Chad Small writes:

Tree-planting is a cornerstone of numerous environmental and climate campaigns, and for seemingly good and logical reasons: When plants photosynthesize, they exchange carbon dioxide for oxygen.

The reality of planting trees to combat climate change is a bit more complicated. Planting the wrong trees in the wrong places can do more environmental harm than good. There is an ongoing debate as to whether reforestation will compete too much with necessary agriculture, or if trees—which can take a century to fully mature—will reach their peak carbon intake potential fast enough. And, as Sassan Saatchi, a senior scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, has said, tree planting will never be a substitute for decreasing fossil fuel emissions.

But there are other limits to using revegetation to combat the effects of climate change that haven’t been widely considered.

A team of atmospheric scientists have found that plants responding to elevated carbon dioxide in the atmosphere could increase regional flood risk—in some cases dramatically. Previously, the prevailing thought was that plants’ evapotranspiration rate—the process of exchanging carbon dioxide and water for oxygen—would increase in lockstep with atmospheric carbon dioxide levels. In reality, agricultural plants like wheat, rice, and cotton and most trees are more likely to see water vapor releases plateau as emissions climb. This could lead to potentially hyper-saturated soils, increasing flood risks and complicating water management and disaster planning. [Continue reading…]