If we want to achieve Net Zero, we need to continuously evolve the models we use to understand greenhouse gas sources and sinks. This study looks at the effects of trees, shrubs and lawns on CO2 emissions:

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.

Source: Study: Urban Greenery Plays a Surprising Role in Greenhouse Gas Emissions