Over the last 40 years, Great Britain’s ecosystems have become less resilient to the impacts of environmental change, according to new work published in Nature Communications this week. Researchers studying over 4,000 wildlife species found significant declines among animals that perform key functions including pollination and pest control.
Within a single ecosystem, various species have different roles in important services ranging from crop production to decomposition to climate regulation, which includes capturing CO2 from the atmosphere and storing it in tissues. While bees pollinate flowers, for example, earthworms decompose dead organic matter. Sometimes, the roles of different plants and animals overlap – and this "functional redundancy" helps buffer species losses. But while biodiversity has been declining at the global level, the impact on the resilience of ecosystem functions remains unknown.
To help clarify which functions are more at risk, University of Reading’s Tom Oliver and colleagues analyzed trends in the occurrence or abundance of 4,424 species of birds, mammals, invertebrates, and plants in Great Britain between 1970 and 2009. This allowed them to identify which functions were being carried out by which species.
Bees, flies, moths, butterflies, beetles, and wasps help transfer pollen when they visit flowers of the same species, while small predators ranging from ladybugs to birds are natural enemies of crop pests. The team discovered significant drops in the groups of species that are able to perform pest control and pollination services: 16 and 27 percent of species in the two respective groups have shown statistically significant declines.
Meanwhile, groups that perform duties related to decomposition (such as ants and millipedes) and carbon sequestration (vascular plants, mosses, and liverworts) appear relatively robust: Declines were observed in 7 and 10 percent of species, respectively.
Then, to see why some roles remained stable over time, the team separated the species that were already present in Great Britain before 1970 from those that arrived afterwards. New arrivals, they found, have mostly been species fulfilling carbon sequestration and decomposition functions. In theory, new arrivals could be invasive ones, Oliver explains to IFLScience. Only a small proportion of new arrivals seem to do damage, and they’ll need to be managed on a case-by-case basis. "What is needed is a more thorough assessment of both the potential benefits and costs of non-native species," he adds, "rather than black-and-white policies that either say ‘keep all non-natives out’ or ‘welcome to all non-native species!'"
As for pest control and pollination, the new arrivals weren’t sufficient to offset declines. That means that species vital to agriculture and food production may be less resilient to environmental change – and they’re being eroded rapidly.
Oak bush cricket by Gilles San Martin and Lesne’s earwig by Gary Farmer. Both provide pest control.
Image in the text: dark green fritillary butterfly by Tom Oliver.