SOURCE: Yale Climate Connections

DATE: April 4, 2019

SNIP: What happens within and immediately around a deforested area is obvious to anyone who has ever stumbled across a clearing in the woods. One new study shows that globally, forest cover makes land on average of 4°C (7.2°F) cooler. The effect is even stronger in dense tropical forests.

Two physical phenomena explain this beneficial effect of a forest. First, bare or sparsely-vegetated land is usually darker than leafy canopy. So a clearing generally absorbs more of the Sun’s energy than a forest and reflects less sunlight back into the sky.

Second, deforestation denies a plot of land the natural cooling mechanism driven by fluids circulating between trees’ roots and crowns. Trees sweat – or transpire – water vapor from the tiny pores in their leaves. The released moisture cools the space around them by the same process that chills an air conditioner unit’s air. Multiplied by the thousands of leaves that adorn typical trees, transpiration substantially lowers a forest’s temperature.

[The researchers] found that clearing 50 percent of a block of tropical forest raises temperature of nearby intact jungle by 1°C (1.8°F).

[Barry] Sinervo says he was “blown away” by the degree of deforestation-induced warming, especially in tropical forests, such as the Amazon. Climate change alone threatens the viability of these bastions of biodiversity. He says that for the past several decades, the effect of deforestation has been as great as that of climate change’s unflagging march, doubling the rising stress on tropical wildlife.

Eduardo Maedo, a research scientist at the University of Helsinki, says that the PLOS One paper strengthens the case that deforestation does profound damage beyond the boundaries of land that’s cleared. He’s conducting his own studies on local reverberations of forest loss. Such research “has direct impact on policy,” he says, by adding new arguments for protecting trees from being cut and for replanting trees after a forest has been removed.