Invasive species could reap benefits from extreme weather

Extreme weather might be wreaking havoc across the globe, but some non-native plants and animals could be benefiting from the disasters, adding risk to the already threatened local species, according to a new study published on Monday.

Invasive species, often transported by human activity, are thought to be playing a major role in global extinction rates and the catastrophic declines of biodiversity threatening the well-being of people and the planet.

Heat waves, droughts, floods and other extreme events accelerated by global warming might be giving the often destructive invasive species an undesirable advantage, researchers found.

The harmful invaders experienced positive impacts from extreme weather almost a quarter of the time, nearly double that of natives, according to the study published in Nature Ecology & Evolution.

Local species were also more likely to suffer negative consequences from the weather disasters.

"EWEs (extreme weather events) might facilitate the establishment and or spread of non-native species and these two processes may combine together to pose high threats to biodiversity under continuing global change," said lead author Xuan Liu of the Chinese Academy of Sciences in Beijing.

Invasive species were only vulnerable to heat waves and storms, the study found. But native animals on land and in freshwater were negatively impacted across several factors, including survival rates, reproduction and body size, from all extreme weather except cold spells in freshwater.

The researchers looked at hundreds of previously published studies on responses of 187 non-native and 1,852 native animal species to extreme weather patterns in different habitats.

They found that differences in responses to unusual weather in species could be due to the death of native species during weather extremes, leaving a gap for invasive species to exploit.

Severe droughts, for example, increase the salt content of water, killing local invertebrates and fish while providing an opportunity for more salt-tolerant species to move in. 

Invasive species are also known for rapid growth rates and a greater competitive edge that might allow them to recolonize faster.  

Only in the case of marine animals were both natives and non-natives relatively immune to extreme weather, although native molluscs and corals are vulnerable to heat waves.

Invasive species are not a new problem, but they are a growing one.  

The intergovernmental science advisory panel for the UN Convention on Biodiversity revealed in a landmark report in September that invasive species were increasing at an "unprecedented rate" globally, costing more than $400 billion a year in damages and lost income. 

Invasive species mainly spread as hitchhikers on global trade and played a significant role in 60 percent of all documented plant or animal extinctions, it said.   

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