Fallow land promotes bird diversity

In recent decades, many of Germany’s animal populations in agricultural landscapes have experienced sharp declines, both in terms of the number of species and the number of individuals. Fallow land is considered an effective measure to slow this decline. Researchers from the University of Göttingen, Thünen Institute of Biodiversity, and the Dachverband Deutscher Avifaunisten (DDA) have investigated the correlation between the proportion of fallow land and the number and abundance of farmland birds over a nine-year study period. The research shows that areas of fallow land can contribute to an increase in the populations of these birds and that the benefits of fallow land depend significantly on the complexity of the surrounding landscape. Their findings were published in the Journal of Applied Ecology.

To find out where areas of fallow land should be most effectively established, the researchers studied fallow land in agricultural landscapes of varying complexity. Complexity was measured by the density of boundary lines between fields, as well as between fields and adjacent woody structures such as hedges or forest edges. Data from the nationwide monitoring of common breeding birds (CBBM) as well as data from agricultural statistics were used for the evaluation.

The results clearly show that establishing areas of fallow land is particularly effective in agricultural landscapes that have a medium level of complexity. The average density of boundary lines in Germany is around 65 metres per hectare of agricultural land. The authors therefore recommend promoting fallow land primarily in these regions with medium structural complexity. "Our research enabled us to identify regions where fallow land should preferably be established in order to have the greatest effect," summarises Dr Sebastian Klimek, Thünen Institute of Biodiversity, who coordinated the study. "In order to stop declining populations of farmland birds nationwide, it is necessary to maintain a minimum proportion of fallow land in the agricultural landscape, adds Professor Johannes Kamp, University of Göttingen and member of the DDA’s advisory board.

The EU's Common Agricultural Policy (CAP) has a strong influence on the total area of fallow land in Germany. Due to changes in the CAP, the amount of fallow land has decreased significantly since the beginning of 2000. The loss of fallow land, especially after the loss of “set-aside” areas in 2007, led to a lack of suitable breeding sites and food for many bird species. Although the "Greening" of the last CAP funding period has slightly increased the total area of fallow land in Germany from 2015 onwards, the country is nowhere near the levels observed before 2007. In the new CAP support period starting in 2023, farms are obliged to set aside 4% of their arable land. This could contribute to an improvement in the population of many farmland birds. In order to restore the pre-2007 level of the farmland bird population, a further increase is required in measures proven to be effective at enhancing biodiversity in the agricultural landscape.

The studies were funded by the Federal Ministry of Food and Agriculture in the project „Monitoring der biologischen Vielfalt in Agrarlandschaften (MonViA)“ (Monitoring Biodiversity in Agricultural Landscapes). The Common Breeding Bird Monitoring is supported by the Federal Agency for Nature Conservation (BfN) with funds from the Federal Environment Ministry and the environment ministries of the Länder.

The studies were funded by the Federal Ministry of Food and Agriculture in the project „Monitoring der biologischen Vielfalt in Agrarlandschaften (MonViA)“ (Monitoring Biodiversity in Agricultural Landscapes). The Common Breeding Bird Monitoring is supported by the Federal Agency for Nature Conservation (BfN) with funds from the Federal Environment Ministry and the environment ministries of the Länder.

Original publication: Hertzog et al (2023) Associations between farmland birds and fallow area at large scales: consistently positive over three periods of the EU Common Agricultural Policy but moderated by landscape complexity. Journal of Applied Ecology. DOI: 10.1111/1365-2664.14400

Contact:

Professor Johannes Kamp

University of Göttingen

Department of Conservation Biology

Bürgerstrasse 50, 37073 Goettingen, Germany

Email: johannes.kamp@uni-goettingen.de

Tel:+49 (0)551-39 25207

www.uni-goettingen.de/en/646507.html

Dr Sebastian Klimek                                                      

Thünen Institute of Biodiversity

38116 Braunschweig, Germany                                     

Email: sebastian.klimek@thuenen.de                             

Tel: +49 (0)531 596-2540                                               

www.thuenen.de/en/institutes/biodiversity/staff/klimek-sebastian