By Talia Treble –
Mangrove Forests, as coastal ecosystems, store vast amounts of carbon whilst providing resources and protection for communities stricken by the impacts of climate change [1]. With the importance of storing ‘blue carbon’ [2] becoming increasingly recognised, the destruction of these environments is fast becoming a global environmental challenge.
Figure 1: Mangrove forest near Sabong Beach, Puerto Princesa, Philippines. Source: USAID Biodiversity & Forestry, Public domain, via Wikimedia Commons
Blue Carbon
Blue carbon can be defined as “the carbon stored and sequestered in mangrove forests, seagrass meadows and tidal salt marshes” [3]. These coastal environments offer a cost-effective mitigation strategy for climate change [3], whilst providing vital services to local communities. These include protection from tropical storm events, water quality maintenance, habitat for fisheries and land stabilisation [4]. Mangroves are particularly efficient at storing blue carbon, holding on average 1023 Mg per hectare [5]. It is estimated that the destruction of these forests makes up approximately 10% of emissions from deforestation on a global scale, even though they count for just 0.7% of tropical forest land area [5]. This data highlights the concentration of carbon that can be stored in these ecosystems and therefore the need for them to be protected on a local and global scale.
Mangrove destruction in China
In 2019, a group of scientists and researchers conducted a study into the degradation of mangroves in China [6]. Through extended field investigation and calculations, they recorded the plant species most at risk of extinction and produced numerical data to validate the need to restore them. For example, only one population of 11 individuals of the species L. littorea was found in the June 2019 survey in comparison to the population size of 359 individuals in the study area in 2006 [6]. The areal extent of mangrove forests in China has also decreased by 50% between 1950 and 2001, resulting in an estimated 10.8% decrease in carbon sequestration rate [6]. This continuing decline is decreasing biodiversity and the potential amount of carbon that can be sequestered. When amplified to a global scale, restoring and investing in these ecosystems could mitigate the effects of climate change significantly.
Global relevance
Studies have revealed that over 35% of mangrove forests have been lost worldwide between 1980 and 2000 [8]. There are varying reasons for their decline. For example, in Fiji, the biggest driver of mangrove loss is tropical cyclones, accounting for 77% of the destruction [1]. Due to our current global greenhouse gas emissions, the world temperature is warming resulting in many consequences; one being increased extreme weather events like tropical cyclones. These damage and destroy mangrove forests, reducing the extent of the carbon sink, contributing to greater rates of climate change which will increase storm events. In this way, the global effects of mangrove deforestation and the positive feedback loops involved become clear.
Deforestation, as a global environmental challenge, has gathered momentum in the public eye as an issue that needs to be stopped. Deforestation of mangroves, as a part of this, perhaps deserves wider recognition in both policy discourse and public concern.
References and further reading:
[1]: Cameron, C., Maharaj, A., Kennedy, B., Tuiwawa, S., Goldwater, N., Soapi, K. and Lovelock, C. E. (2021) Landcover change in mangroves of Fiji: Implications for climate change mitigation and adaptation in the Pacific. Environmental Challenges 2, 100018.
[2]: Taillardat, P., Friess, D. and Lupascu, M. (2018) Mangrove blue carbon strategies for climate change mitigation are most effective at the national scale. Biology Letters 14, 1-6.
[3]: Thomas, S. (2014) Blue carbon: Knowledge gaps, critical issues, and novel approaches. Ecological Economics 107, 22-38.
[4]: Grimsditch, G., Alder, J., Nakamura, T., Kenchington, R. and Tamelander, J. (2013) The blue carbon special edition- Introduction and overview. Ocean & Coastal Management 83, 1-4.
[5]: Donato, D., Kauffman, J., Murdiyarso, D., Kurnianto, S., Stidham, M. and Kanninen, M. (2011) Mangroves among the most carbon-rich forests in the tropics. Nature Geoscience 4, 293-297.
[6]: Wang, W., Fu, H., Lee, S., Fan, H. and Wang, M. (2020) Can strict protection stop the decline of mangrove ecosystems in China? From rapid destruction to rampant degradation. Forests 11, 55.
[7]: Jinhong, W (2020) Report of China mangrove conservation and restoration strategy research project. [pdf] Global Mangrove alliance. Available at: https://www.mangrovealliance.org/tools-and-resources/ [accessed 28 November 2021].
[8]: Sanderman, J., Hengl, T., Fiske, G., Solvik, K., Adame, M., Benson, L., Bukoski, J., Carnell, P., Cifuentes-Jara, M., Donato, D., Duncan, C., Eid, E., Ermgassen, Philine., Lewis, C., Macreadie, P., Glass, L., Gress, S., Jardine, S., Jones, T., Nsombo, E., Rahman, M., Sanders, C., Spalding, M. and Landis, E. (2018) A global map of mangrove forest soil carbon at 30m spatial resolution. Environmental Research Letters 13, 1-12.
