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Arctic vegetation zones are likely to shift, causing wide-ranging impacts. More...
The main vegetation zones in the Arctic are polar deserts in the north, boreal forests in the south, and a wide expanse of tundra in-between. Polar deserts are characterized by open patches of bare ground and an absence of even the smallest woody shrubs, whereas tundra is characterized by low shrub vegetation.
Climate change is expected to cause the northward expansion of forests into the Arctic tundra, and of tundra into polar deserts. Such changes are likely to take place this century in areas where suitable soils and other conditions exist. This is expected to result in the area of tundra becoming smaller than it has ever been during the past 21 000 years, reducing the breeding area for many birds and the grazing areas for certain land animals.
The total number of species in the Arctic is projected to increase under a warmer climate due to migration of species from the south. Many of the adaptations that enable plants and animals to survive in the Arctic environment also limit their ability to compete with species that move in from the south. Moreover, Arctic species are limited in their northward migration by the Arctic Ocean.
Changes in the ranges of certain bird, fish, and butterfly species have already been observed. At present, there are more varieties of moss and lichens in the Arctic than anywhere else in the world. This type of vegetation is particularly likely to decline as the Arctic warms.
The geographical spread of animals can generally shift much faster than that of plants, and large migratory animals such as caribou can move much more readily than small animals such as lemmings. In addition to mobility, the availability of food sources is another factor that influences the pace at which different species will shift northward. All of these differences will result in the break-up of currently interdependent communities and ecosystems and the formation of new ones, with unknown consequences. More...
4.2.1 The projected northward expansion of boreal forest will cause a decrease in the amount of sunlight reflected by the surface of the Arctic, as the newly forested areas are darker and will absorb more solar radiation than lighter, smoother tundra or bare snow. In this feedback loop warming could thus leads to more tree-cover and, in turn, to still more warming (see also Question 3.1). However, the expanding forest will be denser and grow more quickly than the existing tundra, and the tundra more than the polar deserts it displaces. This could increase the amount of carbon stored within ecosystems, slightly offsetting the projected warming linked to the increased absorption of solar energy.
Total annual precipitation is expected to increase along with temperatures. These changes could, nonetheless, lead to desertification in certain land areas if evaporation increases more rapidly than precipitation. The thawing permafrost could also drain moisture from soils and lead to desertification in some areas if warming continues. More...
4.2.2 Almost one third of the world’s forests are located in Arctic nations, particularly in Siberia and North America. These forests contribute to:
After the last ice age, a warmer period for the Earth’s climate allowed trees to grow much further north than at present. However, whilst current warming seems likely to bring about a similar shift, the actual northern movement of the treeline is highly unpredictable as various factors, including fires, floods and human activities, can influence it. More...
4.2.3 In different areas of the boreal forests, different climatic conditions are favouring or limiting the extent of tree growth. Climate change could, thus, produce two different kinds of response:
Either type of change may allow the formation of ecosystems that are not present in today’s landscape. More...
4.2.4 White spruce is the most widespread boreal conifer, making up most of the forest near the border of the tundra, and a valuable timber resource, especially in North America. This species is highly dependant on climatic conditions and any change could hamper its reproduction by affecting the production of cones and the release of seeds following forest fires. More...
4.2.5 Black spruce is the dominant tree in a large portion of the boreal forest in Alaska. It absorbs a lot of solar energy, thus increasing warming, and it is a highly flammable species that can carry fire across the landscape. The projected warming may affect the survival and geographic spread of the black spruce, as this species can be influenced by changes in permafrost, high temperatures in early spring, and droughts. More...
4.3.1 Large areas of forest are increasingly likely to be disturbed by insect outbreaks linked to warming. Indeed, the warming will create new opportunities for invasive species, such as the Spruce Bark Beetle and the Spruce Budworm, to move in from other regions. More...
4.3.2 Fire is another major disturbance factor in the boreal forest and it has a wide range of ecological effects. The average area of forest burned each year in western North America has doubled over the past thirty years, and it is expected to increase by as much as 80% over the next 100 years. The area of boreal forest burned in Russia averaged four million hectares every year over the last three decades. This area more than doubled in the 1990s. Projected changes in climate would greatly increase the area subjected to the types of weather that cause extreme fire danger. More...
At present, agriculture in the north consists mostly of raising cattle, sheep, goats, pigs, and poultry, herding reindeer, growing cool-season vegetables such as turnips and spinach, and small grains such as rye and oats. In addition to limitations imposed by climatic conditions in the Arctic such as lack of warmth and moisture, and short growing seasons, agriculture is also limited by the lack of infrastructure, a small population base, remoteness from markets, and land ownership issues.
Climate change is expected to increase the range of crops that can be grown in the Arctic. As far north as the Arctic circle, it may soon be possible to cultivate crops that currently only grow in the warmer parts of the arctic region, for instance. Yield increases might actually be constrained by factors such as a rapid but shorter ripening and certain winter conditions. Water deficits are likely to increase over the next century in most parts of the boreal region, because evaporation is likely to increase more rapidly than precipitation as a result of higher temperatures. Irrigation systems will be needed in these areas in order to minimize the effects of water stress on crop yields.
Insects, diseases, and weeds are likely to increase throughout the Arctic with climate warming but, in most cases, their impact is unlikely to offset yield increases or the potential for new crops.
Overall, lack of infrastructure, limited local markets, and long distances to large markets are likely to continue to limit agricultural development in most of the Arctic during this century. More...
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