Mangrove forests are highly productive ecosystems that provide an invaluable service to humans. In particular they are known to sequester a significant amount of carbon, exceeding the rates of other tropical forests. However, little information is available about the effects of urbanization on mangrove systems and their ability to sequester carbon.
To better understand the effects of urbanization on mangrove ecosystems, scientists with the Environmental Protection Agency and partners studied five mangrove sites along the San Juan Bay Estuary—a highly urbanized area of Puerto Rico with extensive mangrove tracts—to measure carbon dioxide and methane off-gassing at each location. The team used 2-meter C-CAP high-resolution land cover data to identify developed areas, and areas covered by vegetation and open water. In addition, the team used data from other sources to determine mangrove coverage, population density, and road density. A combination of these spatial variables was used to calculate a Mangrove Urban Index. The team measured various components of gas fluxes, soil, and water at all five locations.
The team found that mangroves at the more highly urbanized location experienced higher emissions of carbon dioxide and methane from the soils and adjacent waters. Furthermore, research findings indicate that the more highly urbanized mangrove sites had a higher magnitude of methane emissions in the adjacent waters than the soils. Additional research may be needed to determine if urbanization alters long-term carbon sequestration. (2020)