Human-modified habitats in the Arctic
This is Section 10.2.5 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
The concept of the Arctic as a pristine environment is a widespread fallacy. Humans have long been involved in the Arctic, both directly and indirectly, with little effect on its biodiversity, although hunting and gathering activities, and grazing of domesticated stock, must have had some effect. Damming of rivers to create fish traps is one of the few examples of early intensive environmental modification by people, as is the effects of over-grazing in Iceland. It is only since about 1800 that people have had significant impacts on arctic biodiversity through intensive intentional, or unintentional, modification of terrestrial, freshwater, or marine environments. The main environmental modifications have been through:
expansion of marine and, to a lesser extent, freshwater commercial fisheries, especially with the advent of recent technologies;
aquaculture as an emerging marine industry; and
industrial, urban, and recreational developments, which have expanded considerably in recent decades, resulting in modifications to most types of habitat, regional production and dispersal of contaminants, and associated expansion of communication networks.
The actual proportions of terrestrial, freshwater, and marine habitats that are directly managed for human use in the Arctic are still very small, in contrast with the situation in other areas of the world (except the Antarctic), where agricultural habitats growing crop plants abound, and where derelict land, left over from activities such as mining, quarrying, or municipal development, is not uncommon. Agriculture within the Arctic is very limited; forestry is slightly more frequent. Around settlements and industrial developments there have been substantial changes to the natural environment, and non-native (weed) species have been able to establish in these disturbed habitats. However, the projected changes in climate are very likely to result in significant expansion and intensification of these human activities across the region, particularly where climate warming is most marked. The greatest potential impacts on biodiversity are likely to be through fragmentation of terrestrial ecosystems and the expansion of marine traffic as sea-ice conditions become less severe in the Northeast and Northwest Passages. There are at least four fundamental characteristics of arctic biodiversity that make it sensitive to these developments.
Many arctic plants and animals have slow growth rates and are long-lived as adaptations to the short summer season. These characteristics limit their capacity to respond to relatively rapid changes in their environment, especially when these recur over relatively short time periods. Recurrent disturbance tends to select for species with ruderal characteristics, some of which are found in species living in sites where freeze–thaw cycles predominate.
The low productivity of most habitats forces fauna to forage or hunt over large areas. Finding suitable habitats for breeding and shelter further extends the range requirements. Thus fragmentation of habitats and limitations to movement could potentially affect many species.
The flora and fauna have been selected to survive under extreme climatic conditions. This has given them a competitive advantage in the Arctic over species from warmer climates. Climate warming is very likely to result in a gradual northward shift in arctic species as a result of a natural northward shift in the ranges of more southerly species. However, the projected increase in human activities will also result in the introduction of non-native species, some of which are expected to compete successfully with the native species. This is analogous to the experience of species introductions on isolated islands.
Some species that breed in the Arctic migrate to lower latitudes to avoid the extreme winter conditions. Migration places significant energetic stress on the animals; this means that the animals have evolved specific routes which provide access to transit feeding areas. The modification of habitats by people, both within and outside the Arctic, can have significant impacts on particular migratory species or populations.
These four characteristics of the flora and fauna of the Arctic make them particularly sensitive to the expansion of human activities in the region. For example, the effects of over-grazing by domestic livestock are clearly evident in Iceland where the vegetation cover has been lost and soil erosion is severe. This has led to desertification, with more than 50% of Iceland’s land area (excluding that under permanent ice) being classified as either in "poor condition" or "bad condition". The history of desertification in Iceland was outlined by Arnalds, and stands as a reminder of what can happen when the land’s vegetative cover is damaged. The vegetation in other areas of the Arctic has evolved in the presence of large herbivorous mammals, unlike Iceland’s vegetation, a factor which was thought by Arnalds to be significant.
Climate change is likely to cause gradual expansion at the northern boundary and contraction at the southern boundary of the range of arctic species. In contrast, the expansion of human activities in response to climate change is very likely to cause more rapid northward movement and the introduction of non-native species. The latter will occur mainly through accidental transport and release of individual organisms and propagules beyond their current, natural distribution limits. Such introductions, although having a very low probability of survival (the 10%:10% rule, resulting in only 1% becoming problematic), will occasionally result in the establishment of populations that expand rapidly, causing invasions which are highly predictable in general but highly unpredictable in detail. Thus, a key lesson is "to expect the unexpected".
Conservation action needs to both prevent serious loss of biodiversity and hence ecosystem function, and to restore past damage. The work of the Soil Conservation Service in Iceland demonstrates the difficulty of restoring grossly damaged ecosystems, how long the process is likely to take, and the potential problems that can be caused by non-native, invasive species. In a changing environment it is also necessary to recognize that a few of the wild relatives of cultivated plants occur in the Arctic. Being on the northern edge of their ranges, these might have particular genetic traits that prove valuable in breeding new varieties of crop plants for use under different climatic conditions.
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
- ^Arnalds, O., E. F. þorarinsdottir, S. Metusalemsson, A. Jonsson, E. Gretarsson and A. Arnason, 2001. Soil Erosion in Iceland. Iceland Soil Conservation Service, Hella.
- ^Arnalds, O., 2000. Desertification: an appeal for a broader perspective. In: O. Arnalds and S. Archer (eds.). Rangeland Desertification, pp. 5–15. Kluwer Academic Press.
- ^Williamson, M., 1996. Biological Invasions. Chapman and Hall.
- ^Heywood, V. H. and D. Zohary, 1995. A catalogue of the wild relatives of cultivated plants native to Europe. Flora Mediterranea, 5:375–415.