Agriculture intensification and forest fragmentation in the St. Lawrence valley, Quebec, Canada

Quantifying remaining forest cover and understanding how the fragmentation process operates with respect to the various land- use practices are important steps when working to preserve the biodiversity associated with woodlots in agricultural landscapes. We used LANDSAT satellite imagery, soil types, and boundaries of regional county municipalities (RCM) as the sampling unit of a 6 million- ha territory located in southern Quebec (Canada), to provide a picture of the forest situation in the St. Lawrence Valley. We assessed the effect of human population densities and various types of agricultural production on the fragmentation process. On average, 45% of the total land area of RCMs is forested. However, in 8 of the 59 RCMs studied 20% or less of the total area is still forest habitat. As agricultural use of land increased, the density of woodlots also increased but their average size decreased. An overall fragmentation effect seems to occur where less than 50% of the territory is forested, as it is the case for 31 of the 59 studied RCMs. Fragmentation increased along a gradient from traditional dairy agriculture to more intensive cash crop agriculture. Finally, we found that the forest discontinuity index, mean woodlot area, and woodlot density were the best indicators of the ongoing forest fragmentation process, but overall human population density is the most useful predictive variable.