The Impact of Deforestation on Global Mercury Emissions

Monday - April 1 2024, 20:41 UTC - 1 year ago

About 10% of human-made mercury emissions are due to deforestation, with the Amazon rainforest playing a major role as a mercury sink. Efforts to curb deforestation and promote reforestation could significantly reduce mercury pollution, but should not replace overall pollution control efforts. Mercury is absorbed by plants and then can become a health concern when it accumulates in water bodies. Addressing deforestation-related emissions is crucial in reducing global mercury pollution.

About 10 percent of human-made mercury emissions into the atmosphere each year are the result of global deforestation, according to a new MIT study. The world's vegetation, from the Amazon rainforest to the savannahs of sub-Saharan Africa, acts as a sink that removes the toxic pollutant from the air. However, if the current rate of deforestation remains unchanged or accelerates, the researchers estimate that net mercury emissions will keep increasing.

The researchers' model shows that the Amazon rainforest plays a particularly important role as a mercury sink, contributing about 30 percent of the global land sink. Curbing Amazon deforestation could thus have a substantial impact on reducing mercury pollution.

The team also estimates that global reforestation efforts could increase annual mercury uptake by about 5 percent. While this is significant, the researchers emphasize that reforestation alone should not be a substitute for worldwide pollution control efforts.

Scientists have recently begun to quantify the role of the terrestrial biosphere in the global mercury cycle. Plant leaves absorb mercury from the atmosphere, similar to how they absorb carbon dioxide. However, unlike carbon dioxide, mercury does not serve a biological function in plants and stays within the leaves until they fall to the forest floor. From there, the mercury is absorbed by the soil.

The major concern with mercury is its ability to become methylated by microorganisms in water bodies. Methylmercury, a potent neurotoxin, can then bioaccumulate in fish and pose a risk to humans who consume them. The researchers stress that addressing deforestation-related emissions should be a part of global solutions to reduce mercury pollution.

The study, published in Environmental Science and Technology, was led by Ari Feinberg and Noelle Selin from MIT's Institute for Data, Systems, and Society (IDSS) and Department of Earth, Atmospheric and Planetary Sciences. Co-authors include Martin Jiskra, a former Swiss National Science Foundation Ambizione Fellow at the University of Basel; Pasquale Borrelli from Roma Tre University in Italy; and Jagannath Biswakarma, a postdoc at the Swiss Federal Institute of Aquatic Science and Technology.

In conclusion, this study highlights the significant impact of deforestation on global mercury emissions and emphasizes the need for comprehensive solutions to address this source of pollution.