In the past, mountain forests were often spared as steep slopes and high elevations made deforestation more difficult.
Southeast Asia was once largely covered in dense rainforests, but intense forest clearing over the past decades has denuded much of the tropical region of its forest cover.
On the island of Borneo, for instance, 5.9 million hectares of trees were lost between 2004 and 2017 to logging, land-clearing and conversion activities.
The result has been an appalling loss of biodiversity with numerous endemic species from Indochinese tigers to Asian elephants to Bornean orangutans having been driven to the edge of extinction across the region.
Clearing forests in Southeast Asia has global effects too. Accelerating forest clearance at ever higher altitudes across the region is driving increases in carbon emissions, according to scientists from the University of Leeds in the United Kingdom.
After lowland forests have already been decimated, now relatively untouched forests are being cut down at ever higher altitudes on steeper slopes. Consequently, more than 400 million metric tons of carbon are released into the atmosphere of the planet every year, which fuels climate change and reduces the ability of the region’s thinning forests to store carbon effectively.
The vast and scenic region contains around half of all tropical mountain forests in the world, which are rich in biodiversity and carbon stocks, but the British scientists’ analysis of high-resolution satellite data has revealed an increasing loss of forest cover at higher altitudes across Southeast Asia.
In fact, deforestation on mountains has been accelerating over the past decade. Forest clearing for agricultural land at higher elevations has accounted for a third of total forest loss in the region in this new century, the experts say.
Between 2001 and 2019, the researchers found, the average annual forest loss around the tropical region was 3.22 million hectares a year, of which as much as 31% of deforestation took place on mountains. Over the past decade the average altitude of forest loss has crept up by 150 meters and has moved onto steeper slopes where forests have higher carbon density than on the lowlands, the scientists say.
As a result of this trend, there has been an annual carbon loss of 424 million metric tons a year across the region. Meanwhile, the rate of deforestation has been accelerating in recent years, especially in countries such as Myanmar (formerly Burma) and Laos.
“In the past, mountain forests were often spared from clearance because steep slopes and high elevations made deforestation more difficult,” explains Prof. Dominick Spracklen, an expert at Leeds’ School of Earth and Environment.
“These mountain forests are amazingly rich in biodiversity and are crucial stores of carbon, so it is worrying to see that the frontier of deforestation is now moving upwards into the mountains of Southeast Asia,” Spracklen adds. “Loss of these forests will be a devastating blow for nature and will further accelerate climate change.”
Biodiversity on mountains around the region is expected to suffer further losses while continued deforestation at higher elevations will also impact the region’s environment negatively.
“Forested mountains are critical zones for biodiversity, future climate resilience, water supplies and carbon storage,” says Prof. Joseph Holden, from Leeds’ School of Geography.
“The loss of forests at higher elevations in mountain regions of Southeast Asia over the last 20 years is therefore of major concern, particularly given that these regions are also concentrated zones of sensitive species and where carbon stocks are high,” he adds.