Article: Future Carbon Emissions from Global Mangrove Forest Loss by Adame and colleagues (2021)
Background: Many who have visited the tropics and subtropics are familiar with mangroves. These shrubs, whose roots rise out of shallow saltwater, form dense coastal forests across six continents. Mangroves have a great capacity to store excess carbon, helping to mitigate greenhouse gas emissions. However, as global deforestation of mangroves occurs, the mangrove-stored carbon is released into the atmosphere, and the surrounding ecosystem’s ability to store carbon in the future is decimated-- worsening climate change. In order to best manage and protect mangrove forests to mitigate climate change, it is important to know how the loss or disturbance of these ecosystems will affect the global carbon budget. Researchers Adame and colleagues developed a model to predict future global carbon emissions due to mangrove loss.
Methods: The causes of mangrove loss were sorted into five categories: conversion to agriculture or aquaculture (i.e., farming fish or aquatic plants), coastal erosion, clearing due to logging or other activities, extreme climatic events (e.g., tropical storms), and conversion to human settlements. Using satellite imagery, researchers were able to estimate the global extent of mangroves in the year 2000. Then, based on how the satellite imagery has changed over time, they were able to estimate the extent of mangrove loss and attribute the proportions of the loss into each of the five categories. The total amount of carbon stored in mangrove ecosystems, including carbon stored in the actual shrubs and the surrounding soil, was calculated from global data sets. Using predicted future carbon emissions, rates of deforestation, and the amount of carbon stored in mangrove ecosystems, researchers were able to predict future carbon emissions from mangrove loss.
Findings: The conversion of mangrove forests to agriculture/aquaculture systems is the number one driver of mangrove loss; it is responsible for up to 87% of mangrove loss in some global regions. The second most important driver was erosion, followed by extreme climatic events (3rd), mangrove clearing (4th), and human settlement (5th). By 2100, global emissions from mangrove loss are expected to reach 3,392 teragrams (Tg) of CO2, which is about 50% of what the US emitted in 2019 (EPA). This is also equivalent to the annual emissions of 730 million cars.
Conclusions: The loss of mangroves is largely driven by conversion to agricultural land as a result of global demand for products such as rice, palm oil, and rubber. Although mangrove loss is expected to add about 50% of US annual emissions to our global carbon surplus, these emissions can be managed through sustainable agricultural practices and restoration of formerly converted mangrove areas where possible. The second most important driver, erosion, can be managed through shoreline stabilization and removal of dams which block replenishing sediment from reaching coastal areas. These crucial ecosystems can be saved through smart land management, sustainable agriculture, and supporting mangrove conservation efforts.
Figure 1: Global map of (a) projected CO2 emissions (TgCO2, teragrams of CO2) due to mangrove loss and (b) main drivers of mangrove loss in each marine province.
Figure 2: Mangroves (©NuttKomo/Fotolia)
Reference:
Adame, M., Connolly, R., Turschwell, M., Lovelock, C., Fatoyinbo, L., Lagomasino, D., Goldberg, L., Holdorf, J., Friess, D., Sasmito, S., Sanderman, J., Sievers, M., Buelow, C., Kauffman, J., Bryan‐Brown, D. and Brown, C. (2021), Future carbon emissions from global mangrove forest loss. Global Change Biology. Accepted Author Manuscript.
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