Emerald ash borer puts ash species on IUCN red list

Widespread and valuable ash tree species are on the brink of extinction due to an invasive beetle decimating their populations, according to the latest update of The IUCN Red List of Threatened Species.

Emerald ash borer - image: IUCN
Emerald ash borer - image: IUCN

The IUCN Red List now includes 87,967 species of which 25,062 are threatened with extinction. There are 268,000 flowering plants extant, with 21,411 evaluated and 11,370 on the red list, double the number of 1996.

IUCN director general Inger Andersen said: "Our activities as humans are pushing species to the brink so fast that it’s impossible for conservationists to assess the declines in real time. Even those species that we thought were abundant and safe – such as antelopes in Africa or ash trees in the U.S. – now face an imminent threat of extinction.

"And while conservation action does work, conserving the forests, savannas and other biomes that we depend on for our survival and development is simply not a high-enough funding priority. Our planet needs urgent, global action, guided by the Red List data, to ensure species’ survival and our own sustainable future."

UK chief plant health inspector Nicola Spence said last week emerald ash borer was one of the biggest concerns the UK is facing.

Five of the six most prominent ash tree species in North America enter The IUCN Red List as Critically Endangered – only one step from going extinct – with the sixth species assessed as Endangered. These species are being decimated by the invasive Emerald Ash Borer beetle (Agrilus planipennis). Three of them – Green Ash (Fraxinus pennsylvanica), White Ash (Fraxinus americana) and Black Ash (Fraxinus nigra) – are the country’s most dominant ash trees, comprising nearly nine billion trees in the forested lands of the contiguous U.S. 

Murphy Westwood, member of the IUCN Global Tree Specialist Group and director of global tree conservation at The Morton Arboretum, who led the assessment, said: "Ash trees are essential to plant communities of the United States and have been a popular horticultural species, planted by the millions along our streets and in gardens. Their decline, which is likely to affect over 80 percent of the trees, will dramatically change the composition of both wild and urban forests. Due to the great ecological and economic value of ash trees, and because removing dead ash trees is extremely costly, much research is currently underway across sectors to halt their devastating decline. This brings hope for the survival of the species."

The fast-moving Emerald Ash Borer beetle arrived in Michigan from Asia in the late 1990s via infested shipping pallets, and has already destroyed tens of millions of trees throughout the U.S. and Canada. It has the potential to destroy over eight billion ash trees as it spreads rapidly and can kill nearly an entire forest stand of ash within six years of infestation.

Due to a warming climate, areas which were previously too cold for the beetle are becoming more suitable for it to thrive, making it impossible to know how far it could spread in future.


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