Changing rainfall patterns impact soil invertebrate biodiversity

Human destruction of natural habitats and climate change are probably reducing invertebrate populations in many regions. We still don’t have much information about threats to flying invertebrates, but we have even less information for those that live in the soil. This is despite the fact that soils are teeming with life. Did you know that they are home to over over 7 million invertebrate species – around one third of all invertebrates in the world?

A new study, published in the journal Global Change Biology, aimed to tackle this lack of information, by looking at how changes in rainfall caused by climate change affect soil invertebrates in forests. The study, which is the largest of its kind, compiled data from 46 forests around the world, finding that droughts reduce the number of soil invertebrates by around 35%, while increases in rainfall lead to increases of a similar magnitude.

Importantly, the international team from six different countries, led by researchers from the Basque Centre for Climate Change in Spain, found that the effect of rainfall changes depend on an animal’s size: groups like springtails and mites were more severely affected than smaller animals like nematodes or larger animals such as beetles.

Before this study, scientists had not made the link between the size of soil animals and the potential effects of environmental threats. These new findings have far-reaching implications for our ability to predict future responses of soil invertebrates to climate change as well as their potential impacts on soil functioning and health.

The variation in impacts between different groups is important because the species that are most affected by changes in rainfall include many detritivore species. These species help to improve soil health by breaking down the dead leaves that blanket forest floors. In the long term, reductions in their abundance might threaten ecosystem services like nutrient cycling that help to support tree growth in forests on which we depend for carbon storage and provision of wood for timber.

Another implication is that soil invertebrates in different regions will be affected differently. For example, forests in regions where climate change is causing an increase in droughts, like southern Europe and central America, will see decreases in the abundance of soil invertebrates. On the other hand, in regions where rainfall will increase, like northern Europe and North America, forest soil invertebrates can be expected to increase.

So what can we do to tackle the threat of changes in rainfall to soil invertebrates? First and foremost we should focus on combating the climate crisis by reducing our carbon footprints by flying less, eating less meat, and making our homes more energy efficient.

However, even if we manage to reduce carbon emissions, we still face dangerous climate change and so we need to change how we manage ecosystems. One promising way to reduce the impacts of droughts on soil invertebrates is by spreading mulch on forest soils, which acts like a sunshade to protect against hot and dry conditions.

To tackle the impacts of the climate crisis on soils we urge decision-makers to take the threats to forest soils seriously and to fund and promote adaptations to current management.

This article was written by Phil Martin (BC3 – Basque Centre for Climate Change).