When ecosystems take with one hand and give with the other

Assessing the costs and benefits small rodents present to farmers, Associate Editor, Jonathan Rhodes comments on the recent article by Fischer et al. Ecosystem services and disservices provided by small rodents in arable fields: Effects of local and landscape management.

We all know that ecosystems provide a wealth of benefits to humans and there is now a whole rapidly growing discipline in this area focused on ‘ecosystem services’. But we often forget that ecosystems can produce disservices as well and services; that is, they can reduce, as well as improve human wellbeing. For example, predators can be problematic for farmers when they result in stock losses, but can also limit the overabundance of prey species that can, in turn, benefit farmers (although these may be different farmers from those suffering stock losses). When making management or policy decisions that influence the presence, or otherwise, of particular ecosystem processes, understanding the positive and negative consequences of the decision is crucial. Otherwise we end up ignoring key aspects of the costs and benefits when evaluating a management action.

Organic wheat field in Germany (photo taken by Friederike Riesch).

In their new article, Fischer et al. aim to better understand both the benefits and costs of small rodents to farmers. Small rodents are ubiquitous in agricultural systems and understanding when to control rodents, or not to control rodents, is a key question in agricultural land management. Ultimately, this depends on the costs and benefits of small rodents, which is often unknown. Interestingly, Fischer et al. recognise that the same organisms can provide both benefits and costs and aim to quantify these ecosystems services and disservices for voles and mice. Both these species can potentially provide benefits to farmers through weed seed removal, but are also potentially costly due to removal of crop seeds and crop damage. They used agricultural fields in Germany to quantify these effects and assessed both local- and landscape-scale drivers of abundance, wheat seed removal, and harmful weed seed removal and crop damage.

Wheat field overgrown with Galium aparine (photo taken by Friederike Riesch)

A key finding was that the rate of wheat seed removal (a disservice) was up to three times higher than weed seed removal (a service), suggesting that disservices outweigh services. Further, voles were associated with crop damage, especially when crops were at high densities and wheat height was low, also indicating the importance of disservices from voles. Their models also indicated the conditions under which disservices may be lowest; that is, under low crop densities and high wheat heights. But the study found that there were complex relationships between landscape-scale and local-scale variables, the abundance of rodents, seed predations and crop damage. Although not discussed in the study, it’s possible that these complex interactions indicate that the nature of services and disservices that each organism provides are context dependent. This is a concept that had been suggested previously and is an important area for further investigation for achieving better predictive understanding of ecosystem services and disservices (see Rasmussen et al. 2017).

Functioning ecosystems are vital for agricultural production, but understanding which bits of ecosystems are beneficial and which bits are not beneficial is a major challenge. It is unlikely that there are clear-cut principles or rules that identify the beneficial and non-beneficial bits, but Fischer et al. make an important empirical advance in quantifying services and disservices and potential drivers of these components.

Read the full Open Access article Ecosystem services and disservices provided by small rodents in arable fields: Effects of local and landscape management in Journal of Applied Ecology.

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