since the late 1960s, the average air temperature has risen by two degrees Celsius.
MAJOR FIRES HAVE recently disrupted the boreal forest. An area of boreal forest larger than France (56 million hectares) was destroyed between 1980 and 1989. Since 1976, the area burned in Canada has soared to six times the century trend, and to more than nine times the century trend in the alpine and temperate forest of the western US. Russian researchers have reported a sharp increase in the area of forest burned since 1985.
In 1989 the worst fires on record scorched western Canada, and the area east of James Bay in Quebec. Fire frequency has increased since 1975 in Alaska, and increased over several decades in Sweden at least until fire statistics were discontinued in 1980. Only in Finland has there been a decrease in the frequency and area of boreal fires.
[Three charts showing "Global Temperatures", "Canadian Temperatures", and "Western U.S. Forests Fires" omitted here]
In For The Kill
UNUSUALLY LARGE OUTBREAKS of the tree-eating insect, the spruce budworm, have devastated the Canadian boreal forest in recent years. A Canadian government study released in 1987 showed that conifers were growing on average up to 65 percent slower than in the 1940s and 1950s, because of budworm outbreaks, and possibly acid rain.
Spruce budworm outbreaks have grown exponentially throughout North America this century, with each outbreak doubling in size. The outbreaks following 1910, 1940 and 1970 affected 10, 25 and 55 million hectares respectively. The next outbreak, due by the year 2000, could affect 100 million hectares of forest. Such a huge infestation could dramatically accelerate the decline of spruce and fir in the southern boreal forest.
[Two charts "Russian Forest Fires" and "Tornado Trends for Canada" omitted here.]
METEOROLOGISTS REPORT A recent sharp increase in tornados in the U.S. and Canada. Canadian tornado frequency was four or five times higher than two decades earlier. Average wind speed in the Experimental Lakes Area in the central boreal forest of northwestern Ontario has increased by 50 percent.
1987, China: The Black Dragon Fire
WHEN THE FIRE CAME to Eastern Siberia, it was late April, 1987. Spring rain was light that year, and there had been little snow. Snow cover disappeared by early April, and much of the vast larch forest of eastern Siberia was tinder dry. The fires, mostly sparked by lightning, began east of Lake Baikal in the rugged Yablonovyy mountains and soon reached record size. Blown by gale-force winds, the fire reached the Amur river that separates Russia from China. Fires accidentally started by Chinese loggers were already raging to the south of the river.
After a fire was reported near Gulian on May 6, workers moved in to put it out. By 1:30 am on May 7, officials asked the Chinese Army for help. Despite an all-night effort, the fire spread towards the administrative centre of Xilinji. Soldiers raced gale-force winds to try to stop the fire from reaching the town's munitions depot. The flames leapt past the depot and consumed the town's lumber yard containing 100,000 cubic metres of wood. The soldiers did what they could to fight the inferno, but it was too late. Xilinji, a town housing twenty-two thousand people and largely built from wood, was destroyed by the flames.
More than 40,000 fire fighters battled the flames over the next 32 days until they were finally extinguished by rain in early June. In total, about 1.1 million hectares of Chinese forest was burned. North of the Amur, a much larger part of the Siberian forest was burned - at least 10 million hectares. It was one of the largest fires in recorded history.
It was not the forestry workers who were primarily to blame for starting the fires, and fire fighters weren't primarily responsible for putting them out. It was the weather.
Burning down the house
1988, USA: Yellowstone Forests Burn-out
WHEN THE FIRE CAME TO the US in the summer of 1988, Yellowstone National Park was gripped by the worst drought in its 112 year recorded history. Virtually no rain had fallen in June, July or August. Located high in the Rocky Mountains in northwestern Wyoming, Yellowstone is the oldest and most famous US national park. The Greater Yellowstone Area, which includes Yellowstone Park itself, Teton National Park, and six national forests, covers 2.9 million hectares. The peaks of the Rocky Mountains, large forests of lodgepole pine, and abundant moose, deer and bear, make it one of the US's most popular tourist attractions.
Strict fire suppression in the early days of the park had left Yellowstone with numerous old stands of lodgepole pine, many of which were now severely stressed by the drought. Many trees had already been killed by mountain pine bark beetle infestation.
There were 249 fires in the Greater Yellowstone Area in 1988 - about double the normal number. Most of these fires burned over a small area and extinguished themselves quickly. This kind of fire plays an essential ecological role in forest vitality by renewing the vegetation and eliminating dead forest litter. However, 50 of the fires spread much more quickly and with more intensity than normal. The situation was made worse because many of the big fires were accompanied by windstorms of hurricane intensity.
When Yellowstone Park officials realized how dangerous the situation was, they launched the largest forest fire suppression effort in US history. More than 25,000 fire fighters joined the battle. A squadron of airplanes and helicopters was used to fight the fires. Pilots from all over North America flew more than 100 aircraft to transport supplies and bombard the flames with water and chemical retardants.
As the fires approached Old Faithful, the famous Yellowstone geyser, the US Army was called in to help. Soldiers and civilian workers dug large fire lines through the forest removing trees and soil to deprive the flames of fuel and prevent spreading. Despite the best efforts of the US Park Service and the Army, more than 411,000 hectares of forest in the Greater Yellowstone Area were damaged by the fires. Almost half of the forest in Yellowstone National Park itself was scorched or consumed by the flames. The tourist industry directed their anger at the Park Service. Don Edgarton, manager of the photo shop at the Old Faithful tourist complex said "We've got ten million trees that are gone ... They ain't saving none of them ... We're sick about what's happened to the forest ..."
Park officials protested that they did everything that could have been done. Nothing could stop the roaring 60 metre wall of flame driven by windstorms of hurricane intensity. The winds sometimes blew embers and burning branches 2 kilometres in advance of the fire. No fire fighters could halt that kind of conflagration. It was not park officials or the US Army that determined the course of the Yellowstone fires. It was the weather.
1989, Canada: Worst Forest Fires on Record
WHEN THE FIRE CAME to the Canadian Province of Manitoba in 1989, it struck in more than a thousand places. Fires erupted from the shores of Lake Manitoba, and spread northward for 800 kilometres. High temperatures and drought over the previous two years had dried out many of the peat bogs and wetlands that served as natural barriers to fires. As a result, fires spread much more widely than usual. The inaccessibility of the area and sheer number of the fires made it difficult to deal with most of them. At the start of the season, the Manitoba government had only four people to handle fire management programs for an area of boreal forest the size of Germany. By the end of the season, more than 3,000 people were involved in a coordinated response to the flames. Specially constructed water tanks scooped up tonnes of water from northern lakes to dump on the flames - and still the fires grew. More fires were set off by lightning from thunderstorms generated by the huge clouds of smoke. Most affected were the indigenous Cree who have lived in Canada's boreal forest for thousands of years. Cree trap lines that had provided a living for decades were destroyed. Roaring flames leapt a kilometre across the Nelson River, forcing the evacuation of 4,000 people from the northern community of Norway House. As Air Force Hercules planes lifted thousands to safety, white and indigenous communities joined together to fight the fires. Rail and road transport links were cut off by the flames. By the time the autumn rains came, Manitoba had been hit by 1,140 fires, over six times more than usual. About 2.7 million hectares, or 5 percent of Manitoba's land area, had been consumed. More than 25,000 people from dozens of northern towns became refugees. Similar huge fires raged east of James Bay in Quebec and smaller fires struck Saskatchewan and Ontario. By the end of the year, about 6.4 million hectares of forest was destroyed. Amir Shabbar, a meteorologist with the Canadian Climate Centre, pointed out that there had been high tornado activity on the Canadian prairies and that the Arctic had been hit by an unprecedented heat-wave. The cause of the worst forest fires in Canadian history was clear. It was the weather. 
The 1990s: A Fiery Tempest
THE FIRES AND STORMS which ravaged the boreal forests in the late 1980s continue into the 1990s:
1990: MONGOLIA: On May 10, a huge fire destroyed more than 600,000 hectares of forest. 
RUSSIA: Eastern Siberia exploded into flames again. Gale-force winds of more than 100 kilometres per hour spread hundreds of fires over thousands of hectares of Siberian forest. Fires threatened the cities of Ulan Ude and Chita. 
USA: The worst forest fire in more than 50 years struck central Oregon. 
CANADA: The small town of Webequie, Ontario, was evacuated twice in one summer when fires burned through more than 60,000 hectares of forest. 
1991: CANADA: Fires in Quebec burn hundreds of thousands of hectares and cloak Atlantic Canada with thick smoke. 
RUSSIA: A state of emergency was declared in the southern Urals after a heat-wave sparked huge forest fires and widespread drought. 
1992: CIS: The worst drought in a century withered the new republics of the Commonwealth of Independent States. More than 19,000 forest fires flared across Russia. The sky over Moscow and St Petersburg was choked in smoke. Freak weather killed crops and destroyed tens of thousands of hectares of forest east of Lake Baikal. "In my whole life I can never remember such a thing happening," said one old peasant farmer. Inhabitants up to five kilometres away were evacuated when a forest fire caused the explosion of a huge weapons depot near Vladivostok in eastern Siberia. Fires burning in the contaminated forest near the Chernobyl nuclear power station created huge plumes of radioactive smoke that sent radiation levels soaring in parts of Belarus. 
USA: More than 150,000 hectares of forest were destroyed by mountain fires that spread to California, Nevada, Idaho, Oregon and Utah. The worst fire struck near Boise, Idaho. Cliff Wilcox, a spokesperson for the Boise National Forest, called it "a total ecological disaster".  One fire scorched 14,000 hectares at Burnt Mountain in Alaska's Arctic National Wildlife Refuge. When the threat forced the US Air Force to reveal the existence of ten nuclear-powered electricity generators, the public demanded their removal. 
1993: SIBERIA: July: 20,000 hectares blaze in the far northeast, fires burn around Khabarovsk on Siberia's Pacific coast and more than 50,000 hectares are destroyed near Irkutsk. 
USA: President Clinton declared a major disaster in November after 26 wildfires burnt out of control for over two weeks across 90,000 hectares of land stretching from the Mexican border to the northern suburbs of Los Angeles. A ten-kilometre-long wall of fire advanced through the LA suburb of Laguna Beach, destroying more than 600 homes. Damage was estimated at $950 million. 
Packing the Gunpowder: Destabilizing the Boreal Forest
OVER THE LAST CENTURY, research suggests that about one hundred billion tonnes of carbon released into the atmosphere by human activity has been reabsorbed by the world's forests. A significant amount of this carbon likely went into the boreal forest. This carbon absorption has helped to slow down the rate of climate change.
Many reasons have been put forward to explain why this carbon was absorbed. Regardless of the reason, there are alarming signs that this "carbon sink" is in decline, or has vanished altogether. In particular, increased stress caused by climate change and inappropriate forest management practices may be about to turn the boreal forest from one of the world's largest carbon sinks into one of the world's largest carbon sources.
THE MISSING CARBON
FOSSIL FUEL USE GREW rapidly after the mid-19th century. Carbon emissions from burning fossil fuels increased from half a billion tonnes in 1900, to one billion tonnes (1923), two billion tonnes (1955), four billion tonnes (1970), and are now approaching six billion tonnes. Between 1860 and 1988, fossil fuel burning released about 200 billion tonnes of carbon.
For much of the 19th century, temperate deforestation contributed more than 500 million tonnes of carbon dioxide to the atmosphere each year. Logging is now consuming some of the few scattered remnants of old-growth temperate forest. At the same time, logging and land clearing for agriculture continues to expand in the tropical and boreal forests, releasing more carbon into the atmosphere.
More forest is being cleared today than ever before. Most recent estimates say that roughly 1.6 billion tonnes of carbon were released from deforestation on average between 1980 and 1990. Between 1850 and 1990, around 120 billion tonnes of carbon were released into the atmosphere as a result of deforestation.
The total amount of carbon released from deforestation and fossil fuel use between 1850 and 1990 was therefore approximately 320 billion tonnes. However, less than half of this, about 130 billion tonnes, remained in the atmosphere. It is unclear what happened to the remaining 190 billion tonnes.
According to a recent analysis by Jorge Sarmiento from Princeton, about 90 billion tonnes of carbon was absorbed through general diffusion into the oceans. This is a natural process in which carbon dioxide in the oceans reaches a natural equilibrium with the atmosphere. Sarmiento estimates that this oceanic sink has been growing with the increase in carbon dioxide in the atmosphere, and now absorbs about 2 billion tonnes of carbon a year.
The remaining unaccounted-for 100 billion tonnes of carbon is the subject
of scientific controversy. Much of this missing or residual carbon is likely
to have been absorbed by forests. Some may also be stored in the oceans
in other ways.
ESTIMATED TOTAL CARBON BALANCE:
Fossil Fuels: 200 billion tonnes
Deforestation: 120 billion tonnes
TOTAL: 320 billion tonnes
Atmosphere: 130 billion tonnes
Ocean Diffusion: 90 billion tonnes
Residual Sink: 100 billion tonnes
TOTAL: 320 billion tonnes
ESTIMATED ANNUAL CARBON BALANCE:
Fossil Fuels: 5.4 billion tonnes
Deforestation: 1.6 billion tonnes
TOTAL: 7.0 billion tonnes
Atmosphere: 3.2 billion tonnes
Ocean Diffusion: 2.0 billion tonnes
Residual Sink: 1.9 billion tonnes
TOTAL: 7.0 billion tonnes
Note: The actual annual carbon budget varies from year to year. 
A recent literature survey concluded that the boreal forest absorbed about 0.7 billion tonnes of carbon on average each year during the 1980-1990 period. This suggests that the boreal forest makes up more than a third of the residual sink, and may be the largest single net terrestrial carbon sink. Although there is controversy over where and what it is, the size of the residual carbon sink can be estimated each year. It began to grow rapidly in the mid-1930s. However, detailed data from Charles David Keeling's research shows that the sink fluctuates dramatically from year to year, and has almost disappeared several times. Moreover, the running average sink size reacted a peak in the mid-1970s and has since been shrinking.
A recent abrupt increase in the size of the residual sink from 1992-93 is believed to be caused by the increased uptake of carbon dioxide by the oceans, most likely due to the temporary fertilization of aquatic plant life by iron from the Mt. Pinatubo volcano. It is not expected to continue.
If the shrinking of the residual carbon sink continues, it would have serious consequences because carbon dioxide levels would be much higher today if the residual sink had not absorbed 100 billion tonnes in the period since 1850.
The atmosphere already contains 10-15 billion tonnes more carbon than it would have if the residual sink had continued to grow after the mid-1970s instead of shrinking. The disappearance or substantial further reduction of the residual sink would cause a parallel accelerated build-up of carbon dioxide and more rapid climate change.
The Residual Sink
Many scientists find it surprising that there is a residual sink at all. Why would forests suddenly start to absorb increasing amounts of carbon after the 1930s? Three major theories have been put forward: carbon dioxide fertilization, nitrogen fertilization, and forest management practices.
Carbon Dioxide Fertilization
One common theory is that because carbon dioxide can act as a fertilizer promoting plant growth, forests are now growing faster because of the increased levels of carbon dioxide in the atmosphere. Most experiments on well-watered individual tree seedlings in laboratory conditions have shown that doubling carbon dioxide levels leads to an initial increase in growth of from 20-120 percent, with an average increase of 40 percent. Boreal tree species in laboratory conditions have shown an average short-term increase in growth of 38 percent.
In some cases, however, increasing carbon dioxide levels only promote temporary growth, and can even reduce growth if the concentration gets too high. For example, sweet gum and loblolly pine exposed to elevated carbon dioxide over four months were absorbing less carbon than control trees receiving normal levels of carbon dioxide. The decreased growth may have been caused by a build-up of starch in leaves and a reduction in photosynthesis. So it seems that increased carbon dioxide does not necessarily increase growth rate in all instances.
Moreover, increased levels of carbon dioxide may make some vegetation more vulnerable to insects.
Increased levels of carbon dioxide may also make vegetation more drought-resistant. Boreal trees other than larch normally respond to drought by cutting water loss by partially closing the stomates on the surface of leaves and needles. Since trees also absorb carbon Dioxide through these pores, severe drought can seriously reduce the level of photosynthesis and starve the tree. Increased levels of carbon dioxide might make it easier for plants to continue photosynthesizing, even with their stomates only partially open.
However, increased levels of carbon dioxide have also been shown to increase stomatal opening, which makes the plant vulnerable to moisture stress. Closing stomates will not necessarily make a tree more drought-resistant if increased levels of carbon dioxide have resulted in the growth of more or larger leaves or needles, and hence the growth of more water-losing stomates.
The response of vegetation to increased levels of carbon dioxide is strongly influenced by the abundance of other nutrients, particularly nitrogen. Boreal soils are nitrogen deficient, meaning that increased levels of carbon dioxide are likely to have little influence on tree growth. As a result, if carbon dioxide fertilization is having any real effect, it would largely be in temperate and tropical forests.
No studies have yet been published on the long-term effects of increased carbon dioxide on natural forests. This is unfortunate, because laboratory experiments leave out one of the most influential factors: competition between species. A review of the literature suggests that conifers, among other forest species, are least affected by increased levels of carbon dioxide. Most affected are underbrush shrubs and grasses. Faster growing underbrush could have a profound effect on the boreal forest. Underbrush can prevent conifer germination and crush or overshade seedlings. Grass can rapidly reduce soil moisture, especially for shallow-rooted species like spruce.
There is still no scientific consensus on whether increased levels of carbon dioxide have or could lead to increased long- term growth or increased resistance to moisture stress in natural boreal ecosystems. No studies have been conducted in natural ecosystems. There are, however, other explanations for the apparent increase in carbon absorption besides carbon dioxide fertilization.
Finnish researchers Kauppi, Mielikainen and Kuusela argue that nitrogen oxides in acid rain, although having many negative affects on trees, may have a temporary fertilizing effect, leading to at least a short-term carbon gain. They estimate that European forests, despite clear signs of decline, are still a net carbon sink absorbing from 85 to 120 million tonnes of carbon each year. However, they warn that continued acid rain and climate change may alter this situation.
The forest products industry sees natural forest disturbance as competition that consumes trees that could otherwise be logged. In response, industry and government have worked to replace the natural ecological dynamic of disturbance and succession with the artificial dynamic of forest management. Immense effort has gone into programs to suppress disturbances, including satellite surveillance, water bombing airplanes, toxic pesticides and sophisticated biological warfare. These programs have reduced the natural diversity of the forest and led to large areas of ageing coniferous forest. As a result, boreal and temperate forests have, over the last century, absorbed more carbon and released less carbon than they would have under normal conditions. However, this artificial carbon sink may now be gradually coming to an end as many ageing stands are no longer able to absorb more carbon, become more susceptible to blowdown from storms, and fire and insect outbreaks become increasingly difficult to suppress.
forest is presently
believed to be a sink for
atmospheric carbon, the
responsible for this sink
are not likely to be
Much of the residual carbon sink can be explained by a combination of these causes. However, these causes also point to an unstable sink. Carbon dioxide fertilization, if it exists, has natural limits. Nitrification may cause temporary fertilization, but increased acid rain is likely to lead to severe forest decline. Fire and insect suppression simply leads to ageing forests that are more fire and insect prone. There is clearly no guarantee that the residual sink will continue to expand, or even exist at all, in the future.
Although natural forces may even now be reducing the ability of the world's forests to absorb carbon dioxide and slow the rate of climate change, human intervention may destroy the global carbon sink even more rapidly. The world's forests are vanishing at an accelerating rate.
Tropical forests are disappearing at the rate of 17 million hectares a year, an area the size of the Netherlands every ten weeks.
The mid-latitude temperate forest has been reduced to a fragment of its original size, and now makes up only about one-eighth of the Earth's forest. Much of the temperate forest was destroyed with the expansion of Europe and subsequent European colonization of North America.
Human suppression of fire and insect outbreaks, and the creation of tree plantations have increased the area covered by temperate forest species since the late 19th century. However, much of this new forested area lacks the biodiversity of old-growth temperate forest. The few remaining areas of old-growth forest are now under extreme pressure from intensive logging operations.
Boreal Forest Under Siege
The boreal forest is now under attack by enormous clear-cut logging operations which remove the entire forest over huge areas. Corporations such as Mitsubishi, Daishowa, Weyerheuser, Noranda, and Repap have rights to clear-cut large areas of Canada's boreal forest. Some of these companies, including Hyundai, have begun logging operations in Siberia, which has the most boreal forest on the Earth.
Tree stands that have been clear-cut, even if replanted, will contain less carbon than old-growth stands. Consequently there is a net release of carbon to the atmosphere. Exposed soil on clear-cut land may decompose more rapidly, releasing more carbon.
A recent detailed analysis of the 1986 Canadian forest carbon balance by government researchers found that logging companies are cutting more than the net increase in forest biomass. The shrinking Canadian forest was reduced by 28 million tonnes from 1986-87. Nevertheless, the amount of logging continues to grow.
Clear-cut logging creates profound changes in the local forest climate, or microclimate. The barren area left behind by clear- cut logging is exposed to far more solar radiation than the floor of an old-growth forest.
A comprehensive study by the US Forest Service at a clearcut site in Montana found that clear-cutting exposed the forest floor to more than three times as much solar radiation as an uncut site, and almost twice as much as a site that had been partially cut with smaller trees left in place. Exposure sent surface temperatures soaring and dried out the soil. As a result, seedlings were exposed to intense temperature, moisture and reproductive stress. Survival was drastically reduced. Clear-cut logging also creates breaks in the boreal forest and can lead to more extensive wind damage during storms.
Shade-loving seedlings like spruce and fir do not often survive in clear-cut sites. As a result, tree planting programmes can fail and the site can revert to grass and shrubs. Eventually the area may be colonised by windblown seeds of sun-loving trees like aspen, birch and pine.
As a result of clear-cut logging operations, spruce and fir are rapidly disappearing from the many areas of the southern boreal forest. A recent Ontario study found that logging converted almost all former spruce and fir stands into stands dominated by broad-leaved species like aspen and birch. Global climate change will further contribute to the enormous stress clear-cut logging places on the boreal forest, accelerating the rate of forest decline.
Industry Argument False
The forest products industry often uses the argument that clear- cut logging mimics the natural fire disturbance common to boreal forests. This is a false argument. The vast majority of boreal fires are small fires that burn in the vegetation of the forest understory or remove only small areas of forest. Catastrophic fires that destroy large areas of forest are much rarer. Canadian fire statistics show that 50 percent of fires are less than 0.1 hectares in size, and 97 percent are less than 200 hectares.
Even the rare catastrophic fires do not often destroy all the trees in a stand, and can leave more than 30 percent of the trees still alive. Dead trees, or snags can be left standing for many years before they collapse. As a result, there is far more shade in a burnt site than in a clear-cut, lowering temperatures and sharply increasing the probability of seedling survival.
Plantations At Risk
Even when tree planting is successful on a clear-cut site, it does not recreate the original old-growth forest, but instead produces monoculture tree plantations. These plantations tend to be more prone to disturbances than more diverse old-growth.
Old-growth forests contain natural poisons and inedible species which resist insect attack. Forest entomologist Tim Showalter explains, "Old-growth forests with their very complex variety of different plant species are internally resistant to most problem insects." Plantations do not contain these repellents. The identical age stands in plantations create a dense even canopy which allows fires to spread rapidly. In contrast, a more diverse old-growth forest is likely to contain a more uneven canopy and scattered forest openings that reduce the likelihood of a large-scale fire.
Plantation trees may also be more affected by blowdown due to storms. According to plant physiologist Richard Tinus, "One of the risks in planting a tree is a deformed root system. We know that planted trees will not have the same configuration as trees grown from seed...". Poor root structures can lead to slower growth and blowdown in storms.
Because they are more susceptible to disturbances than natural forests, tree plantations and climate change may be an explosive combination.
Clear-cut logging leads to a net carbon release, produces forest areas
which are under enormous temperature, moisture and reproductive stress,
and often leads to the replacement of natural forest with disturbance-prone
tree plantations. For all of these reasons, clear-cut logging makes a significant
contribution to climate change and may contribute to rapid forest decline
with the continued emissions of greenhouse gases.
The Explosion: Computing a nightmare future
THE RECENT DRAMATIC changes in the boreal forest are associated with an average global warming of a fraction of a degree Celsius. Yet the IPCC predicts that temperatures three to nine times higher than this are expected in the next few decades if the levels of carbon dioxide in the atmosphere reach double pre- industrial concentrations. How will this enormous change affect the boreal forest?
The Earth's climate is an extremely complex system with wind, cloud, temperature, ocean current, vegetation, terrain, and the polar ice caps all interacting to determine the weather. Higher temperatures alter air and ocean circulation, the location and frequency of clouds, the distribution and vitality of terrestrial and marine ecosystems, and the area of glaciers and sea ice cover.
Fortunately, it is usually easier to forecast general climate trends than it is to make specific predictions about the next day's weather. Climate forecasts can be made using computer simulations of the atmosphere, called global circulation models or GCMs. Because GCMs require a long period of time and rapid, expensive supercomputers to make their calculations, there are very few in existence.
Certainly GCMs are not infallible. Currently they can only deal effectively with large areas of land and water, and cannot yet realistically simulate the ocean. "Feedbacks" are implemented differently in each GCM, and so temperature and precipitation predictions sometimes differ, especially on a regional basis.
Despite these difficulties, GCMs are still the best tool available for predicting the impact of increased levels of greenhouse gases. Their success in simulating current and past Earth climates is growing, and there is increasing confidence in their predictions. In the absence of a second Earth-like planet to experiment with, they offer the only method available for predicting the effects of climate change.
Catastrophic Decline Predicted
ONE OF THE MORE comprehensive GCM studies was published in 1992 by Shugart and Smith from the University of Virginia, and Leemans from the International Institute for Applied Systems Analysis in Austria.
"There seems to be a
that both structure
and functions of boreal
regions will be drastically
altered by the climate
by present global
Comparing results using climate-vegetation models tied to the outputs of four different GCMs, these researchers assumed a doubling of atmospheric carbon dioxide levels. The results derived from all four GCMs predicted massive decline in the existing boreal forest. The OSU GCM results projected a 50 per cent decline; others projected more extreme impacts, with the GFDL GCM implying a 90 percent decline.
While the models predicted that some new forest would move into the northern tundra, this new growth would cover a smaller area than the forest displaced to the south, reducing the total size of boreal forest and its capacity to act as a carbon sink.
Mapping the Climate
SEVERAL DECADES AGO, L.R. Holdridge observed a close correlation between climate and vegetation distribution. Based on temperature and precipitation, he developed a system of 37 global life zones. Holdridge's life zones system is a useful tool for predicting the impact of climate change because it can describe the distribution of a wide variety of vegetation based on simple variations in temperature and precipitation.
[Four maps with the following caption are omitted here:
"THESE MAPS SHOW the expected response of the boreal forest to the climate change projected by general circulation models as a result of doubled levels of carbon dioxide. The original maps have been simplified to focus only on the boreal forest, and have been adapted to show how the existing forest is projected to change.
General circulation models are not yet accurate at the regional level. These maps are intended to show the scale of potential impacts on the forest, and are not likely to be accurate in detail within specific regions. We have chosen two substantially different models to show the range of potential impacts.
The OSU model projects the disappearance of 50% of the existing forest. The GFDL model projects the disappearance of over 90% of the existing forest." ]
The boreal forest forms a unified ecosystem with a distribution determined by climate. However, each species of vegetation found in the forest responds slightly differently to changes in temperature and precipitation. E.O. Box recognized this and developed a modification of Holdridge life zones that allowed for several species in each life zone. Cramer and Leemans used Box's model and the OSU GCM to compare the impact of doubled levels of carbon dioxide on evergreen conifers such as spruce and pine, which dominate in North America and Europe, and deciduous conifers such as larch, which dominate in Siberia. This research projected a 66 percent decline in existing evergreen conifers, and a 31 percent decline in existing deciduous conifers. Most notably, spruce and pine disappear almost entirely in Scandinavia.
STATIC VEGETATION models such as the Holdridge life zones do not provide detailed information on how the forest will change or decline. Instead, a number of more complex succession simulation models have been developed to examine this. These succession models include the impact of soils, drainage, inter-species competition, shading, and other factors. The models must deal with the fact that the projected climate change is at least 15-30 times faster than any previously known. In many cases, seedlings that sprout in one kind of climate will come to maturity in an entirely different climate, putting great stress on the forest.
Succession models are complex and require an enormous amount of computation. For this reason, most published results look at a few specific sites. One exception is a series of maps produced by Overpeck and Bartlein showing changes in the distribution of various species in eastern North America under doubled levels of carbon dioxide. The results are consistent with predictions from static vegetation models and show a severe decline in conifers, especially spruce, coupled with some forest growth into the tundra.
THE DECLINE OF MUCH of the southern boreal forest may be driven by increases in drought and fire frequency. For example, the soil in many parts of the boreal forest may dry out because increased temperatures will lead to more evaporation. This is likely to happen even if there is more snow, as some GCMs project. Warmer winters may lead to earlier springs with longer periods of warm weather giving more time for snow to melt and evaporate, leading to drier summers and increased drought.
Two areas of the boreal forest are especially prone to an increase in drought: the region around east of Lake Baikal in Siberia, and the western Canadian provinces of Alberta, Saskatchewan and Manitoba. Most GCMs project significant drought in these areas. Much of the oroboreal forest in the Rocky Mountains may also be replaced by scrubland or grassland.
Fire would rapidly accelerate the conversion of drought-stricken forest to grassland. NASA scientists Colin Price and David Rind found that doubling carbon dioxide levels would lead to a 26 percent increase in lightning strikes. Warmer weather would also add to atmospheric turbulence, increasing the intensity and frequency of windstorms, turning ordinary forest fires into roaring infernos.
Based on an examination of the results of three different GCMs, Flannigan and Van Wagner concluded that climate change would increase Canada's annual fire severity rating by about 46 percent. However, this study may be an underestimate because it did not consider changes in lightning frequency or in the length of the forest fire season. In a follow-up study, Wotton and Flannigan concluded that the Canadian fire season would increase by more than 20 percent.
Insects and Competition
IN SOUTHERN AREAS OF the boreal forest where increased temperature does not lead to decline into grassland, conifers will suffer from insect outbreaks and increased competition from temperate broad-leaved species like maple and oak. Spruce is especially sensitive to warm weather. A study of boreal forest around Stockholm, Sweden, predicts the complete disappearance of spruce due to warm winters. A similar study of eastern North America shows a retreat of spruce to the shores of Hudson Bay and part of northern Quebec.
Conifers would be extremely vulnerable to insect outbreaks, and spruce budworm and bark beetle outbreaks would be strongly encouraged by warmer temperatures. Increased drought could change the effect of storms and insect outbreaks. Instead of encouraging the growth of conifer seedlings by removing the forest overstory, storms and insect outbreaks could create large amounts of fuel for more frequent fires, transforming many spruce and fir stands into grassland or stands dominated by pine or boreal broad-leaved trees. Higher temperatures are also likely to decrease the reproductive success of many conifers, making it less likely that conifer stands will be able to recover from major disturbances.
A computer simulation of responses to climate change in the boreal forest of interior Alaska also predicted a diverse response. Climate warming in poorly drained north slopes would convert a cold black spruce forest into a warm mixed deciduous and spruce forest. Warming of a well drained south slope would lead to a dry aspen-dominated forest or even the formation of grassland.
This patchwork response is consistent with federal researchers' projections for the Canadian boreal forest. Their study concluded that much of the boreal forest in Ontario and southern Quebec will decline into a patchwork of grassland and temperate forested area, or transitional grassland.
Climate change is likely to drive the southern boundary of the boreal
forest northwards much more rapidly than the migration rates of temperate
trees, such as maple and oak. As a result, much of the southern boreal
forest may be reduced to a degraded ecosystem of shrubs and scattered stands
of aspen and birch.
INTERACTION WITH ACID RAIN and air pollutants may worsen forest decline and lead to the development of grassland or degraded forest where climate models alone might suggest the development of temperate forest. Surveys in Finland, for example, reveal an acid-rain-linked decline in lichen over an area of more than 10 million hectares. 
Lichens play a crucial role in the moisture and thermal regimes of forest soils. A lichen mat reduces moisture stress and allows trees to exist on soil that would otherwise be too dry to support growth. Because lichens have high reflectivity and low thermal conductivity, they also insulate the underlying soil from heat. A 12 cm deep lichen mat can reduce the soil heat flux by almost 50 percent.  An important effect of the lichen decline may be to dry out the soil and increase the frequency of drought. ________________________________________________
Expansion Into Tundra
THE ARCTIC TUNDRA is particularly vulnerable to climate change. Vegetation models based on the GFDL and UKMO GCMs predict the complete disappearance of the existing tundra if atmospheric carbon dioxide levels double. Modeling based on the OSU and GISS GCMs predicts the disappearance of 75 percent of the existing tundra. Although melting polar ice is expected to allow the development of new tundra closer to the pole, all models predict a drastic overall reduction.
The major reason for the shrinking of the tundra is the northward expansion of the boreal forest. The tree-line where the forest meets the tundra is strongly influenced by climate and has moved long distances in the past. Tree growth within the existing forest-tundra transitional zone may occur quickly because tree stands are already widely dispersed and can expand rapidly. However, movement of the tree-line further north into the tundra is likely to happen more slowly.
The fossil pollen record shows that past migration rates were far slower than the changes predicted for the future climate. Spruce, for example, has responded to past climate change by expanding its range by 80-500 metres per year. Fir has moved about 20-300 metres per year, while pine has moved more rapidly, by about 1,500 metres per year.
On the other hand, climate-vegetation models suggest shifts in the boreal forest of 500 kilometres or more in less than a century. This works out to 5,000 metres per year or more than 10 times the historic migration rates of most boreal species. It may take the boreal forest several centuries to expand as far north as some models predict the climate will allow.
"The carbon pulse could
release as much as
225 billion tonnes -- or
almost one-third of all
the carbon now in the
The Ozone Threat
THE NORTHWARD EXPANSION of the boreal forest is likely to be delayed by exposure to ultraviolet radiation because of ozone depletion. While an ozone hole has not yet developed over the northern hemisphere, increasing greenhouse gases could in future further lower Arctic stratospheric temperatures enough for this to happen. The boreal forest - and the one billion people that live to its south - would be exposed to sharply increased levels of ultraviolet radiation.
Studies show that ultraviolet radiation negatively affects seedling growth. For example, three-year-old loblolly pine seedlings exposed to ultraviolet radiation grew 20 percent less than similar unexposed plants. A similar study on other seedlings found that UV-B reduced jack pine biomass by about 25 percent, and reduced white spruce and black spruce biomass by about 50 percent.
Unfortunately, phasing out all ozone depleting substances will not be enough to prevent a hole in the northern ozone layer. Enough ozone destroyers will remain in the atmosphere to cause serious ozone depletion for at least a century.
The Carbon Pulse
Increased stress and disturbances are likely to destroy existing boreal forest much more quickly than new boreal forest can expand onto tundra, or temperate forest can expand into former boreal areas. Moreover, warmer temperatures will have an immediate impact on the rate of soil decay, and the subsequent increased rate of soil carbon release into the atmosphere.
As a result, many studies project a massive net release of carbon into the atmosphere - a "carbon pulse". A recent study on the implications of a doubling of carbon dioxide levels concluded that forest dieback, mostly in the boreal forest, could release 70 to 130 billion tonnes of additional carbon into the atmosphere. Another study found that the carbon pulse could release as much as 225 billion tonnes of carbon - or almost one third of all the carbon now in the Earth's atmosphere.
The accelerated rate of climate change caused by the carbon pulse could cause further carbon release, and hence even more rapid climate change - a potentially catastrophic positive feedback.
An unknown factor is the response of peatlands to climate change. Peatlands, which cover a fifth of the boreal forest, store almost two-thirds of its carbon - 419 billion tonnes out of a total 709 billion tonnes. Peatlands are currently a minor net carbon sink, absorbing about 45 million tonnes of carbon each year. However, they are a significant source of methane, a greenhouse gas that is 21 times more powerful than carbon dioxide.
Rising temperatures could dry out southern peatlands and reduce methane emissions. However, warmer conditions could also melt tundra and permafrost in the north and release huge quantities of methane into the atmosphere. Fire could also speed up the release of large amounts of carbon from dried-out southern peatlands. Clearly more research is necessary on the role of peatlands in the carbon cycle.
IT IS DIFFICULT to predict the detailed impacts of climate change on the boreal forest. However, the oroboreal forest located high in the Rocky Mountains is already being devastated by the warming climate in one particular area.
The severe drought that continued into 1992 in Nevada and California provided a frightening glimpse of the ecological destruction that lies ahead if human-enhanced climate change is not redressed. In addition to drought-encouraged fires, the six long years of little or no rain had dried up manmade reservoirs and natural trout streams and reduced streams to a trickle, destroying more than 90 percent of wildfowl nesting areas, and killing deer, wild horses and bears. Thousands of hectares of forest gradually weakened by the years of drought, succumbed to insects and disease.
Disarming the Carbon Bomb: Positive Solutions for Stabilizing the Climate and Saving the Forest
GREENPEACE BELIEVES that the only effective and direct way to stabilize the climate is by sharply reducing anthropogenic greenhouse gas emissions from fossil fuel use and deforestation. Catastrophic climate change and a severe decline in the boreal forest can only be prevented by stopping the build-up of greenhouse gases in the atmosphere. This will require three major policy initiatives.
1. PHASE OUT FOSSIL FUELS
THE IPCC ESTIMATES that current fossil fuel and energy use trends will result in a doubling of 1990 greenhouse gas emissions by about 2030, and a quadrupling by the year 2100. The IPCC concluded that the only way to prevent a rapid build-up of greenhouse gases is to cut emissions by 6080 percent from 1990 levels, which amounts to a 95 percent cut from projected emissions in the year 2100. The only way to achieve such radical cuts in greenhouse gas emissions is to phase out fossil fuels. The fossil fuel industry often claims that a large-scale change in the global energy system is impossible.
A recent detailed study released by Greenpeace International shows that phasing out fossil fuels is entirely practical and proves the fossil fuel industry wrong. The study examined renewable "clean energy" sources such as wind turbines, solar photovoltaic panels, biomass energy crops, geothermal power, and small-scale hydro-electricity alternatives. It concluded that enough renewable clean energy is available to replace current fossil fuels and nuclear power, even under UN and World Bank forecasts in which the world population doubles and the global economy expands 14 times its present size. The fossil fuel phase-out would be easier to achieve if such upward population and economic trends are stabilized at ecologically sustainable levels.
The Greenpeace study assumes that clean energy technologies would only be adopted when cost-effective. Energy bills are not expected to rise higher than they are now. Using conservative assumptions, fossil fuel use can be cut in half by 2030 and eliminated by 2100.
Phasing out fossil fuels will not be easy. It will take major changes in public and private sector policy. But there is no credible alternative if the world is to avoid irreversible climate change.
Phasing out fossil fuels will also eliminate acid rain, smog, and other
forms of air pollution that are causing forest decline.
1. Cut Subsidies for Dirty Energy
About 80 percent of OECD government spending on energy research and development goes on non-renewable and highly polluting fossil fuels and nuclear power. This money should be used to research the efficient use of renewable energy.
Billions of dollars of taxpayer money is spent on giving tax breaks and subsidies to fossil fuel exploration and marketing. Still more billions are spent on unnecessary road construction. These taxpayer funded subsidies should be cut or transferred into spending on mass public transit.
2. Ban Inefficient Products
Masses of energy are currently wasted through the inefficient use of gas guzzling cars, heat losing building, unnecessary and energy inefficient appliance, and out-dated industrial processes. Instead of this power madness tough standards are necessary to outlaw poorly designed products, and training programmes to ensure industry moves to producing and using efficient technology as soon as possible.
3. Energy Sector Reforms
Most of today's electricity and gas companies make their profits by selling as much energy as possible. This inevitably leads to the inefficient use of energy produced as cheaply as possible - with prices that do not take into account the environmental damage and costs of fossil fuels and nuclear power. Energy sector reforms are necessary to:
* include the environmental and social costs of energy in prices;
* invest in reducing energy consumption rather than building new power stations or pipelines;
* purchase more power from small-scale sources rather than destructive energy mega-projects.
These reforms will allow companies to phase in the more efficient use of more expensive renewable energy. As a result, overall energy bills will not change. These reforms are still compatible with profits for shareholders. A number of US utilities are already operating using similar principles, sometimes called Integrated Resource Planning.
4. Better Urban Planning
Urban sprawl must be stopped. The trend should be towards smaller cities
with a higher population density. Cars should be excluded from most or
all of each city, and replaced with a fast, efficient mass transit system.
Cities should be connected by a rapid rail system.
2. SAVE THE FORESTS - STOP DEFORESTATION
AT THE CURRENT RATE of deforestation, most of the world's natural forests will be gone in a few decades. This would result in the elimination of much of the Earth's ability to regulate the climate by absorbing carbon dioxide. It would also result in a massive additional release in carbon.
Clear-cut logging should be halted in temperate and boreal forests. Logging should proceed only on ecologically-defined principles which preserve the forest ecosystems. Clear-cuts followed by planting monoculture tree farms do not preserve the forest or biodiversity.
Much of the logging in temperate and boreal forests is to produce pulp for unnecessary paper and packaging. Sharp reductions in packaging, combined with the extensive use of recycled paper, should eliminate the need for most of the pulp now being produced. Changing to more labour-intensive selective logging practices and switching to the production of more value-added forest products such as furniture should result in the disturbance of far less forest with no loss of employment in the forest industry.
At present, tropical deforestation is being driven by inappropriate aid and economic development programmes that fail to offer poor people living in developing countries a decent standard of living. Aid and development programs must be changed so that they no longer contribute to tropical deforestation.
Some 200 million indigenous people live in the world's forests. They are often in the front line of defence against deforestation. Upholding the rights of these people to their lands and livelihoods is the key to stopping deforestation.
Carefully designed labour-intensive reforestation programmes should be introduced by all sectors to restore natural forest ecology. Monoculture tree plantations are not reforestation.
3. BAN HALOCARBONS
HALOCARBONS SUCH AS CFCs and HCFCs are greenhouse gases that also destroy the ozone layer. They should be banned immediately. HFCs are not acceptable replacements for CFCs because they are potent greenhouse gases. Acceptable replacements are already available for virtually all uses for halocarbons. There is no excuse for not using these replacements immediately.
1 Cited in Harrison E. Salisbury, The Great Black Dragon Fire: A Chinese Inferno, Little, Brown and Company, 1989.
2 Intergovernmental Panel on Climate Change, Report to IPCC from Working Group 1: Policymakers' Summary of the Scientific Assessment of Climate Change, June 1990, p. XIV.
3 Charles D. Keeling, et al., A three-dimensional model of atmospheric CO,) transport based on observed winds: Analysis of observed data, in David H. Peterson (ed.), Aspects of Climate Variability in the Pacific and the Western Americas, Geophysical Monograph 55, American Geophysical Union, 1989.
4 Peter M. Vitosek, Global Environmental Change: An Introduction, Annual Review of Ecological Systematics, 23:1149 1992.
5 IPCC 1990, op.cit., p. xv.
6 Greenpeace International, The Climate Time Bomb, Greenpeace International, June 1994.
7 IPCC 1990, op.cit. and Intergovernmental Panel on Climate Change, Climate Change 1992: The Supplementary Report to The IPCC Scientific Assessment, Cambridge University Press, 1992.
8 IPCC 1990, op.cit., p. 300.
9 Jeremy Leggett, Global Warming .. the Worst Case, Bulletin of Atomic Scientists, 85: 28-32, 1992.
10 Allen M. Solomon and Wolfgang Cramer, Biospheric implications of global environmental change, in Allen M. Solomon and Herman H. Shugart (eds.), Vegetation Dynamics and Global Change, Chapman and Hall, New York, 1993, p. 41.
11 IPCC 1992, op.cit., p. 31.
12 W.M. Post, Uncertainties in the Terrestrial Carbon Cycle in Allen M. Solomon and Herman H. Shugart, Vegetation Dynamics and Global Change, Chapman and Hall, New York, 1993.
13 IPCC 1990, op.cit., p. 10.
14 Mark E. Harmon, et al., Effects on carbon storage of conversion of old-growth forests to young forests, Science, 247:699-702, 1990.
15 Charles F. Cooper, Carbon storage in managed forests, Canadian Journal of Forest Research, 13:155-166, 1983.
16 Gordan B. Bonan and Herman H. Shugart, Environmental factors and ecological processes in boreal forests, Annual Review of Ecological Systematics, 20:1-28, 1989.
17 For information on the boreal forest in Japan, see A. Miyawaki and R. Tuxen (eds.), Vegetation Science and Environmental Protection, Maruzen Co. Ltd., Tokyo, 1977.
18 FAO, Forest Resources 1980, FAO, 1985.
19 Ibid. For the purpose of this calculation, boreal forest was considered to be roughly equivalent to coniferous forest in northern countries.
20 IPCC 1990, op.cit., p. 300.
22 T. Webb and P.J. Bartlein, Global changes during the last 3 million years: Climatic controls and biotic responses, Annual Review of Ecological Systematics 23:141-173, 1992.
23 M.J. Apps, et al., The changing role of circumpolar boreal forests and tundra in the global carbon cycle, Water, Air and Soil Pollution, (in press), 1993.
24 E.E. Wheaton, et al., An exploration and assessment of the implications of climatic change for the boreal forest and forestry economics of the Prairie Provinces and Northwest Territories: Phase One. SRC Technical Report No. 21 1, Environment Canada, Atmospheric Environment Service, 1987.
25 S. Tyhknen, A circumpolar system of climatic-phytogeographical regions, Acta Bot. Fenn., 127:1-50, 1984.
26 P.V. Wells and J.D. Stewart, Cordilleran-boreal taiga and fauna on the central Great Plains of North America, 14,00018,000 years ago, American Midland Naturalist, 118(l): 94106, 1987.
27 For maps of these changes, see J.C. Ritchie and G.M. MacDonald, Patterns of post-glacial spread of white spruce, Journal of Biogeography 13:527-540, 1986
28 The close correlation between temperature and atmospheric greenhouse gas levels can be seen in the famous Vostok ice core. See IPCC 1990, p. I I and p. 18.
29 J.S. Rowe and G.W. Scotter, Fire in the boreal forest, Quaternary Research, 3:444-464, 1973; and Leslie A. Viereck, Wildfire in the taiga of Alaska, Quaternary Research, 3:465495, 1973.
30 Shigeru Uemura, Satoshi Tsuda and Sakae Hasegawa, Effects of fire on the vegetation of Siberian taiga predominated by Larix dahurica, Canadian Journal of Forest Research, 20:547-553, 1990.
31 0. Zackrisson, Influence of fires on the North Swedish boreal forest, Oikos, 29:22-32, 1977.
32 M.D. Flannigan and C.E. Van Wagner, Climate change and wildfire in Canada, Canadian Journal of Forest Research, 21(l):66-72, 1991.
33 Ross W. Wein, Effects of fire in the boreal forest, Boreal Forest Conference Proceedings, Athabasca University, 1992.
34 Serge Payette and R. Gagnon, Late Holocene deforestation and tree regeneration in the forest-tundra of Quebec, Nature, 313:570-572, 1985.
35 Rowe and Scotter 1973, op.cit., p. 460.
36 JR. Blais, The ecology of the eastern spruce budworm: a review and discussion, in Recent advances in spruce budworms research: proceedings of the CANUSA spruce budworms research symposium, Bangor, Maine, September 16209 1984.
37 R.B.B. Dickison, Eastern spruce budworm larval development and behavior, adult dispersal, and efficacy of control methods, in Climate Applications in Forest Management and Forest Production: Proceedings of Forest Climate 86, Environment Canada, 1988, pp. 165-170.
38 Jacques Rignihre, An oviposition model for the spruce budworm, Choristoneura fumiferana (Lepidoptera: Tortricidae), Canadian Entomologist 115:1371-1382, 1983.
39 W.J.A. Volney and H.F. Cerezke, The phenology of white spruce and the spruce budworm in northern Alberta, Canadian Journal of Forest Research, 22(2):198-205, 1992.
40 Erkki Annila, Influence of temperature upon the development and voltinism of Ips typographus L. (Coleoptera, Scolytidae), Ann. Zool. Fennici, 6:161-208, 1969.
41 Ibid., p. 203.
43 Clark L. Lovelady, et.al., Relation of lightning to herbivory by the southern pine bark beetle guild (Coleoptera: Scolytidae), Environmental Entomology 20(5):1279-1284, 1991.
44 Erik Christiansen and Alf Bakke, The spruce bark beetle of Eurasia, in A.A. Berryman (ed.), Dynamics of Forest Insect Populations, Plenum Press, New York, 1988.
45 K. Furuta, A comparison of endemic and epidemic populations of the spruce beetle (Ips typographus japonicus Niijima) in Hokkaido Journal of Applied Ecology, 107:289-295, 1989.
46 Kenneth F. Raffa, The Mountain Pine Beetle in Western North America, in A.A. Berryman (ed.), Dynamics of Forest Insect Populations, Plenum Press, New York, 1988.
47 J.T. Overpeck, D. Rind and R. Goldberg, Climate-induced changes in forest disturbance and vegetation, Nature 343:5 1 53, 1990; Colin Price and David Rind, Lightning activity in a greenhouse world, in American Forestry Association, Proceedings of the 11th Conference of Fire and Forest Meteorology, April 16-19, 1991, Missoula, Montana. 48 Furuta 1989 op.cit.
49 Alexander Robertson, Some effects of wind on northern forests in a changing climate, Commonwealth Forestry Review, 70(1/2):47-55, 1991.
50 James B. Harrington and Michael J. Newark, The interaction of a tornado with rough terrain, Weather, 41:310-318.
51 David Etkin, Tornado climatology, Climatic Perspectives, Atmospheric Environment Service, Environment Canada, October 1993, pp. 10-13; Edward Ferguson and Frederick Ostby, Tornadoes of 1990: An Al] Time Record Year, National Severe Storms Forecast Center, USA, Weatherwise, 44(2):19-28, April 1991.
52 Price and Rind 1991, op.cit..
53 Brian J. Stocks, The extent and impact of forest fires in northern circumpolar countries, in Joel S. Levine, ed., Global Biomass Burning: Atmospheric, Climatic and Biospheric Implications, The MIT Press, Cambridge, Massachusetts, 1991, pp. 197-202.
54 R.J. Day and R.G. Butson, Seedling-water relationships after outplanting, in Climate Applications in Forest Management and Forest Production: Proceedings of Forest Climate 86, Environment Canada, 1989, pp. 55-62.
55 M.G.R. Cannell and R.I. Smith, Thermal time, chill days and prediction of budburst in Picea sitchensis, Journal of Applied Ecology, 20:951-963, 1983, and M.G.R. Cannell and R.I. Smith, Climatic warming, spring budburst and frost damage on trees, Journal of Applied Ecology, 23:177-191, 1986.
56 Stephen D. Ross, Temperature influences on reproductive processes in conifers, in Climate Applications in Forest Management and Forest Production: Proceedings of Forest Climate 86, Environment Canada, 1988, pp. 40-43.
57 R. Alan Black, Reproductive biology of Picea Mariana (Mill.) Bsp. at treeline, Ph.D. Thesis, Department of Botany, University of Alberta, 1977; and R. Alan Black and L.C. Bliss, op.cit., p. 349.
58 Robert E. Dickinson and Ralph J. Cicerone, Future global warming from atmospheric trace gases, Nature, 319:109-115, 1986.
59 Climate News, World Meteorological Organization, 2, Jan 1993.
60 R.M. Koerner and D.A. Fisher, A record of Holocene summer climate from a Canadian high-Arctic ice core, Nature, 343:630-631, 1990.
61 D.W. Schindler, et al. Effects of climatic warming on lakes of the central boreal forest, Science, 250:967-970, 1990.
62 Stocks 1991, op.cit.
63 Allan N.D. Auclair and Thomas B. Carter, Forest wildfires as a recent source of CO? at mid-high northern latitudes, Canadian Journal of Forest Research, 23: 1528-1536, 1993 .
64 Olga N. Krankina, Forest fires in the former Soviet Union: Past, present and future greenhouse gas contributions to the atmosphere, in: Ted S. Vinson and Tatyana P. Kolchugina (eds.), Proceedings of the International Workshop on Carbon Cycling in Boreal Forest and Sub-Arctic Ecosystems, U.S. Environmental Protection Agency, Global Change Research Program, 1991.
65 Stocks, 1991, op.cit.
66 "Severe drop in tree growth rate found", Toronto Star, January 30, 1987.
67 Blais 1984, op.cit.
68 Etkin 1993, op.cit.
69 Schindler 1990, op.cit.
70 Most of the information in this section is taken from Harrison E. Salisbury, The Great Black Dragon Fire: A Chinese Inferno, Little, Brown and Company, 1989.
71 C.W. Philpot, The Wildfires in the Northern Rocky Mountains and Greater Yellowstone Area - 1988, Transactions of the 55th North American Wildlife and Natural Resources Conference, 1990, pp. 185-187.
72 Most of this information is from Gregory Vogt, Forests on Fire: The Fight to Save Our Trees, K. Watts, New York, 1990.
73 Information from this section taken from Maureen Brosnahan, "After the inferno: Northern Manitoba slowly comes back to life one year after the worst forest fires on record", Canadian Geographic, December 90/January 91, pp. 69-75, and the Winnipeg Free Press: "Fire emergency declared as 18,000 flee from homes". July 24, 1989; Sifting the Ashes series, September 6, 7, 8, 12; ... Unprecedented' weather cited in record forest fires", September 28, 1989.
74 "Fire in Mongolia burns 600,000 hectares of forests", Xinhua, May 26,1990.
75 "Forest fires rage in Trans-Baikal area", Tass, May 17, 1990; "Forest fires continue raging in Buryat Republic", Tass, May 18, 1990.
76 "Oregon fire", AP, August 6, 1990.
77 "Department of National Defence Notice to the Media", August 24, 1990.
78 "Quebec forest fires send smoke to Maritimes", Reuter, June 27, 1991.
79 "Russian farmland hit by drought and forest fires", Reuter, July 2, 1991. "Forest blaze in Soviet Far East defeats firefighters", Reuter, May 5, 1991.
80 "Forest fires in CIS rage during worst drought in 100 years", IPS, August 25, 1992; "Huge blast at Russian Pacific Ammunition Depot", Reuter, March 24, 1992; "Soviet-fires", AP, August 14, 1992.
81 "Fires Continue Rampage Through Drought-Stricken California", Reuter, August 23, 1992.
82 "Air force generators exposed by wildfire", Anchorage Daily News, September 27, 1992.
83 Lloyd's List, 20 August 1993.
84 Lloyd's List, 20 November 1993.
85 Keeling 1989, op.cit., p. 187.
86 R.A. Houghton, Effects of land-use change, surface temperature, and C02 concentration on terrestrial stores of carbon. Paper presented at the IPCC/WHRC workshop, Biotic Feedbacks in the Global Climate System, Woods Hole, October 1992.
87 Keeling 1989, op.cit., p. 192.
88 Jorge L. Sarmiento, et al, A perturbation simulation of C02 uptake in an ocean general circulation model, Journal of Geophysical Research, 97(C3):3621-3645, 1992.
89 The annual average figures are cited in J.L. Sarmiento and E.T. Sundquist, Revised budget for the oceanic uptake of anthropogenic carbon dioxide, Nature 356:589-593, 16 April 1992
90 M.J. Apps, et al., The changing role of circumpolar boreal forests and tundra in the global carbon cycle, Water, Air and Soil Pollution, 1993.
91 Keeling 1989, op.cit., p. 198.
92 Bert Bolin, Address to the Ninth Meeting of the Intergovernmental Negotiating Committee for a Framework Convention on Climate Change, Geneva, Switzerland, February 1994.
93 Allan Auclair and Julie Bedford, New perspectives on the terrestrial carbon flux: Importance to the policy debate, ORD EPA Technical Briefing, U.S. Environmental Protection Agency, April 28, 1993.
94 D. Eamus and P.G. Jarvis, The direct effects of increase in the global atmospheric C02 concentration on natural and commercial temperate trees and forests, Advances in Ecological Research, 19:1-55, 1989, p. 24.
95 S.D. Wullschleger, et al., On the potential for a C02 fertilization effect on forest trees - an assessment of 58 controlledexposure studies and estimates of the biotic growth factor, in Woodwell, G.M. (ed.), Biospheric Feedbacks in the Global Climate System: Will the Warming Speed the Warming?, Oxford University Press (in press).
96 Eamus and Jarvis 1989, op. cit., pp. 18-21.
97 Christian Komer and John A. Arnone 111, Responses to elevated carbon dioxide in artificial tropical ecosystems, Science, 257:1672-1675, 1992.
98 Karen M. Clancy, Response of western spruce budworm (Lepidoptera: Tortricidae) to increased nitrogen in artificial diets, Environmental Entomology 21(2)331-344, 1992; D.E.
Lincoln, et al., Response of an insect herbivore to host plants grown in carbon dioxide enriched atmospheres, Oecologia, 69:556-560, 1986.
99 W.M. Havranek and V. Benecke, The influence of soil moisture on water potential, transpiration and photosynthesis of conifer seedlings, Plant and Soil, 49:91-103, 1978.
100 Eamus and Jarvis 1989, op. cit. p. 13.
101 Jerry M. Melillo, et al., Global climate change and terrestial net primary production, Nature, 363:234-240, 1993.
102 Christian Komer, CO,) fertilization: The great uncertainty in future vegetation development, in Vegetation Dynamics and Global Change, 1993, op.cit., pp. 53-70.
103 lbid, p. 63.
104 F. Wayne Bell, Critical Silvics of Conifer Crop Species and Selected Competitive Vegetation in Northwestern Ontario, Forestry Canada, Ontario Region, Great Lakes Forestry Centre, Northwestern Ontario Forest Technology Development Unit, Technical Report 19, 199 1, p. 62.
105 Pekka E. Kauppi, Kari Mielikainen and Kullervo Kuusela, Biomass and the carbon budget of European forests, 1971 to 1990, Science, 256:70-74, 1992.
106 Werner A. Kurz and Michael J. Apps, Contribution of northern forests to the global C cycle: Canada as a case study, Water, Air and Soil Pollution, 1993.
108 Apps et al. 1993, op.cit.
109 Preliminary estimates from the United Nations Food and Agriculture Organization, cited in Allen Hammond (ed.), The 1993 Information Please Environmental Almanac, World Resources Institute, Houghton Mifflin Co., New York, 1992. p. 326.
110 A.M. Gordon, et al., Seasonal patterns of soil respiration and C02 evolution following harvesting in the white spruce forests of interior Alaska, Canadian Journal of Forest Research 17:304-319, 1987.
111 W.A. Kurz et al, The carbon budget of the Canadian forest sector: Phase I, Forestry Canada, Information Report NOR-X-326,1992.
112 Roger D. Hungerford and Ronald E. Babbitt, Overstory removal and residue treatments affect soil surface, air and soil temperature: implications for seedling survival, United States Department of Agriculture, Forest Service, Intermountain Research Station, Research Paper INT 377, 1987.
113 KW. Hearnden, et al., A Report on the Status of Forest Regeneration, Ontario Independent Forest Audit Committee, October 1992.
114 Brian J. Stocks, Global warming and the forest fire business in Canada, in Geoffrey Wall (ed.), Symposium on the Impacts of Climate Change and Variability on the Great Plains, Department of Geography, University of Waterloo, Occasional Paper No. 12, 199 1.
115 Herb Hammond, Seeing the Forest Among the Trees, Polestar, Vancouver, 1991, p. 16.
116 Ibid., p. 29.
117 Ibid., p. 114.
118 Ibid., p. 115.
119 Ibid., p. 116.
120 Apps et al. 1993, op.cit..
121 Ibid., p. 121
122 Thomas M. Smith, Rik Leemans and Herman H. Shugart, Sensitivity of terrestrial carbon storage to C02 -induced climate change: Comparison of four scenarios based on general circulation models, Climatic Change, 21:367-384, 1992.
123 T.M. Smith, J.F. Weishampel, H.H. Shugart and G.B. Bonan, The response of terrestrial C storage to climate change: Modelling C dynamics at varying temporal and spatial scales, Water, Air and Soil Pollution, 64:307-326, 1992, p. 315.
124 L.R. Holdridge, Determination of world plant formations from simple climatic data, Science, 105:367-368, 1947.
125 Thomas M. Smith, Rik Leemans and Harman H. Shugart, Sensistivity of terrestrial carbon storage to C02 -induced climate change: Comparison of four scenarios based on general circulation models, Climatic Change, 21:367-384, 1992. Any transcription errors are the responsibility of Greenpeace.
126 Wolfgang P. Cramer and Rik Leemans, Assessing impacts of climate change on vegetation using climate classification systems, in: Allen M. Solomon and Herman H. Shugart (eds.), Vegetation Dynamics and Global Change, New York, Chapman and Hall, 1993.
127 Allen M. Solomon and Wolfgang Cramer, Biospheric implications of global environmental change, in: Solomon and Shugart, 1993, op cit..
128 Reprinted in James S. Clark, Ecosystem sensitivity to climate change and complex responses, in Richard L. Wyman (ed.), Global Climate Change and Life on Earth, New York, Chapman and Hall, 199 1.
129 Price and Rind 1991, op.cit.
130 Overpeck 1990, op.cit.
131 M.D. Flannigan and C.E. Van Wagner, Canadian Journal of Forest Research, 21(l): 66-72, 1991.
132 B.M. Wotton and M.D. Flannigan, Length of the fire season in a changing climate, Forestry Chronicle, 69(2): 187-192, April 1993.
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143 Shawna L. Naidu, et al., The effects of ultraviolet-B radiation on photosynthesis of different aged needles in fieldgrown loblolly pine, Tree Physiology, 12:151-162, 1993.
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150 IPCC 1990 op. cit.
151 Greenpeace International, Towards a Fossil Free Energy Future - The Next Energy Transition: A Technical Analysis for Greenpeace International, Stockholm Environment Institute - Boston Center, April 1993; The executive summary is available as Fossil Fuels in a Changing Climate: How to Protect the World's Climate by Ending the Use of Coal, Oil and Gas, 1993.
152 For more detailed information on renewable energy technologies,
see Thomas B. Johansson et al., Renewable Energy: Sources for Fuel and
Electricity, Island Press, Washington, D.C., 1993. See also, Greenpeace
International, Power To Change: Case Studies in Energy Efficiency and Renewable