Temperature difference of 4 degrees

Scientists of eight universities have quantified the temperature difference between sites within forests and outside, for the first time across the globe. Measurements occurred at 98 locations spread across five continents, in the tropics, temperate zone and northern boreal forests.

The data show that the maximum temperature in forests is, on average across the globe, 4 degrees lower than outside forests.

This knowledge will result in better predictions on the impact of climate warming on forest biodiversity.

A research study aimed at establish "shadow trees" over a coffee plantation to get a cooler microclimate. Photo: Kristoffer Hylander

Forests as thermal insulation

“With their foliage and branches in the canopy, trees create a thermal isolating layer above the forest”, explains prof. Pieter De Frenne. “For this reason, summer maximum temperatures are much lower inside forests than outside. In the winter and at night, this pattern is reversed and forest temperatures are, on average, 1 degree warmer.”

“Our new data show that forest temperatures are on average 4 degrees cooler than outside temperatures when it is warm. Summer heat waves are thus strongly moderated below the tree canopy. Plants and animals inside forests will thus experience the current warming trend to a lower degree than species not living in forests”, says De Frenne. “Since forests cover a quarter of the land surface of the globe and harbour two thirds of all biodiversity, this has important implications for predictions on the impact of climate change.”

Prefessor Kristoffer Hylander at Department of Ecology, Environment and Plant Sciences comments:
"For example, climate warming and thus the effects on forest ecosystems may be overestimated".

Buffer against climate warming

For the first time, the researchers also show that with increasing temperatures, the buffering capacity of maximum temperatures of global forests also increases. The warming of maximum air temperatures within forests is thus probably lower than previously anticipated.

De Frenne: “Even though temperatures outside forests continue to increase, temperatures within forests do not necessarily follow that same trend. The decoupling between temperatures within forests and temperatures outside simply increases. Forests can therefore truly be considered a buffer against climate warming. Accordingly, our findings stress the need to conserve our existing forests and enhance reforestation efforts.

More information

The paper in Nature Ecology & Evolution.

Professor Kristoffer Hylander
Department of Ecology, Environment and Plant Sciences


telephone: +46765 525267

Professor Pieter De Frenne
Faculty of Bioscience Engineering, Ghent University


telephone: 0497 82 15 02