Non-native species appear to be better able to resist extreme weather, threatening native plants and animals and potentially creating more favourable conditions for invasive species under climate change. That’s the conclusion of a new study in the scientific journal Nature Ecology and Evolution.
Wildfires, droughts, heavy rainfall and storms are all increasing, and predicted to become more frequent throughout the next century due to human-driven climate change.
At the same time, humans are transporting more species into new areas, despite concerted global efforts to increase biosecurity across borders and to target the eradication of specific species. Some of these non-native species can go on to become invasive, damaging native ecosystems.
Capitalising on opportunities
Invasive species introduced by humans often possess traits that help them survive or even thrive when ecosystems are disturbed (perhaps by wildfire, a storm or human buildings).
Invasive plants are generally fast-growing, for instance, allowing them to quickly fill gaps before native species can recover from disturbances. They are also often very good at dispersing their seeds, allowing them to quickly colonise disturbed areas.
This is why scientists have long suspected that extreme weather and the success of non-native species could be linked.
If extreme weather removes native plants and animals, that increases the availability of resources such as water and space. Non-native species can then capitalise on these new resources to establish themselves.
Even more concerning is the potential for extreme weather and non-native species to interact, exacerbating their effect on native biodiversity. For instance, in a recent field experiment in the US, scientists deliberately started a fire which killed about 10 per cent of the longleaf pine trees in the area studied.
But in areas where an invasive grass – cogongrass, an Asian native – was allowed to establish itself alongside the pines, the fires had more fuel and were larger, hotter and burned for longer.
Where the scientists had added rain shelters to simulate drought conditions, the grass dried out further and the fires became much more lethal. A combination of drought and the invasive species meant longleaf pine mortality soared to 44 per cent.
Similarly, on the small Macquarie Island in the south west Pacific, a combination of extreme rainfall and the presence of invasive European rabbits reduced the breeding success of nesting black-browed albatrosses. Heavy grazing by the invasive rabbits reduced plant cover, exposing the albatross chicks to the harsh weather conditions.
Bad weather, good
for non-natives
To better understand how native and non-native species respond to extreme weather events, the scientists behind the new study reanalysed information from 443 peer-reviewed studies on how species responded to wildfires, droughts and storms. In all, they gathered data on 187 non-native species and 1,852 native species from all major animal groups. Their results suggest that native and non-native species may indeed respond differently to extreme weather. Across all studies, a total of 24.8 per cent of non-native species benefited from extreme weather events compared to only 12.7 per cent of native species. (The Conversation)
