ABSTRACT: Effect of human disturbance on the sand dunes at Pinery Provincial Park

CGRG Bibliography of Canadian Geomorphology
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Abstract

Recently formed sand dunes are usually dynamic in nature. They experience a continual flux in sand and their vegetation is likely to change through time. Disturbances such as blowouts are natural phenomena, but disruption of dune building processes may also result from trampling of vegetation. Dunes are particularly susceptible to damage as a result of pressure from recreation. The studies presented in this thesis were carried out on the sand dunes in Pinery Provincial Park, Ontario on the southeastern shore of Lake Huron. The oldest of these dunes are about 400 years in age. However, the study mainly concentrated on those up to 200 years old which are situated nearest to the shore. The historic development of the older dunes to form their parabolic structure was inferred from studies of aerial photographs. Their orientation conformed closely to the dominant onshore winds (those strong enough to cause sand movement). Aerial photographs also showed a significant increase in the number of paths devoid of vegetation since the park was opened in 1957. No evidence was found, however, of an increase in blowouts and alteration of dune structure in the largest dunes which could be attributed to recreational pressure. Transects were set up in disturbed and relatively undisturbed sites to monitor sand movement and vegetation change over a three year period. Large changes in sand level were found only in transects located in campgrounds and picnic areas (disturbed). Change towards sparser and more depauperate vegetation occurred in most vegetated sites. This may, however, be attributed to a dry summer in 1978 rather than recreational pressure. Trampling experiments on established dune vegetation showed that several plant species common on young dunes, such as Arctostophylos uva-ursi and Calamovilfa longifolia, possessed unexpected abilities to recover from a single trampling event. Lichens, on the other hand, were severely affected and showed no recovery at all after one year. Paths across the youngest and smallest dune ridge (about 2-3 m high) have greatly increased as a result of recreational pressure. A preliminary model of the behaviour of blown sand and vegetation at path sites was constructed. Dune topography and vegetation were mapped at path sites and were shown to fit the model closely. Evidence from present studies indicates the potential for severe damage as a result of recreational pressure and strongly suggests a need for management and a careful control of the use of the dunes.

Bibliography of Canadian Geomorphology