Environmental Engineering Reference
In-Depth Information
Figure 24.6
Pathways of energy flow through the marine
ecosystem of Lancaster Sound, Arctic Canada.
Source: Welch et al. (1992).
energy along few food chains. They have low resistance to change. The removal of
vegetation, for example, destroys an insulating cover at the surface which allows heat to
penetrate the soil and melt the permafrost. Once started this is a difficult process to stop,
and usually leads to large thaw lakes. Also the impact of the disturbance will take a long
time to fade. Recovery times are long in the Arctic and hence the ecosystem's resilience
is low.
The large fluctuations in the population size of Arctic land and marine mammals are a
clear sign of young and unstable ecosystems. Charles Elton studied the records of the
Hudson's Bay Company and recognized the eleven-year cycle of the lynx and the
snowshoe hare (Figure 24.7). Arguing that hunting and trapping pressure would not vary
much from year to year, he noted the cyclical nature of the population harvests, with the
predator following the abundance of prey. The four-year population cycle of the lemming
is well known, and it in turn influences the size of the population of arctic foxes,
