This is Section 10.2 of the Arctic Climate Impact Assessment
Lead Author: Michael B. Usher; Contributing Authors:Terry V. Callaghan, Grant Gilchrist, Bill Heal, Glenn P. Juday, Harald Loeng, Magdalena A. K. Muir, Pål Prestrud
Earlier chapters focused on the terrestrial, freshwater, and marine environments of the Arctic, and their component species. Several physical characteristics distinguish polar environments from the environments of other regions: limited daylight for much of the year, low temperatures, and low levels of precipitation. Collectively, these limit biological productivity over a large part of the year because photosynthesis and decomposition are severely constrained. In contrast, the brief arctic summer, which experiences continuous daylight and warmer temperatures, generates a large pulse of primary productivity.These dramatic seasonal changes strongly influence the Arctic’s biodiversity. For example, productivity in summer is sufficient to attract migratory species of birds and mammals to the region.
Recent glaciations have resulted in major losses of the resident arctic fauna and recolonization has been slow (particularly in the terrestrial and freshwater environments), owing to both the extreme environmental conditions and the low overall productivity of arctic ecosystems. This has resulted in the arctic ecosystems, in a global sense, being considered “simple”, i.e., having relatively few species.The species that they do contain are mainly “specialists” in the sense that they have been able to adapt to the extreme conditions.Thus, there are few species at any particular trophic level, and overall species diversity in terrestrial, freshwater, and marine habitats is low.
The seasonal constraints result in similar life-history traits in many arctic plant and animal species. Compared to species living in temperate regions, species living in the Arctic throughout the year are typically long-lived, slow-growing, and have low rates of annual reproduction. These factors appear to be adaptive to environments that can vary greatly from year to year, and where productivity is constrained to a short period of time, even in a favorable year. Specifically, these life-history traits are suitable for plant and animal species living in environments where reproductive attempts within a single year may need to be abandoned to ensure adult survival.
Several of these traits may limit the capacity of species to respond to rapid environmental change. High adult survival rates, coupled with low rates of reproduction, make populations slow to recover from catastrophic events. Also, the adaptations unique to species living in polar environments also limit their ability to respond to warming conditions or to the greater environmental variability projected to result from climate change scenarios for the Arctic.
The rest of section 10.2 considers the special features of arctic habitats that make their biological diversity vulnerable to climate change. In their analysis of the European Arctic, Hallanaro and Pylvänäinen recognized nine broad habitat types. Six of these have not been significantly affected by human activities: habitats above and beyond (i.e., north of) the treeline; forests; wetlands; lakes and rivers; coasts and shores; and the sea.The other three have been strongly affected: farmland; urban areas; and mosaic landscapes.
In this chapter the Arctic is considered in terms of five broad habitat groupings, including marine environments; freshwater environments; environments north of the treeline; boreal forests; and habitats intensively modified by people.The term wildlife was defined in Anon as “in a more scientific sense…wildlife refers to all nondomesticated organisms. It includes mammals, birds, fish, amphibians, and reptiles, as well as vascular plants, algae, fungi, bacteria, and all other wild living organisms”. Anon defined habitats as “all the elements of the Earth that are used by wildlife species to sustain themselves throughout their life cycles.This includes the spaces (i.e., terrestrial and aquatic) that they require as well as the properties of those places (e.g., biota, climate, soils, ecological processes and relationships). Habitats function in providing such needs as food, shelter, and a home place. Habitats can be thought of as distinctive places or ecosystems…”.These broad definitions are used in this chapter.
Although it might seem simple to identify terrestrial, freshwater, and marine habitats, as well as the wildlife that occurs in each, in practice it is not because each habitat merges into another. For example, catchments or watersheds on land are terrestrially defined, but water percolating through the soil or running off the soil surface eventually enters streams and rivers. So where do terrestrial habitats end and freshwater habitats begin? Similarly, rivers enter estuaries where they are subject to tides, and species characteristic of rivers meet species characteristic of the sea.Where do freshwater habitats end and marine habitats begin? Along the shore the sea and the land interact, and there may be no clear demarcation between terrestrial and marine habitats.The situation is further complicated by anadromous species, such as Atlantic salmon (Salmo salar).These spawn in rivers, and the young pass through the estuaries on their way to the sea where they mature before returning several years later to their natal rivers to begin the cycle again. The reverse occurs with catadromous species, such as the eel (Anguilla anguilla), which spawns at sea.There are thus gradients, rather than clear boundaries between the wildlife of terrestrial, freshwater, and marine environments, and a pragmatic approach to allocating species and habitats to these broad groupings is taken within sections 10.2.1 to 10.2.4.
Chapter 10: Principles of Conserving the Arctic’s Biodiversity
10.2 Conservation of arctic ecosystems and species
10.2.1 Marine environments
10.2.2 Freshwater environments
10.2.3 Environments north of the treeline
10.2.4 Arctic boreal forest environments
10.2.5 Human-modified habitats
10.2.6 Conservation of arctic species
10.2.7 Incorporating traditional knowledge
10.2.8 Implications for biodiversity conservation
10.3 Human impacts on the biodiversity of the Arctic
10.4 Effects of climate change on the biodiversity of the Arctic
10.5 Managing biodiversity conservation in a changing environment
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