The good and the bad: the contribution of predators to ecosystem services and disservices
and others (see below)
Agricultural production relies on a multitude of ecosystem services such as soil formation, pollination or biological pest control. Sustainable agro-ecosystems sustain a large number of organisms, such as birds, rodents, bees, beetles or earthworms that support agricultural production. Bees pollinate crops such as oilseed rape, earthworms are crucial for soil formation, whereas birds, rodents and beetles feed on weed seeds and pest insects. By removing structural elements such as hedges, trees or fallows, and due to increasing chemical inputs, modern intensive agricultural production often contributes to the loss of those organisms.
Changes in animal communities mediated by agricultural land-use may reduce the provision of ecosystem services, if beneficial species are negatively affected. In addition, species damaging crops (thus providing so called ecosystem disservices) can become disproportionally abundant in homogeneous agricultural landscapes, or species that are resilient to land-use change may switch from providing services to disservices. To design sustainable crop production systems it is thus crucial to know which organisms provide ecosystem services and which rather contribute to disservices and how the provision of services and disservices is affected by local and landscape conditions.
To investigate the contribution of different animals to ecosystem services and disservices linked to predation, the authors exposed plant seeds and invertebrate prey to predators in cereal fields in southern Sweden. By offering weed seeds and pest prey organisms that can reduce agricultural production, the authors assessed the ecosystem service potential. By simultaneously offering crop seeds and beneficial prey organisms, the authors measured the disservice potential.
The results recently published in Ecological Applications showed that seed predation was dominated by vertebrates, while vertebrates and invertebrates contributed equally to the predation of animal prey. However, there was no obvious difference in each group’s contribution to services and disservices. Predation varied substantially over time, but there was no strong influence of landscape composition on predation numbers. When looking more closely at vertebrate predators recorded by wildlife cameras, another study published in Oecologia showed that rodents were the dominant vertebrate predators for all resources. While rodents were responsible for 90% of all predation by vertebrates, birds only contributed 10%.
Birds, rodents and invertebrate predators provide important ecosystem services such as pest and weed control to farmers. However, depending on the conditions, some may also inflict damage to crops thereby contributing to ecosystem disservices. The photos show two grey partridges, a mouse and a jackdaw feeding on seeds in the experimental setup (from left to right). Pictures recorded by wildlife cameras set up by Matthias Tschumi and Cecilia Hjort.
The results underline that invertebrate, rodent and bird predators provide important ecosystem services such as weed and pest removal, but also that all animal groups can contribute to disservices. Surprisingly, birds were less important than rodents or invertebrates, highlighting the importance of soil-dwelling predators in agroecosystems. Although no clear influence of the landscape composition was found in these studies, they address an important topic for research and practice by considering positive and negative effects simultaneously. Payments for measures targeted at enhancing biodiversity and ecosystem services should account for trade-offs between ecosystem services and disservices, for instance by providing higher compensation for farmers in cases where net effects are likely to be negative.
Matthias Tschumi was during the time of this research a postdoctoral researcher at the Biodiversity unit in the Department of Biology at Lund University, Sweden and is now working at the Swiss Ornithological Institute.
Johan Ekroos is a research scientist at the Centre for Environmental and Climate Research, at Lund University.
Cecilia Hjort was during the time of this research a master student at the Biodiversity unit in the Department of Biology at Lund University.
Henrik G. Smith is a professor of animal ecology and director of the Centre for Environmental and Climate Research at Lund University.
Klaus Birkhofer is a professor and chair of ecology at the Brandenburg University of Technology (BTU) Cottbus-Senftenberg, Germany.
Tschumi, M., J. Ekroos, C. Hjort, H. G. Smith, and K. Birkhofer. 2018. Predation-mediated ecosystem services and disservices in agricultural landscapes. Ecological Applications. doi: 10.1002/eap.1799
Tschumi, M., J. Ekroos, C. Hjort, H. G. Smith, and K. Birkhofer. 2018. Rodents, not birds, dominate predation-related ecosystem services and disservices in vertebrate communities of agricultural landscapes. Oecologia. doi: 10.1007/s00442-018-4242-z