‘Underestimated’ tropical forests hold key to cooling planet: report

The scientific community is unanimous that forests are our natural “air conditioners” on both a local and global scale, and that humanity’s future depends on them. While the world struggles to meet the 1.5C climate change target, a report published Thursday shows that, thanks to unique biophysical processes, tropical forests have an enormous and underestimated potential to keep the earth’s temperatures in check.

The report, The Unseen Effects of Deforestation: Biophysical Effects on Climate, explains why forests are so precious for the earth’s future and warns that their value is greatly underestimated by decision makers.

“The heart of the tropics is at the heart of the planet and these forests are critical for our survival,” said lead author Deborah Lawrence, a professor at the University of Virginia.

Forests are considered important ecosystems and an important way of absorbing carbon dioxide, the main greenhouse gas, from the atmosphere.

Deforestation is responsible for the intensity of hotter days, and the frequency of hot, dry summers. It also decreases regional and local rainfall.

For the first time, Lawrence and her fellow researchers were able to pinpoint the local, regional and global non-carbon dioxide benefits of specific forest zones worldwide, highlighting the extraordinary role played by tropical rainforests spanning Latin America, Central Africa and South-East Asia.

Not only do these forests absorb carbon on a large scale, they also provide cooling to the atmosphere thanks to a range of biophysical effects, which the authors say have so far been ignored by scientific models on climate change.

The study found that forests emit chemicals called Biogenic Volatile Organic Compounds (BVOCs) responsible for both cooling and heating effects, ranging from chemical compounds to turbulence and the reflection of light.

“I knew that tropical forests store a lot of CO2 and take up more every year, but I never added up the temperature impacts before – just the gigatons,” Lawrence told RFI.

“When you translate the CO2 into temperature and add the biophysical effects, tropical forests are doing a great service for us all.

“Their presence today is keeping us from experiencing the kind of climate we are trying to avoid by limiting warming to 1.5C rather than 2C. Deforestation brings on extremes that are similar to what we experience with an additional half a degree of warming.”

Impressive potential

 

The report, gathering together data from across the globe, is an attempt to show that forest impact is more complex that previous thought.

Other aspects of forests that enable them to minimise drought associated with extreme heat include their deep roots, high water use efficiency and high surface “roughness”, the report explains.

“These qualities allow trees to dissipate heat and move moisture higher into the atmosphere, which directly cools the local area and influences cloud formation and rainfall – which has ramifications far away.”

“When we cut them down, we see devastating impacts for our climate, food supplies and everyday life. The benefits of keeping forests standing are clear; it’s imperative that we prioritise their protection.”

Can we turn this around?

 

“As soon as a forest is planted, it begins to take up carbon dioxide; as the young canopy develops, it can start delivering more and more of the biophysical cooling benefits,” Lawrence says, adding that forests that cool the most are the ones that are biggest, with the largest areas and the largest trees.

“That means we need to keep the mature forests we already have. Turning this situation around in time depends fundamentally on a rapid reduction in emissions from fossil fuels and halting deforestation.

“We must start forest restoration now, knowing that the largest benefits will be felt after we have dramatically reduced our greenhouse gas emissions. Our existing forests are critical, but our ultimate success depends also on the forests we plant now.”

Lawrence points out the forests providing the most climate benefits are most at risk, especially from the production of commodities such as palm oil, paper, soy, and beef.

“Tropical forest biodiversity is unique and irreplaceable, but that fact alone has not led to effective protection,” she says.

Cop26 declaration

 

It is clear then, that the preservation of forests and reforestation are key to keeping global warming to 1.5C above pre-industrial levels, as per the 2015 Paris Agreement.

Almost a quarter of all anthropogenic emissions can be attributed to land use activity such as logging, deforestation and farming.

Over the last two decades for example, the Amazon basin has lost roughly 10,000 square kilometres every year, according to assessments based on satellite data.

In a report published in Nature, in July 2021, scientists confirmed the Amazon rainforest has become a source of carbon, rather than a carbon sink. Tree loss and a growing number of fires were to blame for the forest losing its power to capture C02.

• Summer wildfires emitted record amount of planet-warming CO2

 

To tackle this, 141 countries signed the Glasgow Leaders Declaration on Forests and Land Use during COP26 last November, committing to halting and reversing forest loss and degradation by 2030.

The pledge is backed by almost $20 billion in public and private funding and is endorsed by more than 100 leaders representing over 85 percent of the world’s forests, including the Amazon rainforest, Canada’s northern boreal forest and the Congo Basin rainforest.

• France’s largest bank pledges to stop funding firms behind Amazon deforestation

 

The signatories include Brazil and Russia, which have been singled out for accelerating deforestation in their territories, as well as the United States, China, Australia and France.

One of the clauses of the declaration includes referring to the management of locals and indigenous groups with generations of preservation knowledge.

 

The European Union in November also put forward a draft law requiring companies to prove their global supply chains are not contributing to the destruction of forests, specifically for the industrial-scale production of beef, soy, timber and palm oil.

Long way to go

 

“Forests have been lost due to market failure,”  Kevin Conrad, Special Envoy on Climate for Papua New Guinea and Executive Director of the Coalition of Rainforests told RFI at the Cop26 summit.

“We value the wood, we value what we can plant on the land, and until we value forests for their eco services, like pulling carbon out of the atmosphere, helping stabilise our rain cycle, until forests are more valuable alive than dead – we are going to constantly lose our forests.

“So that’s why paying for the carbon in standing forests, to keep them standing, is an important part of the solution and that’s what we are trying to accomplish.”