Mountain forests are disappearing at an accelerating rate, putting biodiversity at risk

More than 85% of the world’s bird, mammal and amphibian species live in mountains, especially in forest habitats, but researchers report in the journal One Earth on March 17 that these forests are disappearing at an accelerating rate . Globally, we have lost 78.1 million hectares (7.1%) of mountain forests since 2000, an area larger than the size of Texas. Much of the loss has occurred in tropical biodiversity hotspots, putting increasing pressure on threatened species.

Although their rugged location once protected the montane forests from deforestation, they have been increasingly logged since the turn of the 21st century as lowland areas become depleted or subject to protection. A team of scientists led by Xinyue He (@xinyue_he), Dominick Spracklen and Joseph Holden from the University of Leeds in the UK, and Zhenzhong Zeng from the University of Southern Science and Technology in China wanted to study the extent and the global distribution of mountain forests. loss.

To do this, the team tracked changes in montane forests on an annual basis from 2001 to 2018. They quantified both tree cover losses and gains, estimated the rate at which change occurs, compared different altitudes and types of montane forest — boreal, temperate, tropical — and explored the impacts of this forest loss on biodiversity.

“Knowledge of the dynamics of forest loss along elevational gradients around the world is crucial to understanding how and where the amount of forest area available to forest species will change as they move in response to warming. “, write the authors.

Logging was the main driver of mountain forest loss overall (42%), followed by forest fires (29%), shifting or ‘slash-and-burn’ cultivation (15%) and l permanent or semi-permanent agriculture (10%). although the importance of these different factors varied from region to region. Significant losses occurred in Asia, South America, Africa, Europe and Australia, but not in North America or Oceania.

Worryingly, the rate of mountain forest loss seems to be accelerating: the annual rate of loss increased by 50% between 2001-2009 and 2010-2018, when we lost around 5.2 million hectares of mountain forest. mountain per year. The authors write that this acceleration is likely due in large part to the rapid expansion of agriculture in the mountainous regions of mainland Southeast Asia, as well as increased logging in the forests of mountain due either to the depletion of lowland forests or to the protection of these lowland forests.

Tropical montane forests have suffered the most loss – 42% of the global total – and the fastest rate of acceleration, but have also experienced a faster rate of regeneration than montane forests in temperate and boreal regions. Overall, the researchers observed signs of regrowth of tree cover in 23% of the areas that lost forest.

Protected areas have suffered less forest loss than unprotected areas, but researchers warn that this may not be enough to preserve endangered species. “When it comes to sensitive species in biodiversity hotspots, the critical issue goes beyond simply preventing forest loss,” the authors write. “We also need to maintain forest integrity in areas that are large enough to allow natural movements and enough space for species that move.”

The authors also highlight the importance of considering human livelihoods and well-being when developing forest protection strategies and interventions. “Any new measures to protect mountain forests must be adapted to local conditions and contexts and must balance the need for enhanced forest protection with the guarantee of food production and human well-being.”

This research was supported by the Southern University of Science and Technology, the University of Leeds and the National Natural Science Foundation of China.

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