The Impending Climate Time Bomb Disguised As A Carbon Sink
The Impending Climate Time Bomb Disguised As A Carbon Sink
Mangroves could have devastating climate implications, thanks to humanity.
Nature has a tendency to solve our problems better than we ever can. One brilliant example of this is mangroves. These trees grow on muddy tidal flats and are not only vital for the health of the ocean but also create one of the most prolific carbon sink ecosystems on the planet. The deep oxygen-free salty mud they amass and trap with their aerial roots stores carbon ten times faster than a mature rainforest. In fact, worldwide mangroves store carbon equivalent to 36.6 billion tonnes of carbon dioxide! As such, it’s no wonder there have been significant efforts to expand mangrove forests in an attempt to offset our climate crimes. However, a new study has found this carbon sink is far from secure and might actually be a climate time bomb primed to go off by the end of the century.
The urgency of the mangrove loss issue cannot be overstated. Despite the existence of a thriving carbon credit market that pays for the protection and expansion of mangroves, we are still witnessing a rapid decline. Between 2010 and 2020, we lost an average of 21,200 hectares of mangroves annually. While this is a decrease from previous decades, thanks to conservation and carbon credits, it is still a significant loss. This is especially alarming when considering the carbon stores. A single hectare of mature mangrove forest stores 840 kg of carbon, equivalent to 3,080 kg of carbon dioxide, in its anaerobic mud. However, as mangroves die back, the soils loosen and become aerated, allowing microbes to break down the carbon compounds within the mud. This releases the carbon back into the atmosphere in the form of methane, a greenhouse gas 28 times more potent than carbon dioxide, and a small amount of carbon dioxide.
But, if our current efforts are reducing the annual loss of mangroves, surely this problem will solve itself.
Well, not according to a recent study.
This study examined how human population density affects soil carbon stocks in urban mangrove forests. After combing through reams of data, the researchers found that when human population density near a mangrove reaches 300 per km², which is considered urban, the carbon stored in the mangrove soil is reduced by 37%.
This wouldn’t be a problem if it weren’t for the fact that human populations near mangroves are set to explode by the end of the century.
The researchers found that current mangrove loss causes only 7 million tonnes of carbon to be released into the atmosphere yearly. However, by 2100, increased population density will push this figure up to 3.4 billion tonnes! Again, most of this will be released in the form of methane, meaning it will have roughly the same climate impact as 128 billion tonnes of carbon dioxide. Needless to say, that is enough to make climate change significantly worse.
Despite the challenges, there is hope for mangroves. The researchers discovered something intriguing when they delved into their data. The negative correlation between population density and mangrove soil carbon was significantly diminished when they factored in climatic conditions and other factors. In some models, it even became “non-significant”. This essentially means that mangrove ecosystems in close proximity to very high population density can still possess valuable carbon stocks if adequately protected. While there is still much to learn about what ‘adequately protected’ entails, this research demonstrates that we have the potential to prevent this ticking climate time bomb from detonating and preserving one of the planet’s largest and most productive carbon sinks.
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Sources: IOP, Scietechdaily, Global Mangrove Alliance, More Trees, CIFOR, NOAA, EPA, Mongabay, Worldometers