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Habitat defragmentation measures for infrastructure, 2014

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On 1 January 2015, about 41% of the 215 barriers in the Dutch National Ecological Network caused by national transport infrastructure had been completely eliminated by taking mitigation measures, such as the construction of wildlife passages. In the period to 2014 a total of more than 1700 wildlife crossings were constructed on motorways and provincial roads.

The multi-year habitat defragmentation programme (MJPO)

In 1974 the then Ministry of Transport, Public Works and Water Management started building badger tunnels under motorways. In 1988 two large green bridges were built over the A50 motorway in the Veluwe region. By 2005 about 440 wildlife crossings had been built on motorways.

The multi-year habitat defragmentation programme (Meerjarenprogramma Ontsnippering, MJPO), introduced in 2005, aims to remove the barrier effects of major roads, waterways and railways in the National Ecological Network. ProRail and Rijkswaterstaat are responsible for implementing the programme, which they do in close cooperation with the provincial authorities. The MJPO identifies 215 barriers caused by national transport infrastructure. The target of the programme is to eliminate these obstacles by 2018 at the latest. Efforts to eliminate them involve measures like green bridges, wildlife underpasses, eco-culverts, wildlife overpasses at tree crown level and hop-overs. In many cases, existing bridges and viaducts are evaluated for opportunities to make them suitable as wildlife overpasses. The use of wildlife fencing or guiding animal movements by hedges or ridges with tree stumps is a tried and tested approach. However, some barriers may require the construction of several wildlife crossings because they stretch across several kilometres or consists of multiple obstacles.

Less than half of all barriers completely eliminated

By the end of 2014, 41% of the obstacles had been eliminated, while 27% had been partially eliminated. In this context, 'eliminated' means that measures have been taken to address these obstacles. A monitoring programme will be needed to assess whether these measures are working as intended and have eliminated the barriers posed by the infrastructure. According to the programme of works adopted in 2014, by the end of 2018 when the MJPO programme ends, 159 barriers will have been eliminated and 29 partially eliminated, which means that 85% of the programme will have been completed. Since 2005 some wildlife crossings not included in the MJPO have been built on motorways. Most of these are on new road construction projects. Smaller wildlife passages have also been built by municipal councils and nature conservation organisations to remove local barriers. As there is no national record of these wildlife passages, they are not included in this indicator. The indicator does include the 1100 or so wildlife crossings on provincial roads.

Why take measures to mitigate habitat fragmentation?

In smaller isolated habitat patches where the exchange of individuals with other areas is restricted or impossible, populations of plants and animals may become too small to remain viable because the area of habitat is insufficient. The chance of extinction in these areas increases if food is in short supply, for example because of extreme weather conditions. If a species disappears from such an isolated area of habitat, it will not be able to recolonise it when conditions become favourable again. Many species are on the Red List because the habitats on which they depend have become too small and/or isolated. In the Netherlands habitat fragmentation is often caused by roads. Besides the roads themselves, cattle grids and noise barriers can also present unsurmountable barriers. Species such as badgers, foxes, deer, frogs and even some birds, bats and insects have great difficulty in crossing roads, or may be unable to do so at all, which prevents them from moving through the landscape. Patches of species habitats can become isolated as a result. Even if individual animals are physically capable of crossing a barrier, they may be killed by vehicles or avoid the road altogether and alter how they use their habitat. The barrier effect of roads therefore inhibits exchange between animal populations.

The construction of wildlife crossings allows animals to move between areas of habitat. When there is sufficient exchange of individuals between habitat patches, a species will have a greater chance of survival. For species to survive over the long term, therefore, it is essential that individuals are able to disperse and move between habitat patches. Climate change makes it even more important for individuals of a species to be able to move between different areas.

Use and effectiveness of wildlife crossings

Surveys show that most wildlife crossings are used by several species. It has now been demonstrated that wildlife crossings - in combination with wildlife fencing - can considerably reduce road mortality. These crossings have also allowed some species to expand their range or recolonise areas of habitat. It is not known exactly what effect wildlife crossings have on the viability of animal populations, but model calculations show that in many places wildlife crossing are essential for the long-term survival of some species populations. At the moment, though, few studies have been done that demonstrate this in the field as well.

National Ecological Network policy

The Dutch National Ecological Network (NEN) was introduced in the 1990 Nature Policy Plan by the then Ministry of Agriculture, Nature and Food Quality. The aim of the NEN is to halt the decline in the area of natural habitat and biodiversity(1) through the creation of a coherent network of protected areas. This is being achieved by increasing the size of natural areas(2) and connecting them by creating wildlife crossings(3) so that more species can find suitable habitats and the long-term viability of many species populations can be ensured(4). Large areas of natural habitat also help to restore natural water tables and improve water quality and environmental conditions(5). Areas of natural habitat are increased in size and linked together by acquiring land and carrying out landscape works, and through appropriate management of surrounding land and agricultural enclaves (6). In 2013 an agreement was made between national government and the provincial authorities on nature policy and the realisation of the NEN. Although responsibility for the creation and management of the NEN has been delegated to the provinces, it is still a fundamental element in the government's vision on nature.

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Reference for this page

CBS, PBL, RIVM, WUR (2016). Habitat defragmentation measures for infrastructure, 2014 (indicator 2051, version 09 , 29 March 2016 ). www.environmentaldata.nl. Statistics Netherlands (CBS), The Hague; PBL Netherlands Environmental Assessment Agency, The Hague; RIVM National Institute for Public Health and the Environment, Bilthoven; and Wageningen University and Research, Wageningen.

The Environmental Data Compendium is a partnership of CBS, PBL, RIVM and WUR.