Mountains are highly diverse in areal extent, geological and climatic context, ecosystems and human activity. As such, mountain environments worldwide are particularly sensitive to the effects of anthropogenic climate change (global warming) as a result of their unique heat balance properties and the presence of climatically-sensitive snow, ice, permafrost and ecosystems. Consequently, mountain systems-in particular cryospheric ones-are currently undergoing unprecedented changes in the Anthropocene. This study identifies and discusses four of the major properties of mountains upon which anthropogenic climate change can impact, and indeed is already doing so. These properties are: the changing mountain cryosphere of glaciers and permafrost; mountain hazards and risk; mountain ecosystems and their services; and mountain communities and infrastructure. It is notable that changes in these different mountain properties do not follow a predictable trajectory of evolution in response to anthropogenic climate change. This demonstrates that different elements of mountain systems exhibit different sensitivities to forcing. The interconnections between these different properties highlight that mountains should be considered as integrated biophysical systems, of which human activity is part. Interrelationships between these mountain properties are discussed through a model of mountain socio-biophysical systems, which provides a framework for examining climate impacts and vulnerabilities. Managing the risks associated with ongoing climate change in mountains requires an integrated approach to climate change impacts monitoring and management.

The Canadian Arctic is characterized by a high variation in landform types and there are complex interactions between land, water and the atmosphere which dramatically affect the distribution of biota. Biodiversity depends upon the intensity, predictability and scale of these interactions. Observations, as well as predictions of large-scale climate models which include ocean circulation, reveal an anomalous cooling of northeastern Canada in recent decades, in contrast to the overall significant increase in average annual temperature in the Northern Hemisphere. Predictions from models are necessary to forecast the change in the treeline in the 21st century which may lead to a major loss of tundra. The rate of change in vegetation in response to climate change is poorly understood. The treeline in central Canada, for example, is showing infilling with trees, and in some locations, northerly movement of the boundary. The presence of sea ice in Hudson Bay and other coastal areas is a major factor affecting interactions between the marine and terrestrial ecosystems. Loss of ice and therefore hunting of seals by polar bears will reduce bear and arctic fox populations within the region. in turn, this is likely to have significant effects on their herbivorous prey populations and forage plants, Further, the undersurface of sea ice is a major site for the growth of algae and marine invertebrates which in turn act as food for the marine food web. A rise in sea-level may flood coastal saltmarsh communities leading to changes in plant assemblages and a decline in foraging by geese and other consumers. The anomalous cooling in the eastern Arctic, primarily in late winter and early spring, has interrupted northern migration of breeding populations of geese and ducks and led to increased damage to vegetation in southern arctic saltmarshes as a result of foraging. It is likely that there has been a significant loss of invertebrates in those areas where the vegetation has been destroyed, Warming will have major effects on permafrost distribution and on ground-ice resulting in a major destabilization of slopes and slumping of soil, and disruption of tundra plant communities. Disruption of peat and moss surfaces lead to loss of insulation, an increase in active-layer depth and changes in drainage and plant assemblages. Increases of UV-B radiation will strongly affect vulnerable populations of both plants and animals, The indigenous peoples will face major changes in life style, edibility of food and health standards, if there is a significant warming trend. The great need is for information which is sensitive to the changes and will assist in developing an understanding of the complex interactions of the arctic biota, human populations and the physical environment.