International scientists led by Leeds University in the UK have discovered a 50% increase in the annual rate of mountain forest loss between 2001-2009 and 2010-2018, resulting in the loss of approximately 5.2 million hectares of mountain forests each year. The study, published in the journal One Earth, highlights the danger of rapidly decreasing habitats for over 85% of the world's bird, mammal, and amphibian species who live in mountain forests.
The authors, who aimed to explore the extent and global distribution of mountain forest loss, cited rapid agricultural expansion in mainland Southeast Asia and increased logging of mountain forests due to depletion of lowland forests or protection of lowland forests as the primary drivers of acceleration. Since 2000, the Earth has lost 78.1 million hectares or 7.1% of mountain forests, which is larger than the size of Texas.
The researchers also found that tropical mountain forests had the most loss, accounting for 42% of the global total, and the fastest acceleration rate. However, these forests also showed faster rates of regrowth compared to mountain forests in temperate and boreal regions. The study highlighted signs of tree cover regrowth in 23% of areas that lost forest.
Once protected from deforestation by their rugged location, mountain forests have been increasingly exploited since the beginning of the 21st century. The loss has occurred mainly in tropical biodiversity hotspots, putting increased pressure on threatened species, according to the scientists.
The findings emphasize the urgent need for global action to protect mountain forests and their biodiversity.
Logging was the biggest driver of mountain forest loss overall (42 per cent), followed by wildfires (29 per cent), shifting or "slash-and-burn" cultivation (15 per cent), and permanent or semi-permanent agriculture (10 per cent), though the importance of these different factors varied from region to region, the authors said.
Significant loss occurred in Asia, South America, Africa, Europe, and Australia, but not in North America and Oceania, they said.
To achieve their objectives, the team tracked changes in mountain forests on a yearly basis from 2001 to 2018.
They quantified both losses and gains in tree cover, estimated the rate at which change is occurring, compared different elevations and types of mountain forests - boreal, temperate, tropical - and explored the impacts of this forest loss on biodiversity, they said in the study.
"Knowledge of the dynamics of forest loss along elevation gradients worldwide is crucial for understanding how and where the amount of forested area available for forest species will change as they shift in response to warming," the authors wrote.
Protected areas experienced less forest loss than unprotected areas, but the researchers cautioned that this might not be enough to preserve threatened species.
"Regarding sensitive species in biodiversity hotspots, the critical issue extends beyond simply preventing forest loss," the authors wrote.
"We must also maintain the integrity of forests in large enough zones to allow natural movements and sufficient space for ranging species," they said.
The authors also emphasize the importance of considering human livelihoods and wellbeing when developing forest protection strategies and interventions.
"Any new measures to protect mountain forests should be adapted to local conditions and contexts and need to reconcile the need for enhanced forest protection with ensuring food production and human wellbeing," they said.