Ecological networks, why do we need them?
All organisms need a particular type of place to live in: this is the habitat of the species. For some species this habitat is very large, for others it is rather small, depending on their ecological characteristics and territory size. Western Europe is intensively used by man, with the result that habitats are ‘fragmented’ and sometimes lost. Figure 1 illustrates the process of fragmentation of natural areas. Extensive natural areas (left scheme) are changed over time by human activity such as deforestation. The land surface is decreased, or broken up into small habitat patches (right scheme). |
| Figure 1. The process of fragmentation of natural areas |
Due to the fragmentation of their habitat, many species in Western Europe have already disappeared or may disappear from several regions in the future. As natural areas are fragmented, only small populations of species can survive in the small and isolated habitat patches. Whether species survive or not, often depends on a fragile balance. For example a number of bad years, an epidemic disease or chance may result in the extinction of a species. However, good landscape connectivity will give species a better chance of survival in the long term. Moreover, the impact of climate change, which may result in species and habitats moving north in Europe, may be decreased if landscapes are well connected.
The connectivity of the landscape for a species depends on the mobility of a species and the type of the available habitat and its configuration in the landscape. In this respect corridors are very important for certain species. Together with so-called ‘core areas’ corridors form essential components of ecological networks. An ecological network is a system of areas which are connected via ecological links or physical links. The ecological network usually consists of ‘core areas’ (protected or not), corridors, buffer zones and in some cases nature development or restoration areas. A crucial role in ensuring spatial cohesion of the network is therefore played by corridors.
Currently much effort is put into the development of ecological networks, e.g. by means of the construction of wildlife corridors and road crossings or underpasses.
Corridors in ecological networks
Corridors facilitate biological processes such as dispersal, migration or the regular movement of animals. As such, corridors strengthen the spatial cohesion of the network of habitat patches, which is crucial to the survival of many species.Corridors should be tailor-made
It is important that the individual demands of species are taken into account during the development of corridors. Species differ in their requirements; therefore, corridors have to be tailor-made or species-specific in order to function effectively. However, corridors which are useful to an umbrella species may suit other species with similar requirements, which are typically less demanding than the umbrella species.