Nature, landscape and biodiversity

Habitat defragmentation measures for infrastructure, 2017

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At the end of 2017 114 of the 178 ecological barriers caused by national transport infrastructure had been removed and 46 partly removed by taking mitigation measures, such as the construction of wildlife crossings. As of 2017 there were almost 2,100 wildlife crossings on motorways and provincial roads.

About two-thirds of ecological barriers caused by national transport infrastructure removed

The multi-year habitat defragmentation programme (Meerjarenprogramma Ontsnippering, MJPO; BenW 2004), which was introduced in 2005, aims to remove the ecological barrier effects in the national ecological network (NEN) caused by national transport infrastructure: roads, waterways and railways. Rijkswaterstaat (the government agency responsible for the construction and maintenance of the country's main infrastructure facilities) and ProRail (the rail network operator) are responsible for implementing the MJPO for the national government, under the direction of the provincial authorities. At the end of 2017, of the 178 identified ecological barriers, 114 had been completely removed and 46 partially removed (MJPO 2017). 'Completely removed' means that all the necessary measures have been taken to remove the barrier effect; 'partially removed' means that measures have been taken, but not all the measures that are necessary to completely remove the barrier effect.

Removing these ecological barriers involves building structures such as green bridges, eco-culverts, wildlife underpasses, wildlife overpasses at tree crown level and hop-overs. In many cases it is possible to adapt existing bridges and viaducts to make them suitable for use by wildlife. Tried and tested methods include guiding animals by erecting fences and planting bushes, and introducing rows or low 'walls' of stumps and branches in culverts to provide a suitable micro-environment passageway for small animals. However, some barriers may require the construction of several wildlife crossings because they stretch across several kilometres or consists of multiple obstacles.

Habitat defragmentation measures since the 1970s

Wildlife crossings have been built across motorways and provincial roads since the 1970s. In 1974 the then Ministry of Transport, Public Works and Water Management started building badger tunnels under motorways. In 1988 two large green bridges (overpasses) were built over the A50 motorway in the Veluwe region. By 2005 about 440 wildlife crossing structures had been built on motorways and about 1,100 on provincial roads. Most of the wildlife crossings built since 2005 were incorporated into new road construction projects. At the moment there are 661 wildlife crossings on motorways and more than 1,400 on provincial roads. Smaller wildlife crossing structures have also been built by municipal councils and nature conservation organisations to remove local barrier effects. As there is no national record of wildlife crossings resulting from such local initiatives, they are not included in this indicator.

Revised target adopted in 2015 in view of new NEN boundaries

When the MJPO began there were 215 identified ecological barriers, based on the Targets for the national ecological network. Following a revision of the NEN in 2010 most of the provinces redrew the boundaries of the national ecological network in their territories, the robust ecological corridors were scrapped. In 2015 an assessment was made of the consequences of the revision of nature policy and the reduction in the size of the national ecological network for the MJPO programme and reporting, and the programme was adapted to the new ambitions of the NNN. The remaining barriers in the former robust ecological corridors are no longer included in the current programme. The MJPO is now limited to the barriers in the former robust ecological corridors which were removed before December 2015 and the barriers that have been removed or are due to be removed under the budget provided by the Ministry of Infrastructure and the Environment. The programme now covers 178 barriers.

Achieving the 2018 targets

When the MJPO programme comes to an end in 2018 it is expected that 159 ecological barriers will have been removed. This is 74% of the original target of 215 ecological barriers to be removed and 89% of the revised total of 178 barriers. Of the remaining 19 barriers, 12 will be completely removed and 7 partially removed after 2018 by incorporating the necessary wildlife crossing structures into larger infrastructure projects to be built after the MJPO programme has come to an end.

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, for example, food supply decreases due to 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. 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 of habitat.

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, but cattle grids and noise barriers can also present insurmountable 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. This can result in patches of species habitats becoming isolated. Even if the individuals of a species are physically capable of crossing a barrier, they may be killed by vehicles or avoid the road altogether and adapt their use of the 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 between areas, a species will have a greater chance of survival.

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 crossings 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.

NEN policy objectives

A precondition for the sustainable conservation of biodiversity is spatial connectivity to allow plant and animal species to move between habitat patches. Biodiversity conservation is an important goal of the Convention on Biological Diversity (CBD) as well as the EU Birds and Habitats Directives and the EU Biodiversity Strategy. The Netherlands has made international commitments to meeting the goals of the CBD and the Birds and Habitats Directives (Natura 2000). The Dutch government's national spatial policy is contained in the 2012 National Policy Strategy for Infrastructure and Spatial Planning (Structuurvisie Infrastructuur en Ruimte, SVIR). Spatial connectivity supports the following national interest in the SVIR:

  • National interest 11: Room for a national network of wildlife habitats to aid the survival and development of flora and fauna.

The Dutch national ecological network was introduced in the 1990 Nature Policy Plan by the then Ministry of Agriculture, Nature and Food Quality. The aim of this network is to halt the decline in the area of natural habitat and biodiversity through the creation of a coherent network of protected areas. This is being achieved by increasing the size of natural areas and connecting them by creating wildlife crossings (this indicator) so that more species can find suitable habitats and the long-term viability of many species populations can be ensured (Spatial conditions of the national ecological network, 2021). Large natural areas also help to restore natural water tables and improve water quality and environmental conditions (Environmental quality of surface water and natural area). Areas of natural habitat are increased in size and linked together by acquiring surrounding agricultural land and agricultural enclaves, creating new habitats on this acquired land followed by conservation management (Realisation of the national ecological network - land acquisition and conversion, 1990-2018). In 2013 an agreement (Nature Pact) was made between national government and the provincial authorities on nature policy and the realisation of the national ecological network. Although responsibility for the creation and management of the national ecological network 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 (2018). Habitat defragmentation measures for infrastructure, 2017 (indicator 2051, version 12 , 5 December 2018 ). 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.