22 September 2014
Last week, Nadine Unger, an assistant professor at Yale University, published an opinion piece in The New York Times stating that the way to save the planet was to not plant trees. This opinion was wrong at so many levels that it is hard to cover them all here. There are many reasons why we need to protect forests and to plant trees—protecting water supplies, reversing the loss of biodiversity, ensuring that we have pollinators for crops, and sequestering carbon to reduce human-induced climate change.
The article opens with a discussion of the international REDD+ (Reducing Emissions from Deforestation and forest Degradation) mechanism, which aims to reduce tropical deforestation and enhance carbon removals from the atmosphere by re-growing tropical forests. Unger says it won’t work, pointing to an old argument about the offsetting effects of carbon release and the increase of energy reflection when forests are removed—the so-called albedo effect. The argument recognized that forests are dark (look at an aerial photo or a Google Earth image) and absorb solar energy, while agricultural fields and pastures are lighter and reflect solar energy. It’s the reason why a black car sitting in the sun with the windows closed gets hotter than a white one. So: forests absorb energy and heat the lower atmosphere. A 2007 study led by G. Bala (and others) published in Proceedings of the National Academy of Sciences showed clearly that globally deforestation would lead to cooling. The albedo effect surpasses the carbon effect in the energy balance, and the Earth cools when forests are removed.
However, and this is an important “however” for this discussion, when the authors looked at how the carbon and albedo effects played out at different latitudes, they concluded that the albedo effect overwhelmed the carbon effect at high latitudes (northern temperate and boreal forests) and the carbon effect overwhelmed albedo at low latitudes (the tropics). Stopping tropical deforestation and increasing tree planting in REDD+ countries, where the albedo effect is smaller than the carbon effect, makes sense from an energy balance point of view. This is why the international effort focuses on stopping tropical deforestation and rehabilitating degraded tropical forests. There is no REDD+ mechanism proposed for northern countries.
Read more from CIFOR
The original NY Times Op-ed is here
Another response piece signed by a group of scientists appears in Mongabay
Steve Schwartzman of Environmental Defense Fund also responded to the op-ed here