Caldeira Lab

Avoiding Mangrove Destruction By Avoiding Carbon Dioxide

Ken Caldeira


Caldeira, K., 2012a: Avoiding mangrove destruction by avoiding carbon dioxide emissions. Proceedings of the National Academy of Sciences, 109, 14287–14288, doi:10.1073/pnas.1211718109.





Tens of millions of tons of CO2 emissions from mangrove deforestation may be avoided each year at an average cost of less than $10 per ton CO2, conclude Siikamäki et al. in their study (1) in PNAS. Avoiding CO2emission from mangroves would have the beneficial side effect of protecting biodiversity. With careful selection of areas to be protected, increased protection of biodiversity could be obtained at relatively little additional cost. However, a major challenge to mangrove protection is the availability of good governance. It is one thing to pay for mangrove protection and another thing entirely for those mangroves to be protected in practice.

Mangrove forests are found in tropical and subtropical coastal areas throughout the world. Approximately 30% to 50% of mangrove forests have already been lost globally, primarily as a result of coastal development and overharvesting (2). The study of Siikamäki et al. (1) is directly relevant to those interested in developing practical approaches to protect mangroves. However, it raises important issues about the value of CO2emissions avoidance, environmental protection, and good governance.

Siikamäki et al. (1) find that mangroves are among the most carbon-rich of tropical forest, storing on average ∼50 kg C⋅m−2, mostly in soils. Mangroves typically accumulate carbon at a rate of approximately 0.1 kg⋅m−2⋅y−1 (3). Because they cover less than 0.03% of Earth’s surface, despite large fluxes and amounts stored on a per-unit-area basis, they play a relatively small role in the global carbon cycle, taking up approximately 0.06 gigatons (Gt) CO2 annually from the atmosphere. Total carbon storage in mangroves globally could be as much as 20 Gt of C (2), or the equivalent of approximately 2 y of total global anthropogenic carbon emissions (4). Siikamäki et al. (1) estimate …