COS 72-9
Implications of hedgerow networks for structural connectivity and farmland allocation in Delta, British Columbia
In the estuaries of Delta, British Columbia, key biodiversity hotspots intersect with some of the province’s most productive agricultural land. In light of the loss of natural ecosystems on farmland, governmental bodies advocate for the use of best management practices which protect perennial land cover for biodiversity conservation and ecosystem services on farms. Hedgerows have been used in agriculture to fulfill these objectives and have been shown to provide key habitat and travel corridors for local biological communities. Hedgerows have also been used to mitigate dust and pesticide impacts, prevent trespassing as well as provide protection from wind and water erosion. Landscape patterns resulting from hedgerow policies are not well understood in Delta.
This study analyzed the potential landscape-level benefits of hedgerows to perennial land cover and connectivity as well as the trade-off with the amount of farmland needed to expand the hedgerow network in Delta, BC. Baseline hedgerows were defined using a field survey. RapidEye satellite imagery and GIS datasets were used to develop land cover maps. Baseline vegetation was compared to two policy scenarios: expanded hedgerows along roadways and expanded hedgerows along field boundaries. Scenario perennial land covers were compared using landscape metrics (patch size, contiguity and contagion).
Results/Conclusions
Feature extraction methods resulted in an overall 89.9% accuracy for RapidEye land cover classification. Our analysis showed the current baseline for Delta consists of 19% perennial land cover and 71% open cropland. Landscape metrics of habitat quantity and connectivity (patch size, contiguity and contagion) were shown to be an effective means of comparing spatially explicit scenarios. Perennial land cover and connectivity increased as the hedgerow network became finer grain in the roadway and field boundary scenarios. Contagion decreased by 1.2% in the roadway scenario and 5.5% in the field boundary scenario as the distribution of perennial cover increased. The amount of farmland allocated to these setbacks expanded perennial cover by 0.3% in roadway and 1.9% in the field boundary scenario from baseline. However, in the roadway scenario the patch contiguity and the proportionate gain to contagion was higher than field boundary scenarios though roadway patches were smaller.
Spatially explicit scenarios can provide input to farmer incentive programs. These policy scenarios show the potential benefits to some aspects of landscape quality. As other ecosystem services are evaluated for regional hedgerows, these scenarios can provide a basis for estimating compensation amount and the relative value of expanding or conserving hedgerow networks.