Corridors as a tool for linking habitats – Shortcomings and perspectives for plant conservation

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Habitat fragmentation and isolation are considered important causes of biodiversity loss in cultural landscapes. To counter the negative effects of fragmentation such as reduced connectivity and increased risks of population extinction due to stochastic processes and genetic erosion, it has been proposed to establish linear ecological corridors to facilitate dispersal between isolated habitat patches. We summarise the current knowledge on the potential benefits and limitations of corridors for reducing the negative effects of habitat fragmentation on plant populations. We address the opportunities and problems that are associated with linear corridors and advocate the use of semi-open corridors as an alternative that might overcome some shortcomings of conventional corridors for plants. Observational and experimental studies have found that various types of linear corridors can increase plant dispersal. Other linear structures such as paths, roads, railways and streams may also function to a certain extent as corridors, although mostly for widespread species. Because plants are highly dependent on external agents such as animals or wind to reach new habitats, the effectivity of corridors is strongly influenced by their structural features and suitability for animal dispersers. However, many plant species can only use corridors for long-distance dispersal if they can also use them as stepping stone habitats where they can establish, grow, reproduce and then disperse further. This dispersal critically depends on suitable light conditions and disturbance regimes, and on a sufficient width of a corridor to reduce edge effects. Thus, hedgerows appear to be suitable corridors for some forest species but are too narrow for forest specialists from the interior of woodlands. Corridors do not only have positive effects but may also facilitate the spread of invasive species. Moreover, a potentially underestimated negative effect of linear corridors is that they may actually create new dispersal barriers when they intersect other habitats. For example, linear woodland corridors that intersect grasslands may successfully connect patches of woodland but simultaneously form strong barriers for grassland species and increase the fragmentation of their populations. As an alternative to linear corridors, we recommend “semi-open corridors” that simultaneously connect patches of both open habitats and woodlands and promote the dispersal of species of both types of habitat. This idea is based on the various types of semi-open landscapes in Europe that have been formed by grazing with livestock, resulting in a mosaic of open habitats, groups of trees or shrubs and small woodland patches, and are characterised by a high diversity of environmental conditions on a small scale. Wide corridors of such semi-open habitats may avoid the strong edge and barrier effects associated with linear corridors and provide suitable stepping stone habitats for species with different habitat requirements.

ZeitschriftJournal for Nature Conservation
PublikationsstatusErschienen - 01.04.2021