Quantifying net loss of global mangrove carbon stocks from 20 years of land cover change

Daniel R Richards,Lahiru Wijedasa,Benjamin S Thompson

doi:10.1038/s41467-020-18118-z

Daniel R Richards, Lahiru Wijedasa + Show 1 more

Open Access

https://doi.org/10.1038/s41467-020-18118-z

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Abstract

Mangrove forests hold some of the highest densities of carbon recorded in any ecosystem, but have experienced widespread deforestation through conversion to aquaculture and agriculture. Alongside deforestation, mangroves have shown simultaneous natural expansion in some parts of the world, and considerable investments have been made into restoration programmes. Here we estimate net changes in the global mangrove carbon stock due to land cover change between 1996 and 2016, using data on mangrove deforestation and forestation, and proportional changes in carbon stock during processes of mangrove loss and gain. The global mangrove carbon stock declined by 158.4 Mt (95% CI = −156.8–525.9 Mt); a reduction of 1.8% of the stock present in 1996. Efforts to conserve and restore mangroves appear to have had some success, and - along with natural forestation - have contributed to relatively low net losses of mangrove carbon stocks over two decades.

Highlights

Mangrove forests hold some of the highest densities of carbon recorded in any ecosystem, but have experienced widespread deforestation through conversion to aquaculture and agriculture
We quantified net changes in the global mangrove carbon stock between 1996 and 2016, by combining recently-released datasets describing mangrove forest extent in 1996 and 201614–17, the proportion of carbon stocks lost after conversion from mangroves to other land cover types[13], and the rate of accumulation of carbon stocks during forestation[18]
We quantified the carbon at risk of loss due to land cover change (LCC) (D), the amount of carbon that may eventually be present in the area of forested mangrove (F), the proportion of carbon lost from the system given the time since deforestation, and the proportion of carbon accumulated by foresting mangrove given the time since forestation

Summary

Results

Global net loss of mangrove carbon stocks. The total area of mangrove in 1996 was 142,865 km[2], and the area in 2016 was 136,717 km[2 17]. Without accounting for carbon loss and gain rates, the net loss of mangrove carbon stocks (D − F) was 344.3 Mt (95% CI: 9.0–711.6 Mt; Fig. 1). After accounting for carbon loss and gain rates over time, the carbon stock loss due to deforestation between 1996 and 2016 (Drt) was 232.6 Mt (95% CI: 24.0–537.0 Mt), and gain due to forestation (Fat) was 74.2 Mt (95% CI: 11.0–180.8 Mt). The net loss in global mangrove carbon stock (Drt − Fat) was 158.4 Mt (95% CI: −156.8 to 525.9 Mt; Fig. 1). This estimated net loss of carbon stock is equivalent to. The lower confidence interval for Drt − Fat was negative, indicating a possible net gain in mangrove carbon stocks over the study period (Fig. 1). There were high net losses of mangrove carbon localised to parts of Mexico, Borneo, and Papua (Fig. 3a, b), and net gains in part of Mexico and Myanmar (Fig. 3a)

Discussion

Methods

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