Agriculture intensification and forest fragmentation in the St. Lawrence Valley, Québec, Canada

Abstract

Quantifying remaining forest cover and understanding how thefragmentation process operates with respect to the various land-use practicesare important steps when working to preserve the biodiversity associated withwoodlots in agricultural landscapes. We used LANDSAT satellite imagery, soiltypes, and boundaries of regional county municipalities (RCM) as the samplingunit 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 ofagricultural production on the fragmentation process. On average, 45% of thetotal land area of RCMs is forested. However, in 8 of the 59 RCMs studied 20%orless of the total area is still forest habitat. As agricultural use of landincreased, the density of woodlots also increased but their average sizedecreased. An overall fragmentation effect seems to occur where less than 50%ofthe territory is forested, as it is the case for 31 of the 59 studied RCMs.Fragmentation increased along a gradient from traditional dairyagriculture to more intensive cash crop agriculture. Finally, we foundthat the forest discontinuity index, mean woodlot area, and woodlot densitywerethe best indicators of the ongoing forest fragmentation process, but overallhuman population density is the most useful predictive variable.