Climate impact from loss of tropical forests 600% higher than thought

‘I had a hunch it was bad but I didn’t expect it to be this dramatic’ says Dr Tom Evans

Scientists looked at the 549 million hectares of tropical intact forests in the world. Pictured is a road for oil palm plantations in West Kalimantan, Indonesia (Rainforest Action Network)

The amount of carbon released from the loss of intact tropical forests is 626 per cent higher than previously thought, a new study has found.

Generally when scientists measure carbon emissions released by forests they look at deforestation.

However, this is only part of the story, according to the latest paper published in the Science Advances journal, which shows that forests are being damaged in ways previously unaccounted for.

Selective logging which damages the overall health of forests and wildlife losses from hunting are among the things harming them.

Scientists also took into account the amount of carbon which would have been sequestered if degraded forest had stayed intact.

“We’re looking at forest areas that we think are being missed when people look at forests in terms of climate change,” researcher Dr Tom Evans from the Wildlife Conservation Society (WCS) told The Independent.

“I had a hunch it was bad but I didn’t expect it to be this dramatic,” he added.

Scientists looked at the 549 million hectares of intact tropical forests in the world between 2000 and 2013, during which time 48 million hectares was destroyed. The three main blocks are in the Amazon, Congo basin and in the island of New Guinea.

Intact forests refer to areas free from significant human pressure. Only 20 per cent of tropical forests are “intact” but they store 40 per cent of carbon found in all tropical forests.

One thing researchers looked at was the edge effect: When forests are fragmented, more trees become exposed to the edge where there is less protection from strong winds, drought, invasive species and fires from neighbouring farmland.

These "edges" can be hundreds of metres wide and are significantly less healthy than areas further in.

“A bunch of pressures diffuse in through the edges. That is well understood to reduce the amount of carbon the forest can hold and eventually you end up with only three-quarters of the carbon you had before,” said Dr Evans.

Another significant pressure is the loss of wildlife from hunting.

“Lots of carbon-rich tree species depend animals for seed dispersal – they have big seeds so they need big animals to disperse them,” said Dr Evans. “However, hunters specifically take big animals and in fragmented areas, populations of elephants, tapirs, toucans and monkeys all get hunted out.”

This results in a loss of large trees which means less carbon can be held under the canopy.

The last key pressure the study looked at was selective logging which is when high value wood is removed from a forest without the area being deforested.

Once tracks have been made people go in to take out cheaper wood and eventually – when the path is well trodden – people take out low-value trees to use as firewood or charcoal.

Scientists did their study by looking at maps showing changes in the world’s forests, reviewing literature about these changes and examining the carbon impact it had.

Researchers often ignore these processes to make sure their research is on the safe side. Dr Evans said "90 per per cent of this information was in the public domain but was never put together properly.”

Lead researcher Sean Maxwell of WCS and the University of Queensland said: “Our results revealed that continued destruction of intact tropical forests is a ticking time bomb for carbon emissions. There is an urgent need to safeguard these landscapes because they play an indispensable role in stabilizing the climate.”

This study is the latest to show emissions need to be rapidly reduced globally if climate goals are going to be reached.

“Our research reveals that additional sources of carbon emissions are currently not being accounted for by national governments, because they’re not legally required to consider them,” said co-author Dr Alexandra Morel from the Zoological Society of London.

“Monitoring of these intact forests over the last decade has shown an acceleration in their loss, which would suggest that without more attention this unaccounted source of emissions will continue to grow.”

The United Nations runs a programme on Reducing Emissions from Deforestation and Forest Degradation (REDD+) which enables developing countries to receive financial incentives for enhancing carbon stocks.

REDD+ covers support for conservation of forests not under immediate threat. However, recently financial support and implementation has focused on areas with high rates of deforestation.

Dr Evans said: “The relative value of retaining intact tropical forest areas increases if one takes a longer-term view and considers the likely state of the world’s forests by mid-century – a milestone date in the Paris Agreement. Agricultural expansion, logging, infrastructure and fires reduced the global extent of intact forests by 7.2 percent between 2000 and 2013 alone, yet the eventual carbon emissions locked in by these losses have not been comprehensively estimated.”

Researchers want to look at the amount of carbon lost in intact forests outside of the tropics such as the vast boreal forests of Canada and Russia.