|Dear EarthTalk: How much of a threat does climate change pose to the tundra ecosystems of the far north?|
|— Seamus Hall, via EarthTalk.org|
The tundra biome is among the coldest of the planet’s ecosystems. Its harsh climate means that plant life is unable to grow more than a few centimeters above the ground. The name ‘tundra’ comes from the Finnish word meaning ‘treeless plain’ which is particularly appropriate considering that only low-lying plants dot the landscape.
Much of the ground is frozen “permafrost” made up of dead plant material, gravel and fine sediments. As the global climate warms this permafrost is under threat. Rising global temperatures mean that the abundance of permafrost is decreasing at unprecedented levels. Scientists warn that the planet’s permafrost could disappear completely with only another 1-2 degrees centigrade increase in global temperature. Unless we start curtailing carbon emissions significantly soon, permafrost will likely be a thing of the past as of 2100.
At present the tundra is described as a ‘carbon sink’ which means that it absorbs the world’s carbon and actively lowers the amount of greenhouse gases in the atmosphere. However with the slight increase in world temperatures brought about by climate change it could well become a ‘climate conductor’. This would entail the ecosystem releasing more carbon than it is absorbing. This is because when plant material is frozen solid in permafrost it doesn’t decompose. As a result any carbon that it would have been released during the decomposition process is still locked up in the material. It is estimated that 14 percent of the earth’s carbon is tied up in the permafrost, the release of this amount of carbon would have a profound impact both locally and globally. These rising temperatures mean that material that has been enclosed in the permafrost for many years is thawing out and being able to decompose.
The melting of permafrost through global warming in turn increases the pace that temperatures in the region rise, further exacerbating the issue. The tundra is a vulnerable ecosystem that is made up of sedges and shrubs such as dwarf birch which are adapted to be low growing due to the low temperatures and moisture availability. There is a lack of moisture availability because much of the ground is frozen for the majority of the year. A small increase in temperature has allowed foreign species of both plants and animals to make their way in to the tundra from further south. An example of this occurrence is the Red Fox which has been able to travel further north in to the southern edges of the tundra. The Red Fox is now in direct competition with the Arctic Fox for both food and territory, potentially endangering the long term survival of the Arctic Fox which is only adapted to the unique conditions of the tundra. However the threat posed from increased competition is lessened by the varied diet of the Arctic Fox. It is an omnivore and feeds on lemmings, voles, arctic hares, birds and their eggs. Despite this, two species competing for food that was previous only taken by one can have long term effects to the animals lower down the food chain. Also the migration of the Red Fox is an indication that the Arctic Fox’s territory is decreasing as a result of the tundra being altered by the effects of climate change.
Changes to the biome can have more devastating effects to the region’s current plant species which are adapted to the low moisture availability and harsh conditions. These species may be overrun by invasive species which are able to exist further north due to increasing temperatures and decreasing levels of permafrost. New species would potentially alter the environment of the native species. Species that arrived from warmer, more temperate climates will be more substantial in size and are likely to require more moisture to exist than those adapted to tundra conditions. As a consequence they would likely begin to dominate the landscape at the detriment of native species.
The main threat posed by climate change and specifically global warming to the vulnerable tundra ecosystem is the vast reduction in permafrost levels. It is estimated by more extreme models that 90 percent of the permafrost that existed in 1920 will have disappeared by 2100. As more of the ground thaws it absorbs more light, which speeds up the melting process. Also melting of the permafrost allows foreign plants and animals to migrate into the tundra. This causes greater competition among the native animals and plant species for food, sunlight and territory. As the tundra is close to the North Pole it incurs more extreme temperature rise than the lower latitudes, so if the temperature of the planet rose by an average of one degree centigrade, the north and south poles’ temperature would have risen by a larger amount. This can be particularly devastating because it is the poles which are the most sensitive to changes in climate.