Provision of ecosystem services by large scale corridors and ecological networks
Large scale landscape transformation and contingent habitat loss are among the greatest threats to ecological integrity and ecosystem health. One of the mitigation approaches used to deal with these pressures is to leave interconnected corridors and nodes as remnant ecological networks (ENs) within the transformed landscape. The South African forestry industry has already allocated 500,000 ha, one-third of the plantation holdings, consisting predominantly of natural grassland, as ENs among and within timber plantations. These ENs are intended to maintain structural, compositional and functional biodiversity. However, little scientific research is available on the effectiveness of these huge ENs for biodiversity conservation and maintenance of natural ecosystem function, although initial findings are encouraging. While the local adverse effect of alien plantation trees on functional biodiversity is not in dispute, it is at the scale of the whole landscape where there is much interest in determining how effective these ENs are in maintaining the untransformed portion of the transformed landscape in a close-to-natural state. As these ENs are extensive, species beta diversity is a consideration in addition to alpha diversity. Initial findings reveal diminished ecological integrity in narrow corridors due in part to the adverse edge effect from the alien trees into the margin of the EN. Quality of the ENs is of great importance for maintaining functional diversity, with human disturbance reducing their effectiveness. First findings, and their application to the Framework for Ecosystem Service Provision, suggest that these ENs are significant for biodiversity conservation and for provision of ecosystem services. Nevertheless, still much more research is required on a greater range of taxa, and their interactions, to improve the design of these ENs for ecological and evolutionary processes. © 2009 Springer Science+Business Media B.V.