Maritime Antarctic climate change: signals from terrestrial biology
The simplicity of maritime Antarctic terrestrial ecosystems, combined with rapid changes in several environmental variables, creates a natural laboratory probably unparalleled worldwide in which to study biological consequences of climate change. The Antarctic Peninsula and Scotia Arc provide a gradient from oceanic cool temperate to frigid continental desert conditions, giving a natural model of climate change predictions. Biota are limited by the twin environmental factors of low temperature and lack of water, while also facing changes in the timing of UV-B maxima, associated with the spring ozone hole. Biological changes consistent with predictions from climate amelioration are visible in the form of expansions in range and local population numbers amongst elements of the flora. Field manipulations demonstrate (i) potential for massive species and community responses to climate amelioration, (ii) the importance of existing soil propagule banks, and (iii) biochemical responses to changing radiation environments. Antarctic species possess considerable resistance/resilience and response flexibility to a range of environmental stresses. Wide environmental variability in Antarctic terrestrial habitats also means that predicted levels of change often fall well within the range already experienced. Thus, climate amelioration may generate positive responses from resident biota, at least while they remain protected through isolation from colonization by more effective competitors. Responses are likely to be subtle and multifactorial in origin, arising from changes in resource allocation and energy economics. The integration of subtle responses may lead to greater consequential impacts in communities and ecosystems.