The role of agricultural ditch banks as corridors

In Europe, strategies such as planned nature reserves coupled with agri-environment schemes (AES) are intended to maintain biodiversity in agricultural areas where plant species in particular are often reduced in number by intensive farming.  One AES method to maintain biodiversity over the long term is to manage ditch banks around the farmland as corridors, allowing plant species to disperse and populate the landscape.  Nature reserves have the potential to act as species-rich sources for these ditch bank corridors.  In their recent paper in Biological Conservation, van Dijk et al. examine whether nature reserves can in fact act as source populations, whether ditch banks can act as effective corridors to support biodiversity, and whether a species’ dispersal ability impacts its ability to take advantage of ditch banks as corridors.

Using data collected by local farmers over a 10 year time period in the Netherlands, the authors found that plant species richness increased slightly over time in ditch banks under AES, mostly from water-dispersed species. The use of ditch banks as corridors was supported by the clear decline in ditch bank richness with an increasing distance to nature reserves. However, this spatial decline of richness flattened out over the 10 year period. This suggests that over this period plants have increasingly established themselves at greater distances from nature reserves. This finding supports the use of ditch banks as corridors and nature reserves as source populations, with water-dispersed species benefiting the most from the configuration.  Although dispersal may be slow, management of ditch banks that allows for easier dispersal of a wide variety of species would more effectively link the landscape in an increasingly agricultural area.