Dynamics behind Arctic ecosystems revealed

Temperature is decisive

'We have gathered data on all animals and plants characterising the arctic tundra in seven different areas. This has allowed us to generate a picture of how food chains vary over a very large geographical (and, with it, climatic) gradient. Therefore, and for the first time, we can offer an explanation of the factors governing the tundra as an ecosystem,' says Niels Martin Schmidt from Aarhus University, Denmark, one of the researchers behind the study. The researchers have evidenced that temperature is of decisive importance for which elements form part of the food chain, thus permitting them to predict how climate changes may impact whole food chains -- and not just the conditions for the individual species.

The largest avoids being eaten

Temperature regulates which organisms interact with each other in the far north arctic nature. However, the present study also shows that predation, i.e. the interactions between predators and prey, is the factor regulating the energy flows in ecosystems and, with that, the function of the ecosystem.

'Our results show that predators are the most important items of the tundra food chains, except in the High Arctic. The intensity varies with the body size of the herbivores (plant eaters) of the chains. For example, the musk ox is far more likely to avoid being eaten by predatory animals than the lemming,' Niels Martin Schmidt explains.

Researchers have previously revealed similar patterns for the food chains of the African savannas. The researchers behind the present recently published study therefore believe that we may possibly be one step closer to proposing a general principle for how terrestrial ecosystems are structured.

Facts about the project

• Collecting data for the project took place at seven locations in Canada, Greenland, Russia and Norway.
• Nine research nations were involved in the project, which was launched under the title 'The International Polar Year' (2007-2009).
• Based on the data collection, the researchers prepared models of the food net, which show the flow of energy and nutrients.

Facts about the tundra

• The tundra is a habitat found in the far north of North America, Europe and Asia.
• The word tundra comes from the Sami expression tūndar, which means 'flat hill', and the tundra countryside is characterised by shrubs and mosses, rather than large trees.
• The tundra is inhabited by predators that prey on hares and small rodents in particular. Breeding migratory birds visit the tundra in summer, while the bird life is more scarce in winter.