Abstract
Mangroves are carbon-rich ecosystems found in tropical and subtropical areas around the world. However, they are threatened by a combination of natural and human-induced factors. When mangroves are lost or degraded, their co-benefits to human society are greatly diminished along with the ecosystem’s ability to sequester carbon. The current study assessed mangrove cover and cover change, as well as measuring carbon stocks and their emissions levels from the mangroves of Lamu County, Kenya. We sampled above-and below-ground carbon pools, including soil organic carbon (SOC), in 191 plots distributed throughout the study area. Lastly, we evaluated the economics of avoiding mangrove deforestation based on the carbon-offset market. The total carbon stock of mangroves in Lamu was estimated at 20 million Mg C, with an average density of 560.22 ± 79.79 Mg C ha–1. Southern swamps recorded significantly higher carbon densities (p < 0.05) than other mangrove management blocks in Lamu. At least 1,739 ha of mangroves in Lamu were lost between 1990 and 2019 due to anthropogenic activities, representing a decline of 60 ha yr–1. Total emissions from loss and degradation of mangroves in Lamu is estimated at 140.1 Mg C ha–1; which translates to 30,840.1 Mg CO2e yr–1. Assuming an offset price of US$10/Mg CO2e, the estimated costs of avoided emissions in Lamu is US$308,401 yr–1 plus other co-benefits such as fishery functions and shoreline protection. Mainstreaming mangroves and associated blue carbon ecosystems into national development and climate change agenda could accelerate Kenya’s achievements of both Sustainable Development Goals (SDGs) and the Paris Agreement.
Highlights
Mangroves and associated coastal wetlands are carbon-rich ecosystems (Donato et al, 2011)
Accuracy levels achieved in mapping overall mangrove coverage was 95% while accuracy achieved in discriminating mangroves by species formation stood at 71.3% registering a Kappa coefficient of 0.6153 (61.5%)
The loss of mangrove in Lamu over the 1990–2019 period contributed to CO2 emissions to the atmosphere amounting to 30,840.1 Mg CO2e yr−1
Summary
Mangroves and associated coastal wetlands are carbon-rich ecosystems (Donato et al, 2011). Despite occupying only 0.7% of the tropical forest area (Giri et al, 2011), mangroves account for about 3–4% of global carbon sequestration by forests (Bhomia et al, 2016; Alongi, 2020) and 10–15% of total carbon sequestration in the coastal ocean (Alongi, 2014). Inclusions of concrete ocean-based mitigations and adaptations actions allow countries to increase ambitions of realizing their NDCs commitments (Taraska, 2018)
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