A recent study, co-authored by the JRC, finds that planting new hedgerows can provide an efficient, economical and sustainable solution that helps alleviate the isolation of natural habitats, and hence contributes to biodiversity conservation, with minor impacts on agricultural land use.
One of the important aims of conservation plans is to safeguard or increase the connectivity of ecosystems by conserving or restoring the most favourable pathways that exist for the movement of native species between habitat areas.
This study set out to explore whether connectivity between patches of forest would benefit more from the restoration of existing corridors or from the creation of new pathways.
This has important consequences for landscape management.
The focus of the study was on corridors formed by hedgerows across agroecosystems, as fragmentation is particularly severe in agricultural landscapes. This is due to the spread of intensive cultivation, which dramatically decreases the extent of the original forests, reducing them to small fragments scattered in human-dominated lands. In these settings, hedgerows, if they exist, may make the greatest or even the only contribution to connectivity for many species.
The authors simulated the improvements in connectivity in a real agroecosystem in northern Italy that would be generated for the Hazel Dormouse by 1) restoring existing priority corridors (that already have tree cover, but also have gaps that may be filled through restoration) or 2) by planting hedgerows along new priority pathways that currently have no tree cover.
Implementing new priority pathways by planting hedgerows in strategic locations resulted in substantially larger connectivity gains (+ 38%) than a comparable restoration effort that concentrated on improving corridors that already exist (+ 11%).
The importance of hedgerows
Hedgerows are crucial for the long-term survival of different species, acting both as corridors and as additional reproductive habitat. As they only occupy a small amount of productive crop areas, they are an ideal target for management actions designed to increase connectivity for animal species in heterogeneous landscapes.
The plantation of new hedgerows in the agroecosystems of the European Union is also encouraged by the Common Agricultural Policy (CAP) and the Rural Development Regulation.
The optimum habitats for the Hazel Dormouse are broadleaved forests with a well-developed shrub layer that can provide routes through branches, suitable nesting sites and shelter from predators. In highly modified lowland areas of Italy, where broadleaved forests are fragmented in small residual patches, the survival of the Hazel Dormouse also depends on well-structured networks of hedgerows, which facilitate movement and provide suitable habitats for the species.
In the area of the study, hedgerows have an average width of about 7 m and an average length of about 150 m, and consist of both residuals of native woodlands and new plantations, typically with trees such as oaks, poplars, alders and willows, accompanied by a more or less developed shrub layer.
Implications for landscape management
The authors demonstrated the benefits of using analytical procedures to compare the effectiveness of different management strategies for enhancing connectivity.
The approach proposed in the study, from the simulation of management strategy implementation to the final maps of priority actions, could have important implications concerning the conservation of species that are sensitive to fragmentation in highly modified agroecosystems.
It may also be applied to other species that are sensitive to fragmentation in other geographical contexts, and for which habitat connectivity may be an important concern for their conservation in highly modified landscapes.
- 31 august 2018