Today is Arbor Day, a holiday that celebrates the importance of trees. As such, it seems appropriate to talk about the role deforestation plays in global climate change.

According to the World Wildlife Federation, deforestation and forest degradation account for 15% of global anthropogenic carbon dioxide (CO₂) emissions. That makes it the second largest human-generated source of carbon dioxide in the atmosphere, behind only the burning of fossil fuels.

Forests are often called the “lungs” of our planet, as trees absorb CO₂ and release oxygen as part of the process of photosynthesis. As such, forests act as carbon sinks. When cut down, the trees not only stop absorbing CO₂, but they release it when they are burned or left to decompose. The WWF says we lose forests around the globe at the rate of 36 football fields every minute.

Deforestation is the large scale clearing of forests for other land uses. Its biggest drivers are agriculture and logging. In the tropics, where trees grow year round, forests are often cleared to make way for monoculture farms of palm oil or soybeans. While these crops also absorb CO₂, it is far less than the amount absorbed and stored by native forests.

Deforestation also has localized climate impacts. Without trees to evaporate ground water and release it as water vapor though the process of transpiration, local climates tend to get drier. When it does rain, runoff increases and accelerates the rate of soil erosion. Deforestation also means a loss of habitat for numerous species of plants and animals, which lends itself to a decrease in biodiversity.

Recognizing the scale at which deforestation is impacting global climate change, policymakers at the UN adopted a set of policies known as REDD (Reducing Emissions from Deforestation and Forest Degradation). They offer monetary incentives to governments in developing nations to maintain and manage their forests more sustainably.  In facing the challenges of climate change, mitigation efforts are needed on all fronts.