Study: Decaying Urban Greenery Plays a Surprising Role in Carbon Emissions


A recent study focusing on "the L.A. megacity" found that urban greenery added a small unexpected amount to the region's overall output of carbon dioxide.

A new study tracing the sources of carbon dioxide, the most significant human-generated greenhouse gas, reveals the unexpectedly large influence of vegetation in urban environments.

Burning fossil fuels in densely populated regions greatly increases the level of the greenhouse gas, carbon dioxide. The largest carbon dioxide sources are cars, trucks, ports, power generation, and industry, including manufacturing. Urban greenery adds CO2 to the atmosphere when vegetation dies and decomposes, increasing total emissions. Urban vegetation also removes this gas from the atmosphere when it photosynthesizes, causing total measured emissions to drop. Understanding the role of urban vegetation is important for managing cities' green spaces and tracking the effects of other carbon sources.

A recently published study showed that among the overall sources of carbon dioxide in urban environments, a fraction is from decaying trees, lawns, and other urban vegetation. The contribution is modest – about one-fifth of the measured CO2 contributed by the urban environment – and varies seasonally. This was more than researchers anticipated and underscores the complexity of tracking urban carbon emissions.

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