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Forest and Climate

Forests have been called the Earth’s lungs because they release oxygen into the atmosphere after absorbing carbon dioxide during photosynthesis. The process helps stabilize global temperatures; because carbon dioxide is a greenhouse gas that causes climate change, plant biomass reduces global warming by scrubbing the atmosphere of the gas. Unfortunately, unprecedented levels of atmospheric carbon dioxide are choking forests that are also stressed by additional effects of climate change. Rising temperatures, changes in precipitation patterns and more frequent extreme weather events take their toll on the world’s forests. The relationship between forests and climate change is made even more complex due to deforestation, a process that sometimes turns forests into sources of carbon dioxide.

The combustion of fossil fuels releases carbon dioxide into the Earth’s atmosphere. In turn, these emissions produce climate change and global warming. Plants and forests limit these changes by removing atmospheric carbon dioxide and converting it into carbon through photosynthesis. The carbon is then stored in the form of vegetation. Forest soils made of organic matter also store carbon. Currently, the world’s forests store over a trillion tons of carbon — more than twice the amount present in the atmosphere.

In contrast, nearly 6 billion tons of carbon dioxide are released into the atmosphere annually as a result of deforestation. When forests are depleted, the stored carbon is released, making a depleted forest and climate change inextricably linked. The released carbon is a greenhouse gas that contributes to global warming.

The planet’s largest rainforest, the Amazon forest, provides a strong example of the link between forest and climate. The forest plays an important role in maintaining climate function both globally and regionally. Regional hydrologic cycles depend heavily on the forest, and the Amazon’s canopy layer helps regulate humidity and temperature.

The Amazon rainforest currently stores between 90 and 140 billion metric tons of carbon, but its size has diminished by nearly 20 percent in the last 40 years due to deforestation. As a result, the depleted areas of the Amazon release nearly half a billion metric tons of carbon every year. Scientists predict that an additional 20 percent of the rainforest will disappear in the next 20 years, resulting in even larger emissions of greenhouse gases and the continued loss of one of the Earth’s most biodiverse and important ecosystems.

The relationship between forest and climate change also affects the distribution of tree species. The territorial range of trees and other plants depends largely on precipitation patterns and temperature. As climate change alters these factors, the distribution of many tree species will change. Scientists believe that some tree species may move as much as 350 kilometers north in response to rising global temperatures, drastically changing the forest landscape worldwide. Many species will not be able to adapt to climate change quickly enough and may become extinct as a result.