Arctic Biodiversity Trends 2010

21

Indicators at a glance

Arctic Biodiversity Trends 2010

Indicator #13 PAGE 68

Ice cover is an important component of northern freshwater ecosystems, influencing many physical, chemical, and biological processes. The duration of freshwater ice cover has decreased by an average of almost two weeks over the last 150 years, with earlier break-ups and later freeze-ups. As the climate warms, longer open-water conditions will prevail. Depending on the type and location of a water body, decreases in the duration of lake ice can be expected to have a range of ecological impacts from increased productivity and increased habitat availability with less ice to changing distributions and reduced habitat availability for some cold-water species of fish. Effects of decreased freshwater ice cover duration on biodiversity Wetlands cover about 70% of the Arctic with the most extensive wetland types being non-forested and forested peatlands. Peatland species comprise 20–30% of the Arctic and sub-Arctic flora. Arctic peatlands also support biodiversity worldwide through bird migration routes. Seventy-five percent of the more than 60 bird species with conservation priority in the European part of the Arctic are strongly associated with tundra and mire habitats. Peatlands also provide crucial ecosystem services such as habitat maintenance, permafrost protection, and water regulation. Over recent years, the southern limit of permafrost in northern peatlands has retreated by 39 km on average and by as much as 200 km in some parts of Arctic Canada, with some of this attributed to climate change. The northward movement of the treeline will affect not only Arctic biodiversity through shifting habitats and species, but also reduce albedo (surface reflectivity), further enhancing warming of the atmosphere. Indicator #15 PAGE 75 Thermokarst lakes and ponds, formed by the thawing of permafrost, are the most abundant and productive aquatic ecosystems in the Arctic. They are areas of high biodiversity with abundant microbes, benthic communities, aquatic plants, plankton, and birds. While the disappearance and appearance of thermokarst lakes is a relatively common occurrence, there are concerns about their future in the face of climate warming. There has been a net decrease in the number of thermokarst lakes over the past fifty years in the western Canadian Arctic, Siberia, and Alaska. Trends in other Arctic regions are unknown. The appearance and disappearance of thermokarst lakes is projected to be more common with climate change and will likely lead to more aquatic habitat becoming available in higher latitudes over time. The effects of these habitat shifts on local aquatic populations, migratory species, and vegetation is the subject of further investigation. Appearing and disappearing lakes and their impacts on biodiversity Arctic peatlands Indicator #14 PAGE 71