Rewilding abandoned landscapes in Europe

For millennia, mankind has shaped landscapes, particularly through agriculture (Figure 1). In Europe, the age-old interaction between humans and ecosystems strongly influenced the cultural heritage. Yet European farmland is now being abandoned, especially in remote areas. The loss of the traditional agricultural landscapes and its consequences for biodiversity and ecosystem services is generating concerns in both the scientific community and the public. Here we ask to what extent farmland abandonment can be considered as an opportunity for rewilding ecosystems. We analyze the perceptions of traditional agriculture in Europe and their influence in land management policies. We argue that, contrary to the common perception, traditional agriculture practices were not environmentally friendly and that the standards of living of rural populations were low. We suggest that current policies to maintain extensive farming landscapes underestimate the human labor needed to sustain these landscapes and the recent and future dynamics of the socio-economic drivers behind abandonment. We examine the potential benefits for ecosystems and people from rewilding. We identify species that could benefit from land abandonment and forest regeneration and the ecosystem services that could be provided such as carbon sequestration and recreation. Finally, we discuss the challenges associated with rewilding, including the need to maintain open areas, the fire risks, and the conflicts between people and wildlife. Despite these challenges, we argue that rewilding should be recognized by policy-makers as one of the possible land management options in Europe, particularly on marginal areas.

Figure 1. Landscape in the Peneda mountain range, Northern Portugal. Over millennia, forests were converted to scrubland, cropland and pastures. With the abandonment of agro-pastoral activities, forest is now expanding from the remnant fragments and megafauna species are increasing.

Reference

Navarro, L.M. and Pereira, H.M. (2012) Rewilding abandoned landscapes in Europe. Ecosystems, 15, 900–912.

Contributed by Prof. Henrique Miguel Pereira

Theoretical Ecology and Biodiversity Change Group, Centro de Biologia Ambiental Faculdade de Ciências da Universidade de Lisboa, Portugal

E-mail address: hpereira@fc.ul.pt

Do fragment size, connectivity and the composition of the landscape surrounding a grassland fragment influence insect species richness?

Calcareous grasslands are among the most species rich habitats in Europe, harbouring an extraordinary diversity of plants and invertebrates (Figure 1). Unfortunately, since the onset of agricultural intensification these grasslands have become increasingly threatened due to conversion to arable land and fertilisation or abandonment and subsequent shrub encroachment. The remaining grasslands are increasingly fragmented and frequently of small size. However, little is known about how the surrounding landscape influences fragmentation effects. In this study we focussed on the interaction between habitat fragmentation and landscape composition on leafhoppers. They are a highly diverse group of herbivorous insects and include many species that are likely to be vulnerable to changes in their environment.

We selected 14 small (0.1–0.6 ha) and 14 large (1.2–8.6 ha) fragments of calcareous grassland in central Germany near the city of Göttingen, differing in isolation from other calcareous grasslands (measured by a connectivity index) and in the composition of the surrounding landscape, i.e. the percentage of arable land surrounding each fragment within a 500 m-radius (ranging from 27 to 77%). Leafhoppers were sampled by sweep netting three times per fragment in summer 2010. The species were subdivided into specialists that depended on calcareous grasslands and generalists that could use the landscape matrix, but most of them still required low-productivity habitats.

Figure 1. An impression of a typical calcareous grassland in the vicinity of Göttingen in July. The leafhopper Batracomorphus irroratus (Cicadellidae, Iassinae) is confined to calcareous grasslands since its host plant Helianthemum nummularium only occurs there. Picture of B. irroratus by Gernot Kunz.

We found that increasing habitat isolation reduced leafhopper species richness in simple (dominated by arable crops), but not in complex landscapes (see Figure 2). Surprisingly, this effect was driven by those species that we had classified as generalists. We assume that in simple landscapes, leafhoppers may find it more difficult to reach the next suitable fragment due to a lack of alternative resources during dispersal and that generalist species use calcareous grasslands as a refuge, since many species depend on low-productivity habitats.  Moreover we found that generalist species richness increased with increasing connectivity on small fragments, whereas it remained stable with increasing connectivity on large fragments. We think that in small, isolated fragments, a higher extinction rate combined with a lower probability of recolonisation may cause the reduced species richness. Finally, we found a steeper increase in generalist species richness with increasing plant species richness on connected than on isolated fragments, assuming that more colonisers reach connected fragments and can subsequently use the available plant resources.

Figure 2. Effect of habitat isolation (measured by a connectivity index) on a) overall leafhopper species richness and b) generalist species richness in conjunction with landscape composition. c) Effect of habitat isolation on generalist leafhopper species richness in conjunction with fragment size. d) Effect of plant species richness on generalist leafhopper species richness in conjunction with habitat isolation (modified from Rösch et al. 2013 - see reference).

Our results are the first to show that insect biodiversity on fragmented calcareous grasslands not only depends on habitat connectivity but that it is interactively affected by the four factors habitat connectivity, landscape composition, habitat area and plant species richness. Isolated fragments that are either small or located in simple landscapes are less likely to receive immigrants after extinction events, leading to a gradual reduction in species richness over time. These patterns should not only apply to leafhoppers but also to other insect groups (e.g. true bugs).

Mitigating the negative effects of habitat fragmentation therefore needs to take the surrounding landscape into account. Management should be prioritised towards increasing the connectivity (i) of small, isolated fragments, (ii) of fragments in simple landscapes and (iii) towards management efforts that enhance dispersal by increasing heterogeneity of both landscape composition and configuration. Moreover, extensive management of fragments by grazing or mowing, both relatively late in the season, to increase habitat quality for leafhoppers would benefit other insect groups as well.

Reference:

Rösch, V., Tscharntke, T., Scherber, C. & Batáry, P. Landscape composition, connectivity and fragment size drive effects of grassland fragmentation on insect communities. Journal of Applied Ecology in press (doi: 10.1111/1365-2664.12056).

Correspondence

Verena Rösch and Péter Batáry, PhD

Agroecology, Department of Crop Sciences

Georg-August University, Göttingen, Germany

verena.roesch@agr.uni-goettingen.de, pbatary@gmail.com

http://www.uni-goettingen.de/en/74726.html

Central-European example for AES set-aside fields, as small pieces of heaven for farmland birds

Farmland biodiversity has collapsed over the last decades in much of Europe, clearly illustrated by the decline of common farmland birds, and attributed mostly to the intensification of land use and farmland management, driven by the demand for more agricultural production. This resulted in serious overproduction in the European Union (EU) in the 1980s. To decrease overproduction, set-aside was introduced, first as voluntary (1988), then as mandatory (1992) agro-economic measure of the Common Agricultural Policy (CAP) of the old member states of the EU (EU15) taking whole fields out of production. By 1993/1994 approximately 6% of all agricultural lands, i.e. around 6.4 million ha, was set-aside in the EU15 countries. Later, a maximum of 10% of arable land was managed annually as set-aside. Several countries introduced volunteer fallowing under agri-environment schemes (AESs) as well, and also in Hungary during the EU accession in 2002.

Although mandatory set-aside fields were established to control production, they were proven to be valuable habitats for farmland birds, derived mostly from the lack of drastic disturbances during management, no arable crop production and any chemical use.

The pressure from the agricultural market and the increased demand for land for bioenergy crop plantations finally led to the abolition of compulsory set-aside in 2008 in the EU. This sudden continent-wide land-use change was predicted to result in wide scale agricultural intensification and supposed to adversely affect farmland biodiversity. Unfortunately, no EU-wide impact assessment or mitigation for set-aside loss was introduced.

However, the abolition of set-asides caused large scale land use change across the EU, the evidence to predict the consequences and develop indicators is geographically restricted, only few evidence of this exists from Central or Eastern Europe. Although these countries have large areas under agricultural management and still harbour valuable ecosystems with rich and dense farmland bird assemblages owned to the current generally more extensive agricultural management. Moreover, the relationship between population declines and agricultural change has been driven by different mechanisms in Central and Eastern Europe, therefore AESs e.g. set-aside management should not be directly extrapolated from Western Europe.

In our study we addressed the question of how could agri-environment scheme set-aside fields be used to mitigate the loss of market regulated fallows to conserve farmland birds. We aimed to assess the effectiveness of set-aside for birds by comparing set-aside and winter cereal fields, and semi-natural grasslands and to examine how bird species richness and abundance change over the course of set-aside age (1-3 years old), related to vegetation changes.

The study sites were located in the Heves Environmentally Sensitive Area (ESA), Eastern Hungary. Creation of set-aside fields is part of the arable farming action plan for the protection of great bustard (Otis tarda). Fields have to be managed by regular crop rotation with set-aside 20–25% of all the farmer’s fields. Fields can be taken out of production for 1–3 years, sown by a three component seed mixture after the last harvest, containing two grass and one leguminous plant species. Vegetation is mown once per year from 15th June.

Six replicates of one, two and three years old set-aside fields were chosen, each with an adjacent winter cereal field pair, and six additional semi-natural grasslands were also assigned. The relative abundance of birds was assessed two times during April and May in 2008.

We proved the effectiveness of set-aside management both in term of higher species richness and abundance of birds compared to the adjacent winter cereal fields. A wide range of insectivorous and granivorous species favoured set-aside fields at a comparable level to semi-natural grasslands. Two and especially three years old set-aside fields seemed to be beneficial also for SPEC (Species of European Conservation Concern) species.

Our study identified the important role of local spatial scale, i.e. vegetation heterogeneity reflects food availability. We found that abundance of several insect taxa increases significantly even in the one-year-old set-aside fields (Kovács-Hostyánszki et al., 2011), however, the high and dense vegetation made at the one-year-old set-aside fields still less suitable for birds. However, in the second and especially in the third year the considerably lower sward height and the mosaic pattern of bare ground patches with increased openness of vegetation resulted in better foraging conditions in the invertebrate rich set-aside fields, resulting in increased species richness and abundance of birds.

We argue that beneficial management of these set-aside fields is crucial for farmland birds, requiring annual mowing to maintain heterogeneous vegetation with patches of both short and taller plants. Besides, the relatively dry Hungarian summers, the high weed seed species pool in the soil and the extensive arable management might result in grasses less likely to dominate the set-aside sward after 2–3 years, which explains their preference over the first year set-asides, compared to Western European examples.

Our findings from a less studied, but diverse region of Europe provide some novel insights into the effects of set-aside management and show a promising way to counteract the negative effects on farmland birds: well-designed AESs have the potential to mitigate the loss of market regulated set-asides.

References:

Kovács-Hostyánszki, A., Báldi A. (2012) Set-aside fields in agri-environment schemes can replace the market-driven abolishment of fallows. Biol. Conserv. 152, 196–203.

Kovács-Hostyánszki, A., Kőrösi, A., Orci, K.M., Batáry, P., Báldi, A. (2011) Set-aside promotes insect and plant diversity in a central European country. Agr. Ecosyst. Environ. 141, 296–301.

Communicated by Kovács-Hostyánszki, Anikó - Centre of Ecological Research, Hungarian Academy of Sciences, Landscape and Restoration Ecology Group. E-mail: kovacsanko@yahoo.co.uk