One of Earth’s Most Important Natural Climate Defenses is Disappearing — and Taking Animals With It

It's seriously bad news for biodiversity.

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High up in the mountains of Southeast Asia, humans are felling forests at an alarming clip for resources like palm oil and timber, jeopardizing the survival of many rare, endangered species that live in these tropical ecosystems.

New scientific research dives into the “alarming” and rapidly accelerating disappearance of mountain forests around the globe, especially in regions like Southeast Asia and Africa. The findings were published Friday in the journal One Earth.

“This study reveals for the first time that global mountain forest loss is accelerating, overturning our understanding of mountains as natural barriers to deforestation,” Zhenzhong Zeng, a co-author of the study and an associate professor at Southern University of Science and Technology in China, tells Inverse.

What’s Happening to the World’s Mountain Forests?

An image from the study shows where mountain forests have most rapidly disappeared around the world.

Zeng et al

In their research, Zeng and his team made the most comprehensive assessment to date of mountain forest loss around the world in the first two decades of the 21st century.

Zeng’s team traveled back in time — metaphorically — to the year 2000, when mountain forests covered 1.1 billion hectares of the world’s surface. For comparison: one hectare is roughly 2.5 acres — about two and a half football fields. The scientists projected forward, analyzing how the state of the world’s forests changed over time, relying upon global datasets on forest change to draw their conclusions.

The research team’s analysis finds we’ve lost a staggering 78.1 million hectares of mountain forests between 2000 and 2018. That’s roughly seven percent of the world’s mountain’s forests — an area larger than the size of Texas. That’s a lot of football fields.

The study reveals how we’ve rapidly increased our destruction of the world’s mountain forests since the turn of the century, reaching a peak in 2016 when mountain forest loss accelerated by 65 percent from the previous year. Forests in the tropics experienced the most rapid degradation of any mountain ecosystem as the rate of loss increased by 50 percent from 2000 to 2010.

Researchers outlined four key factors driving the destruction of mountain forests globally:

  1. Commercial forestry operations (42 percent)
  2. Wildfires (29 percent)
  3. Shifting agricultural cultivation (15 percent)
  4. Cash crops/commodity agriculture (10 percent)

The loss of mountain forests echoes across the planet, the researchers conclude, and was especially significant in Asia, South America, Africa, Europe, and Australia. While North America certainly lost a large share of mountain forests — 8.7 million hectares or 24 percent of the global loss — the rate of decline was not as rapid as in other parts of the world. The annual rate of forest loss in North America was half that of Africa, which lost its mountain forests at a rate of 0.48 percent annually.

“...mountain forests are being lost at an accelerating rate”

Overall, the forests most devastated occurred in Asia, especially in tropical countries like China, Indonesia, Vietnam, Malaysia, and Myanmar.

The reasons for the loss differed by country, but one big factor was that agricultural operations — for crops like rubber and palm oil — shifted to higher mountain elevations after deforesting lowland areas. In other places like Russia, climate change-driven wildfires were largely responsible for accelerating forest loss, whereas forest destruction in places like Portugal and the United Kingdom was driven primarily by commercial forestry.

“Since the turn of the 21st century, mountain forests have been increasingly exploited for timber and wood products, as well as to support emerging agricultural systems, such as boom crops and tree-based plantations, for example in Southeast Asia,” the researchers explain.

Even more troubling: the researchers found that forest loss wasn’t significant in plantations — large crops of a single tree species for commercial sale. Instead, mountain forest loss was largely occurring in the world’s natural forests, which we rely upon to support ecosystems and serve as carbon sinks — Earth’s built-in defense against global warming.

Why the Loss of Mountain Forests is Bad for Animals

A figure from the research shows how the degradation of mountain forests accelerated over time, putting countless species at risk.

Zeng et al

The loss of forests in themselves is devastating, but there’s a bigger problem underlying their destruction: mountains are home to approximately 85 percent of the world’s mammal, amphibians, and bird species. These mountain ecosystems serve as “important refuges” for large numbers of rare and endangered species according to the research.

Researchers found that tropical areas where the most rapid forest loss occurred overlapped with so-called “biodiversity hotspots” where large numbers of rare, endangered species reside. The scientists used the IUCN Redlist — a list of globally threatened species — to determine where forest loss overlapped with biodiversity hotspots.

Zeng says animals’ ability to move to higher elevations to escape the destruction of their habitat may be “limited” owing to factors like the landscape topography. Some endangered animals have evolved to thrive only in specific micro-habitats.

Four countries in Southeast Asia experienced the most rapid decline in tropical mountain forests: Indonesia, Madagascar, Vietnam, and Malaysia.

But researchers also found a significant decline in tropical mountain forest biodiversity hotspots in Africa, specifically in Zimbabwe, Guinea, Coˆte d’Ivoire, Madagascar, and Mozambique. Other countries where forest loss coincided with high biodiversity were Canada, Chile, and Mongolia.

How Can We Save these Ecosystems?

A tropical rainforest in Sumatra, Indonesia. The research finds the fastest loss of mountain forests has occurred in tropical Southeast Asian countries like Indonesia.


The findings were grim but also contained a nugget of hope: protected areas — set aside by the government or other entities for conservation — were effective in most countries in the world in deterring forest loss compared to non-protected areas.

“In all types of mountain biodiversity hotspots, relative forest loss inside [protected areas] was much less than outside, suggesting that [protected areas] within mountain biodiversity hotspots may be effective in limiting forest loss,” write the scientists.

Zeng says the development of protected areas is a “promising avenue” to limit the devastation of mountain forest loss, but the management of protected areas needs to be improved in some countries where enforcement and resources are lacking. There’s also a delicate balancing act involved, since people may be cutting down mountain trees for subsistence agriculture or to sell crops to earn a living after lower-lying forests have been depleted.

“Human livelihoods and wellbeing should also be considered when developing forest protection strategies and interventions,” Zeng adds.

Since factors driving deforestation vary depending on the country, future actions will require “regionally appropriate interventions” according to the study authors. In areas where large-scale agricultural operations are moving to exploit mountain forests, Zeng says we “urgently” need a greater commitment to safeguarding the rare species living in mountain forests.

“We hope to draw attention to the fact that mountain forests are being lost at an accelerating rate, putting biodiversity at risk,” Zeng concludes.

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