Let’s plant more trees to fight drought, increase rainfall and tackle climate change

Climate change is taking toll across the world in terms of extreme weather conditions, heat waves and drought. Trees can help mitigate climate change as it can capture huge amount of carbon dioxide.

According to a study published in the July edition of the scientific journal Nature Geoscience, converting agricultural land into forests could boost summer rainfall by an average of 7.6%, potentially offsetting some effects of global warming. It says land cover changes can affect the climate by alternating the water and energy balance of the land surface.

Numerous modeling studies have indicated that alterations at the land surface can result in considerable changes in precipitation. Forests are estimated to increase downwind precipitation in most regions during summer. In the latest study, researchers used an observation-based continent-scale statistical model to show that converting agricultural land in Europe triggers substantial changes in rainfall across the continent, not only locally, but also downwind from the forests. To determine which lands are suitable, researchers used a “global reforestation potential map”, which took into consideration sustainability, only including areas where reforestation would not threaten food and fibre security.

Ronny Meier, the study’s lead author, said reforestation can only happen over grazing lands and not over crop lands, under the assumption that in the future, people will consume less animal products and we will therefore have grazing lands available. He highlighted the rough surface of forests. “Forests typically have a higher surface roughness than agricultural land, inducing more turbulence and slowing movement of precipitating air masses, or heavy clouds, causing them to rain locally over the forests. This increased surface roughness exists also in urban areas with high buildings and has contributed to a rise in rainfall over and near cities.”

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Meier said the surface roughness factor, however, might also contribute to a drop in precipitation in certain regions downwind from forests in winter. “It could have the effect that moist-air masses or frontal systems that come from the ocean, from the west, are slowed down by forests and cannot propagate very well into the interior of the continent.”

Earlier studies have highlighted that large-scale deforestation reduces rainfall in some areas by up to 30%, and reliable rainfall in continental interiors of Africa, Australia and elsewhere appears to depend on maintaining relatively intact and continuous forest cover from the coast. Transforming landscapes from forest to fields has at least as big an impact on regional climates as climate change.