Comparaison de l’altération des hydrosystèmes par le castor et la drave dans les parcs nationaux de la Mauricie et de la Jacques-Cartier

Natural parks are areas where the flora and fauna are protected in order to preserve their ecological integrity. The national parks of Canada and Quebec are good examples of such protection. According to Parks Canada, the concept of ecological integrity is defined as a characteristic state of the natural region in terms of its components (physical environment and biological diversity) and the processes associated with them (fire, flood, etc.). In order to implement actions in keeping with ecological integrity, it is important to identify human disturbances and ensure that they imitate, as closely as possible, the natural disturbances and remain within the limits of natural ecosystem variability. The current study was conducted in two parks: the Parc National du Canada de la Mauricie (PNCLM) and the Parc National de la Jacques-Cartier (PNJC), located 130 km west and 60 km north of Quebec City, respectively. In order to determine the extent to which log driving dams (human disturbance) mimic beaver dams (natural disturbance), the effects of beaver dams and of residual log driving dams on wetland and deepwater ecosystems were compared. Existing data on dams and data collected by photo-interpretation were used to map the areas affected by the different dams and to identify the resulting vegetation succession. The results indicate that beaver dams are more numerous than log driving in each park. However, log driving dams generally affect larger areas (> 16 ha) than beaver dams (< 16 ha), suggesting that log drives considerably exceed the area limits of natural ecosystem variability. With regards to the distribution of successional stages of beaver dams and log drives, the results suggest little difference between beaver ponds and log drives; approximately a third of all ponds are water filled, another third are at the stage of wet-prairie marsh and the rest show more advanced stages of degradation (shrub swamp, treed swamp or mesic forest). Although log driving has ceased more than 20 years ago in Quebec, its footprint on hydrosystems is clearly perceptible. Further studies are needed to understand the long term effects of log driving.

Chabot, A. et M. Darveau. 2011. Comparaison de l’altération des hydrosystèmes par le castor et la drave dans les parcs nationaux de la Mauricie et de la Jacques-Cartier. Rapport technique no Q17, Canards Illimités Canada – Québec, Québec. 33 p.

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