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Railway Embankments as New Habitat for Pollinators

29 August 2014

Great effort has been applied to the development of protection plans in order to sustain the current level of ecosystem services provided by pollinators. Interventions in agriculture, i.e. agri-environmental schemes or the creation of nature reserves in semi-natural habitats, have been devised in the hope that many pollinator populations will survive

Pollinators play key roles in the ecosystem services essential for maintaining wild plant diversity and agricultural productivity. In the temperate zone the main pollinator groups are bees, butterflies and hoverflies.

Many plant species directly dependent on insect pollination for fruit and seed production may experience pollination limitation if pollinator species are scarce. Therefore, evidence of declines of some native pollinator populations reported throughout Europe and North America are of wide environmental and economical concern.

The main factor causing declines of pollinator diversity and abundance is intensification of agriculture. In farmland, the decrease of pollinators' food base and nesting resources are triggered by habitat loss. However, also the cessation of management practices may negatively affects resources needed by pollinators via natural succession (encroachment of shrubs and trees) and invasion of non-native plants.

Great effort has been applied to the development of protection plans in order to sustain the current level of ecosystem services provided by pollinators. Interventions in agriculture, i.e. agri-environmental schemes or the creation of nature reserves in semi-natural habitats, have been devised in the hope that many pollinator populations will survive.

However, this approach towards the conservation of species diversity faces many practical problems. Agri-environmental schemes generally benefit pollinators, but their effectiveness depends on where they are implemented, what genus or order of pollinators is being targeted or landscape structure.

Reserves are frequently located in areas of marginal value for agricultural production, and thus usually play a minor role as a source of pollinator species for farming. Both the creation of reserves and agri-environmental schemes are costly and hence may be limited to the local scale.

A supplementary or alternative solution for the above-mentioned methods is to take advantage of the unrecognised benefits of man-made habitats for pollinator diversity and abundance. Such novel habitats, usually associated with industrial or infrastructural development, may have high conservation value.

For example, it has been shown that limestone quarries, road verges, former open-surface coal mines, landfills, sandpits, gravel-pits, gardens or urban parks may be refuges for pollinator populations. Thus, habitats created by human activity may significantly mitigate some of the negative results of industry and agriculture.

In the European Union as well as in the United States the overall length of railway lines amounts to more than 200 000 km, and is thus a common feature of the landscape. Moreover, EU members have obligated themselves to develop and promote the railway industry. Accordingly, national program of fast speed rail has been launched in the USA.

Linear elements in the landscape such as railway lines may play an important role for the functioning of biodiversity and ecosystem services. Linear elements may also act as dispersal corridors, reproductive habitats for many organisms but also sink habitats. Although rail lines are frequent elements of many landscapes in the EU and the USA, their contribution to the functioning of biodiversity is not well studied.

It is already recognised that embankments are covered by many flowering plant species. The latter suggests that railway embankments may constitute good habitat for many insect species, including pollinators. Moreover, the specific structure of most railways, i.e. a steep embankment with a dry, insolated area at the top and a wetter area at the bottom, creates a strong environmental gradient that may favour different species and therefore increases overall biodiversity. However, to our knowledge, the value of embankments for pollinators has not been studied.

Therefore, we explored the value of this habitat for major groups of pollinators by comparing richness and abundance of species with those found in typical pollinator habitat in agricultural landscapes: extensively managed or recently abandoned meadows.

We expected that if railway embankments are important then species richness and abundance of pollinators would be similar or higher on embankments than on grasslands. Because railway embankments possess specific features, we also expected that they would be inhabited by different pollinator species than grasslands, adding to overall biodiversity.

Further, we identified environmental factors affecting the richness, abundance and species composition of pollinator species on railway embankments to provide recommendations helpful in the management of this habitat for these insects.

Further Reading

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