In their latest research, Windsor et al. demonstrate the importance of considering multiple ecosystem services and disservices when designing plant mixes for field margin management.
Plants in field margins serve a multifunctional role, supporting a range of important ecological processes and ecosystem services. Management schemes to date, however, have focused on individual ecological processes/services (i.e., pollination or natural pest control). Indeed, Countryside Stewardship Grants to UK farmers and land managers explicitly promote the use of seed mixes designed to provide resources that support pollinators or supply food for winter birds.
However, by failing to consider potential non-target effects of the proposed plant mixes on the provision of other ecosystem services, these management schemes may incur unintended ecological consequences. For example, a plant mix designed to promote pollinators and thus enhance pollination of crops may also increase the abundances of pest herbivores and other insects associated with negative effects on crop plants.
Without an analytical framework to incorporate the effects of different plants on a range of beneficial and non-beneficial insects it is unclear the extent to which current management strategies may have wider positive or negative effects on important ecological processes.
Ecological networks, the complex webs of species interactions, offer a unique opportunity to develop such a framework. These complex interactions enable us to determine the direct and indirect effects that govern ecological processes, in turn providing a whole system framework with which we can assess linkages between the structure and function of ecosystems. In doing so, we can combine multiple types of networks involving the same sets of species into what we call multilayer networks (the layers being the different types of interaction e.g. plant-pollinator, plant-herbivore and plant-herbivore-parasitoid).
In this study, we developed a new method, based on multilayer ecological networks, to identify mixes of plant species that support high species richness of insects associated with ecosystem services (e.g., pollinators and parasitoids of pests) and low species richness of pest herbivores.
The aim was to understand the overlap in ecosystem service provision by plants and determine any potential trade-offs that might exist when managing field margins to deliver multiple ecosystem services. Through this, we wanted to develop a practical tool that farmers, land managers and policy makers can use to identify mixes of plant species that are optimal for supporting ecosystem services and minimising ecosystem disservices.
Our results showed that there were a number of trade-offs associated with different plant mixes aimed at increasing the provision of individual ecosystem services. For example, the pollinator plant mix maximised the species richness of pollinators, however, it also produced intermediate numbers of parasitoid and herbivore species.
When we took into account multiple services and disservices (pollination, pest control and herbivory) we were able to find a mix of plants that maximised pollination and pest control by parasitoids, whilst minimising herbivory.
These findings suggest that management which focuses on single ecosystem services may not be the optimal way of maximising the range of ecosystem services provided by plants in field margins. We therefore recommend that more attention be paid to developing plant-focused management strategies that account for effects across multiple ecosystem services. To help achieve this, we provide summaries of how to implement the data collection and analysis that we used in our study.
Developing new tools to understand agro-ecosystems is essential for achieving the ultimate goal of sustainable agriculture. Further research, however, is required to field trial how these management strategies will affect crop yields as mediated through the impact of plants on beneficial and non-beneficial organisms.
Read the full Open Access paper Identifying plant mixes for multiple ecosystem service provision in agricultural systems using ecological networks in Journal of Applied Ecology.