Global economic potential for reducing carbon dioxide emissions from mangrove loss

Abstract

Mangroves are among the most threatened and rapidly disappearing natural environments worldwide. In addition to supporting a wide range of other ecological and economic functions, mangroves store considerable carbon. Here, we consider the global economic potential for protecting mangroves based exclusively on their carbon. We develop unique high-resolution global estimates (5' grid, about 9 × 9 km) of the projected carbon emissions from mangrove loss and the cost of avoiding the emissions. Using these spatial estimates, we derive global and regional supply curves (marginal cost curves) for avoided emissions. Under a broad range of assumptions, we find that the majority of potential emissions from mangroves could be avoided at less than $10 per ton of CO(2). Given the recent range of market price for carbon offsets and the cost of reducing emissions from other sources, this finding suggests that protecting mangroves for their carbon is an economically viable proposition. Political-economy considerations related to the ability of doing business in developing countries, however, can severely limit the supply of offsets and increases their price per ton. We also find that although a carbon-focused conservation strategy does not automatically target areas most valuable for biodiversity, implementing a biodiversity-focused strategy would only slightly increase the costs.

Fig. 1.

A global map of mangroves and their division into three geographic regions. Compiled using data from Giri et al. (10).

Fig. 2.

Global and regional supply curves for emissions reductions from mangroves using low, central, and high estimates of avoided emissions. Supply curves were constructed by identifying the least-cost configuration of protections to generate different amounts of avoided carbon emissions, ranging from zero to total emissions avoided from new protections equal in area to projected annual mangrove loss (Methods).

Fig. 3.

Governance and the supply of emissions reduction from mangroves. The supply curves correspond to the central carbon case. The Top 90 line excludes the bottom 10th percentile of countries according to the government effectiveness rankings of the World Bank. The Top 50 line excludes the bottom 50th percentile.

Fig. 4.

Additional cost of using a targeting approach based on cobenefits. Supply curves use the central carbon estimate and were generated in a similar manner to the global and regional curves, except in this case, all mangrove hectares within a cell were assumed to be fully protected and cells were included in the country supply until the country-level deforestation hectares were met. The additional costs to supply different levels of CO₂ were generated by calculating the differences in costs between the targeting approach and the lowest-cost scenario (SI Appendix).