This blog post is also available in German here.
Dominik Poniatowski and colleagues describe how they evaluated the environmental drivers of species richness and biomass of grasshoppers in grasslands, comparing this between nature reserves and intensively-used agriculture landscape.
Grassland exhibiting low land-use intensity is considered a hotspot of biodiversity in Central Europe. However, particularly since the mid-20th century, grassland land use has often been intensified, or they have been converted to arable land or afforested. As a result, many grassland species have disappeared regionally. One way of preserving the remaining species-rich grasslands is to designate nature reserves. However, the efficiency of such areas is still the subject of controversial debate.
What did we do?
With this large-scale study, covering an area of almost 2,000 km² in Central Europe, we wanted to find out whether the species richness and biomass of grasshoppers in grasslands inside of and outside of nature reserves differ. At the same time, we collected numerous environmental data to analyse the causes of possible differences. Previous studies have not adequately considered this aspect. As a result, we can now clearly identify which measures should be taken to promote species-rich insect communities in grassland.
What did we find out?
Through our study, we can show that significantly fewer grasshopper species occur in intensively used agriculture landscape grasslands (hereinafter termed ‘wider countryside’), and that there is also less grasshopper biomass than in grasslands within nature reserves. There are several reasons for the observed differences.
In the wider countryside, for example, the high land-use intensity has a negative impact on grasshoppers. Almost all sites there are heavily drained, allowing for frequent mowing. Only a few grasshopper species can cope with this. In addition, grasshopper species that require high soil moisture for egg development are usually absent or only occur sporadically in the wider countryside.
Another important factor that influences species numbers is habitat diversity. This is significantly higher in nature reserves than in the wider countryside. In nature reserves, various habitats such as mesic, wet grassland, reed beds, swamps and shrubs can be found in a small area. Nature reserves, therefore, provide a home for numerous species.
What measures would be useful?
Wider countryside
In the intensively-used agricultural landscape, the production of animal feed and food is the top priority. Measures to promote biodiversity can therefore only be implemented here if they are adequately remunerated. Simple, yet very effective measures in mown grassland, include reducing the frequency of mowing and applying less fertilizer. At a regional level, there are already some examples of how the promotion of biodiversity can work in combination with conventional land use. However, such projects have not yet had a widespread effect, as only limited financial resources are available.
Another nature conservation measure to promote species diversity in the normal landscape would be to increase habitat diversity. This can be achieved, for example, by creating or restoring fallows, field margins, fringes and hedges. This would benefit not only grasshoppers, but numerous groups of insects.
Nature reserves
The designation of nature reserves is intended to preserve the flora and fauna found there, and regulations for nature reserves often set priorities. In the study area, for example, the focus is on the protection of meadow birds. Accordingly, farmers are only allowed to mow the grassland after June 15, as the meadow birds have usually finished breeding by this time.
From our point of view, however, the insect fauna could also be promoted with a simple measure. In other parts of Central Europe, for example, the maintenance of unmown strips has proven to be a successful nature conservation measure. Many animals find refuge here after mowing and can recolonize the entire area from there after some time. A small proportion of unmown grassland per site (around 10%) and each mowing event is enough to achieve a noticeable effect for nature conservation. This would also not contradict the aims of meadow bird conservation. On the contrary, insects are an important source of food for many animal species, such as meadow birds.
We also recommend stabilising the water balance by dismantling or blocking drainage systems. However, this is significantly more expensive and more complex to implement than the maintenance of uncut refuges. Against the background of increasingly summer droughts, however, such measures should also be considered.
If we do not succeed in keeping the water in the areas, we will gradually lose the typical species of wet grassland. The scarcity of the Marsh Grasshopper (Pseudochorthippus montanus) and the high frequency of some typical dry grassland species such as the Bow-winged Grasshopper (Chorthippus biguttulus) and the Heath Grasshopper (Chorthippus mollis) make it clear that some sites in the study area are already too dry and that there is an urgent need for action.
Read the full article “Grassland nature reserves safeguard a high species richness and biomass of grasshoppers” in Journal of Applied Ecology.
