Forests cool the world even more than we think - here’s how

Forests are well-known for their role in absorbing CO2 that would otherwise warm the atmosphere.

Now certain ‘biophysical’ properties of forests – including how they distribute light, water and heat – have been shown to make them even more cooling.

Researchers in the United States and Colombia found these biophysical properties can increase the cooling effect of forests by almost another 0.5°C.

Biophysics involves using the laws of physics – the study of matter and energy – to better understand how living organisms work in the biological world.

It includes examining the physical properties of organisms and their molecules - for example, their size, structure and how they group together.

In this case, it involved studying the physical aspects of trees – like their wood, leaves and forest density.

The researchers looked at three main biophysical processes and characteristics in forests that directly impact climate.

The first two of these were albedo – a measurement of how trees reflect sunlight – and a process called evapotranspiration. This is how plants move water from the land to the atmosphere, through their roots and leaves.

The researchers also considered canopy roughness, which describes the density and distribution of trees and their leaves.

With their deep roots and high leaf area, these three biophysical factors made forests “very efficient” at moving both heat and moisture away from the Earth’s surface and into the atmosphere.

These processes stabilize the local climate by reducing extreme temperatures in all seasons and times of day. The biophysical effects of forest cover can “contribute significantly” to reducing climate risks like extreme heat and flooding at any latitude, said the researchers.

Forests and other land-based ecosystems like grasslands and tundra are already known to help to remove 29% of CO2 emissions a year. Adding the carbon in soils, forests contain almost as much carbon as is currently stored in the atmosphere, the researchers said.

They call for a better understanding of the combined effects of forest carbon and biophysical controls on both local and global climate. This is needed to “guide policy decisions” on reducing climate risks, adapting local communities and conserving biodiversity.

There is a growing body of evidence around the vital role forests play in combating climate change by absorbing carbon.

Forests absorb a net 7.6 billion metric tonnes of CO2 a year, scientists have found. But deforestation is a big threat.

About 15 billion trees are lost globally every year.

To respond to this, the World Economic Forum launched the Trillion Trees (1t.org) global reforestation initiative in 2020.

The initiative’s vision is to conserve, restore and grow one trillion trees by 2030 to help restore biodiversity and fight climate change.

The Forum also hosts the UpLink Trillion Trees Challenge, which calls for solutions and innovations to the loss of forests.

The economic value of forests could be up to $150 trillion – around double the value of global stock markets – according to Forum research.