Jean Pennycook (Penguin Science)
Life in Warming Polar Regions
Worldwide, climate change is causing changes in ecosystems. Scientists have found that events like leaf-unfolding, bird migrations, and egg laying are happening earlier each spring. They have also found that plants and animals have shifted in range towards the Poles as climate has warmed. In the future, the ability of many ecosystems to absorb changes is likely to be exceeded as the Earth continues to warm. Ecosystems will also be endangered by other types of global changes such as changes in land use, pollution, and overuse of resources. This may change the way species interact in ecosystems, change the geographic ranges of species, and lead to the extinction of more than 20 percent (one out of five) of plant and animal species.
Ecosystems of the polar regions are no exception; both Arctic and Antarctic ecosystems have changed as climate has warmed. The Arctic ecosystems are changing very rapidly. Predictions for the future anticipate even more changes, according to the fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC). A few of the changes to Arctic and Antarctic life that have been observed are described below.
Arctic
The Arctic tundra ecosystem is changing as the Arctic warms. Over the past 20 years the amount of Arctic tundra has decreased by approximately 18 percent according to comparison of satellite imagery calibrated with surface measurements. As the tundra has warmed, some areas have become home to shrubs, species than were previously unable to grow in the harsh environment. Other areas of tundra have been converted to wetlands as the frozen soils (permafrost) have thawed.
Bird species that are not commonly found in the tundra are now starting to migrate there. Their geographic range, the climate that they can survive within, is shifting northward and so the birds are moving too. Other birds that are commonly found in the arctic are not able to find the environmental conditions they need. For example, the Black Guillemot colony on Cooper Island on the Arctic coast of Alaska is having trouble keeping chicks alive because their food supply, arctic cod, has become limited because the sea ice now melts earlier in the spring reducing the number of Arctic cod. Marine mammals, which also consume fish, may also have been affected by climate shifts. Polar bears, which rely on sea ice as a platform to hunt for seals and other marine life, are also declining as the sea ice melts.
Antarctic
Warmer temperatures mean that there is less sea ice in the Southern Ocean. Krill, a shrimp-like animal that is the favorite food of several penguin species, live under sea ice. Without the ice, there is less krill. And without the krill, there is less food for penguins like the Adelie and Emperor.
Adelie penguins were once quite common on the Antarctic Peninsula. Now most Adelie colonies in the area have been abandoned. Warming of the Antarctic is anticipated to happen much more slowly than the Arctic because the large cold continent of Antarctica covers the Pole. However, the Antarctic Peninsula, the northernmost part of Antarctica, has been warming very rapidly in recent decades – so there is less sea ice under which Adelie penguins look for food. The warmer temperatures appear to be favorable for other penguin species. The Gentoo and Chinstrap penguins have expanded their range into the area of the Antarctic Peninsula where the Adelie used to be able to live. Elsewhere on Antarctica, where the effect of warming is still negligible, the Adelie penguins continue to live. Scientists continue to study the Adelie penguins to better understand how they will be affected by future global warming.
Like Adelie penguins, Emperor penguins also rely on sea ice. They need the ice, not only as a place to find food, but also for nesting sites. Emperor penguins raise their chicks on sea ice. If warmer temperatures cause the ice to melt earlier in the spring, before the chicks are large enough to swim, the chicks will drown. Over the past 50 years, the number of Emperor penguins has dropped by half.
