This is Chapter 7 of the Arctic Climate Impact Assessment
Lead Author: Terry V. Callaghan; Contributing Authors: Lars Olof Björn, F. Stuart Chapin III,Yuri Chernov,Torben R. Christensen, Brian Huntley, Rolf Ims, Margareta Johansson, Dyanna Jolly Riedlinger, Sven Jonasson, Nadya Matveyeva,Walter Oechel, Nicolai Panikov, Gus Shaver; Consulting Authors: Josef Elster, Heikki Henttonen, Ingibjörg S. Jónsdóttir, Kari Laine, Sibyll Schaphoff, Stephen Sitch, Erja Taulavuori, Kari Taulavuori, Christoph Zöckler
The dominant response of current arctic species to climate change, as in the past, is very likely to be relocation rather than adaptation. Relocation possibilities vary according to region and geographic barriers. Some changes are occurring now.
Some groups such as mosses, lichens, and some herbivores and their predators are at risk in some areas, but productivity and number of species is very likely to increase. Biodiversity is more at risk in some ACIA regions than in others: Beringia (Region 3) has a higher number of threatened plant and animal species than any other ACIA region.
Changes in populations are triggered by trends and extreme events, particularly winter processes.
Forest is very likely to replace a significant proportion of the tundra and this will have a great effect on the composition of species. However, there are environmental and sociological processes that are very likely to prevent forest from advancing in some locations.
Displacement of tundra by forest will lead to a decrease in albedo, which will increase the positive feedback to the climate system. This positive feedback is likely to dominate over the negative feedback of increased carbon sequestration. Forest development is very likely to also ameliorate local climate, for example, by increasing temperature.
Warming and drying of tundra soils in parts of Alaska have already changed the carbon status of this area from sink to source. Although other areas still maintain their sink status, the number of source areas currently exceeds the number of sink areas. However, geographic representation of research sites is currently small. Future warming of tundra soils is likely to lead to a pulse of trace gases into the atmosphere, particularly from disturbed areas and areas that are drying. It is not known if the circumpolar tundra will be a carbon source or sink in the long term, but current models suggest that the tundra is likely to become a weak sink for carbon because of the northward movement of vegetation zones that are more productive than those they displace. Uncertainties are high.
Rapid climate change that exceeds the ability of species to relocate is very likely to lead to increased incidence of fires, disease, and pest outbreaks.
Enhanced carbon dioxide concentrations and ultraviolet-B radiation levels affect plant tissue chemistry and thereby have subtle but long-term impacts on ecosystem processes that reduce nutrient cycling and have the potential to decrease productivity and increase or decrease herbivory.
Chapter 7: Arctic Tundra and Polar Desert Ecosystems
7.2 Late-Quaternary changes in arctic terrestrial ecosystems, climate, and ultraviolet radiation levels
7.3 Species responses to changes in climate and ultraviolet-B radiation in the Arctic
7.3.1 Implications of current species distributions for future biotic change
7.3.2 General characteristics of arctic species and their adaptations in the context of changes in climate and ultraviolet-B radiation levels
7.3.3 Phenotypic responses of arctic species to changes in climate and ultraviolet-B radiation
7.3.4 Genetic responses of arctic species to changes in climate and ultraviolet-B radiation levels
7.3.5 Recent and projected changes in arctic species distributions and potential ranges
7.4 Effects of changes in climate and UV radiation levels on structure and function of arctic ecosystems in the short and long term
7.4.1 Ecosystem structure
7.4.2 Ecosystem function
7.5 Effects of climate change on landscape and regional processes and feedbacks to the climate system
7.6 Synthesis: Scenarios of projected changes in the four ACIA regions for 2020, 2050, and 2080
7.7 Uncertainties and recommendations
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