Animals as Erosion Agents in the Alpine Zone: Some Data and Observations from Canada, Lesotho, and Tibet

Abstract

Animals can exert a very strong impact on erosion and sediment transport in the alpine. Although the alpine is recognized for its abundance of animals, animal-soil erosion interactions have been poorly studied. Animals exert a direct influence through their burrowing and digging for food and also indirectly by opening the ground to climatic and geomorphic influences, e.g. rain splash, needle ice, and wind erosion. It is this synergy that is important for alpine erosion. Because the alpine zone is subject to freezing, frost action, and snow melt, exposed sediments and/or the availability of drainage through burrows can have a marked effect on sediment transport and slopes. On the steeper, less stable alpine slopes, the effects of loading can cause failure that produces arcuate slip scars, the exposed faces of which can also be exploited by geomorphic processes. In an attempt to study the effect of animals in the alpine zone, measurements of burrowing and digging based on quadrats (5 m × 5 m) along several transects were made in the alpine zone of the Rocky Mountains of Canada. Results indicated an average of 0.0243 m3 25 m−2 sediment displaced due to digging by rodents and a conservative estimation of sediment removal by rodents varying between 600 and 0.6408 m3 km−2 yr−1. Grizzly bears exerted the greatest erosional impact with as much as 0.4958 m3 25 m−2 being measured. Observations (and limited measurements) relating to the impact of animals on the landscape were also obtained from Lesotho and Tibet. These preliminary findings are presented in an attempt to exemplify the various and interrelated effects of animals, climate and geomorphic process for the alpine. It is suggested that significantly more studies are urgently needed as the situation may be exacerbated by climatic warming and/or by the expansion of pastoralism resulting from attempts at sustainable development in developing nations. The impact of animals is an unquantified factor in many development studies, in geomorphic studies in polar or high altitude environments, and in management plans for national parks or the exploitation of natural resources (e.g. through logging).