More than one in five species of maple trees, whose rich colours are one of the striking sights of autumn, are at high risk of extinction, experts warn.
The latest “Red List” for maples or Acers, published by Botanic Gardens Conservation International (BGCI), reveals that 36 out of the 158 species, some 23%, are at high risk of extinction in the near future in the wild.
It shows that more than a third of maple species are facing a loss of habitat as a result of urban development and increased agriculture, while timber harvesting is also a major threat.
Acers are largely native to the temperate parts of the northern hemisphere, though their range extends to subtropical and tropical regions and species are found as far south as Indonesia in the southern hemisphere.
Maples are popular as ornamental trees in parks and gardens, while in woodlands they provide a key component of the natural ecosystem.
The turning of maple leaves to an array of red, purple, russet and gold in autumn is eagerly anticipated by nature lovers. They are a source of maple syrup, and they provide an important timber crop in some countries.
The report, part of the International Union for Conservation of Nature (IUCN) Red List of threatened species, is contributing to a global tree assessment to analyse the status of all tree species by 2020.
It reveals seven species are critically endangered, the highest level for risk of future extinction, while 14 are endangered and 15 are vulnerable to extinction.
Two of the closest relatives to the North American sugar maple, which produces maple syrup, are listed as critically endangered.
That includes a maple from Mexico which was only discovered as a new species in the last few years and which is at risk from climate change in its cloud forest home and threatened by grazing, logging and forest fires.
But more than seven in 10 Acer species (71.5%) are not at risk, and the only species found in the UK, the field maple, is not under threat.
China is home to the largest proportion of maple species, with 92 species.
Some 14 of the 23 Acers that are at risk of extinction in China are only found in the country, with limited geographical ranges, small populations, and the threat of urban sprawl.
Species which are widespread across areas such as Asia or North America are generally not at risk.
The report said that while conserving at-risk species in their natural habitat in the wild is the best option, “ex situ” collections such as botanic gardens and seed banks is an insurance policy against extinction.
Some 14 species of maple are currently entirely absent from these kind of collections, including four critically endangered species.
The report recommends adding missing Acers to collections and making sure there is genetic diversity, as well as assessing whether Acer species are in protected areas in the wild, with a potential to expand those areas.
Conservation plans should be developed for the most threatened species, and maples which are not at risk should also be monitored to make sure populations are maintained.
Douglas Justice, associate director at the University of British Columbia Botanical Garden, Vancouver, the lead institution of the Global Conservation Consortium Acer, said that time was running out for the world’s biodiversity.
“And as robust as Acer species are, they are certainly not immune,” he said.
“Over only a few short years I’ve personally seen increased cutting and alarming loss of maple habitat in the forests of south-east Asia. This is happening nearly everywhere that rare maples exist.
“And because of climate change, the narrow habitats that support species at the margins of arid places and at the tops of mountains, are quickly disappearing.
“We still have an opportunity to save species from extinction, but it will take expertise and resources, and the coordinated, collaborative efforts by the world’s botanical gardens to make it work.”