From Plant Press, Vol. 24, No. 4, October 2021.
Thirty percent of the world's trees are threatened with extinction, according to the new State of the World's Trees report. The report, compiling work led by the Global Tree Assessment (GTA) and launched by Botanic Gardens Conservation International (BGCI), is one of the first assessments of the world's threatened trees and is the culmination of five years of research to identify major gaps in tree conservation efforts.
Examining the globe’s 60,000 tree species, it reveals that 30% (17,500) of tree species are currently at risk of extinction. That means there are twice the number of threatened tree species globally than threatened mammals, birds, amphibians, and reptiles combined.
The report reveals that globally over 440 tree species are right on the brink of extinction, meaning they have fewer than 50 individuals remaining in the wild. These species are found all over the world, from the Mulanje cedar in Malawi, with only a few remaining individuals on one mountain, to a species of alani (Melicope balloui) found only in Hawai’i that has not recently been sighted in the wild.
The report finds hope for the future, however, as conservation efforts led by the botanical community worldwide are growing. Identifying which trees are at risk and ensuring these are protected is the most effective way to prevent extinction and restore endangered species. The report reveals that at least 64% of all tree species can be found in at least one protected area, and about 30% can be found in botanic gardens, seed banks, or other ex situ collections, but further action is needed.
The State of the World’s Trees report brings together research from over 60 institutional partners, including botanic gardens, museums, forestry institutions, and universities worldwide, as well as more than 500 experts who have contributed to tree assessments in the last five years. The Department of Botany at Smithsonian’s National Museum of Natural History is one institutional partner, and several staff members from the department have served as experts on species assessment reports.
The greatest threats facing trees include habitat loss from agriculture and grazing, followed by over-exploitation from logging and harvesting. Climate change and extreme weather are emerging threats to tree species globally. As the temperature and weather of the world changes, many trees risk losing areas of suitable habitat, in both temperate and tropical regions.
At least 180 tree species are directly threatened by sea level rise and severe weather events. This threat is most severe to island species, including magnolias in the Caribbean. An increased occurrence of fire is a major threat to trees in Madagascar and has also been identified as a risk to US species of oak and Nothofagus trees in Australia and South America. Globally, land use change to agriculture alongside increasing global temperatures compounds the risk of fire to many tree species.
Tree species are the backbone of the natural ecosystem. They store 50% of the world’s terrestrial carbon and provide a buffer from extreme weather, such hurricanes and tsunamis.
Many threatened tree species provide the habitat and food for millions of other species of birds, mammals, amphibians, reptiles, insects, and microorganisms. The extinction of a single tree species could cause a domino effect, catalysing the loss of many other species.
Despite this, it has often been animals that have received most attention as requiring urgent protection. With a third of tree species on the verge of extinction, the State of the World’s Trees report hopes to raise awareness of the trees that are equally at risk and require action to prevent extinction.
The report indicates hope for the future if conservation efforts continue and further action is taken. BGCI has launched a new GlobalTree Portal, an online database tracking conservation efforts for trees at a species, country, and global level.
Both the report and portal show for the first time which trees need the most protection, where action is needed most urgently, and most importantly, where the gaps in conservation effort are. Recommended actions include extending protection of habitat for threatened tree species; ensuring threatened tree species, where possible, are conserved in botanic garden and seed bank collections; and expanding native and threatened tree planting programs, amongst others.
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