Increased global temperatures help invasive species establish themselves in ecosystems, new research led by a Swansea University bioscientist has shown.

The study, published by the Royal Society, gives an insight into the probable combined effects of species invasions, which are becoming more common, and global warming.

Climate warming and biological invasions result in the loss of species. They also alter the structure of ecosystems and the ways in which species interact.

While there is already extensive research on how climate change and invasions affect species and ecosystems, we know surprisingly little about their combined effect, acting together in synergy.

This is where the new study marks an important step forward. The work, funded by the EU Horizon program, involved Dr. Miguel Lurgi from the College of Science working with colleagues from the Institut National de la Recherche Agronomique (INRAE) and the Centre National pour la Recherche Scientifique (CNRS) in France.

The team used mathematical simulations to investigate how temperature influences invasions in complex food webs comprised of 30 species. They paid particular attention to the combined—synergistic—effects.

The aim was to provide a theoretical model for how ecological communities are likely to respond to the joint effects of warming and invasions.

The model accounted for factors such as reproduction and death rates, average species body size, and interactions between species—such as predators attacking prey.

The team simulated what happens when an alien species is introduced into an ecosystem. They then ran the simulation forward in time using 40 different temperature values from 0 to 40 degrees Celsius.

This allowed them to model the combined effects on the ecosystem of temperature rises and of the new species being introduced.

They analyzed the simulation results to assess the effects of temperature on food web properties before invasion, invasion success, and the effects of invasions on community structure and stability.

They found:

• Warmer temperatures modified community structure and dynamics that in turn facilitated invasions.
• Warmer temperatures mostly amplified the impacts of invasions on communities when compared with their colder counterparts.
• Temperature effects on invasions are mostly indirect and mediated by changes in community structure and stability.

Dr. Miguel Lurgi of Swansea University, lead researcher, said:

"Warming and invasions are driving major changes to our ecosystems, and it's essential that we understand their combined effects.

Our study provides a first step in that direction, analyzing the synergistic effects of temperature and invasions on communities.

Overall, we found that temperature and invasion act synergistically to increase the rate of species loss, creating smaller and more connected networks.

We have seen with COVID19 how mathematical modeling has been crucial in understanding the likely spread and impact of the virus.

Similarly, our work provides theoretical expectations for the likely response of ecological communities to the joint effects of warming and invasions."

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