An area of mountain forest larger than the state of Texas has been lost since 2001, with the amount disappearing each year accelerating at an “alarming” rate, a study warns.
Scientists found 78m hectares (193m acres) of mountain forest have been lost across the world in the past two decades, which is more than 7% of all that exists. The main drivers of loss were logging, the expansion of agriculture and wildfires.
Mountains are home to more than 85% of the world’s birds, mammals and amphibians. These habitats were once more protected than their lowland equivalents because their rugged terrain made them less accessible, the paper notes. Today, they are increasingly threatened as humans exploit harder-to-reach areas of the planet, and lowland forests are given greater protection.
“Our global analysis of mountain forest loss identifies an alarming acceleration over the past two decades,” the researchers, led by scientists from the University of Leeds and the Southern University of Science and Technology in China, wrote in the paper, published in the journal One Earth.
They found that logging was responsible for 42% of mountain forest loss, wildfires for 29%, slash-and-burn cultivation 15% and semi-permanent or permanent agriculture 10%.
The researchers tracked changes in forests between 2001 and 2018, documenting both increases and decreases in tree cover, and working out possible impacts on biodiversity. They found that Asia, South America, Africa, Europe and Australia were all badly affected. Much of the loss in northern Asia was due to wildfires, especially in large parts of Russia. Droughts and bushfires led to significant losses in Australia.
The annual rate of loss rose sharply after 2010, increasing by 50% in 2010-2018 compared with 2001-2009. Expansion of agriculture and logging in the highland areas of south-east Asia was found to be a key driver. During the period of study, more than half of global forest loss happened in Asia.
The climate crisis is putting pressure on specialist – and often sensitive – mountain wildlife, as warmer temperatures force species to move to higher ground. At some point, they are likely to run out of suitable habitats, a process known as the “escalator to extinction”.
Previous studies have shown that alpine plants are not keeping up with climate breakdown, with invasive species colonising the tops of mountains faster. Botanists working in the Scottish Highlands also found Britain’s rarest mountain plants were retreating higher.
In this latest paper, researchers warned: “Mountain forests are undergoing dramatic changes in many regions due to their sensitivity to climate change and anthropogenic pressures, which will become a major threat to mountain species.”
More than 40% of the total loss was in tropical mountain forests, which are considered biodiversity hotspots, putting even more pressure on threatened species. Zhenzhong Zeng from Southern University of Science and Technology, one of the paper’s authors, said: “What needs our attention is that mountain forest loss has encroached on areas of known high conservation value to terrestrial biodiversity, especially in the tropics. Various types of agriculture expansion and forestry activities are key drivers there.”
The paper found that creating protected areas within biodiversity hotspots lowered the rate of loss. “Increasing the area of protection in mountains should be central to preserving montane forests and biodiversity in the future,” it said.
Dr Marco Mina, a researcher at the Institute for Alpine Environment, Eurac Research, in Italy, who was not involved in the study, said: “My overall opinion is that the use of large-scale data such as remote-sensing satellite products are a great tool to monitor forest change in almost real time. However, we should be cautious to draw global conclusions based solely on remote-sensing products.
“A forest that is well managed through a careful planning process can still provide high levels of habitat for plants and animal species.”
• The headline of this article was amended on 20 March 2023 to remove a reference to “alpine” wildlife. As the article states, the study refers to losses in forest, not alpine, zones.
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