Mangroves

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Abstract

Mangroves are unique coastal ecosystems distributed almost exclusively in subtropical and tropical regions. Mangroves are important as they sequester more carbon per unit than any other ecosystem and serve to enrich and nurture coastal biodiversity. As such, they play a crucial role in climate change mitigation and contribute to biodiversity conservation. However, in recent years, these ecosystems have been significantly damaged and degraded, thus resulting in the loss of carbon sequestration capacity and the release of blue carbon into the atmosphere, further increasing the levels of carbon emissions into the atmosphere.

Introduction

Mangroves are unique woody plants that occupy the interface between land and sea. As these plants grow in tropical and subtropical regions, they are predominantly found in Southeast Asia, Africa, and South America. Mangroves are especially important as they provide unique ecosystem services such as mitigating climate change. Mangroves sequester more carbon per unit than any other forest ecosystem, thus significantly reducing the amounts of carbon dioxide in the atmosphere (Donato et al., 2011). The carbon sequestered is stored in their soils as blue carbon, creating a unique environment in which specific animal and plant species thrive. Besides mitigating climate change, mangroves also provide environmental regulating services such as land stabilization, coastline protection, and water quality maintenance (Koh et al., 2013). In addition to these environmental services, Mangroves also provide cultural and provisional services such as fuel source and construction materials among others. It ensures populations reliant on this ecosystem have a steady source of resources and income.

Despite their significance, these ecosystems have been slowly degraded through direct and indirect human activities. It has resulted in significant ecosystem damage, loss of habitat for species dependent on this ecosystem, and significant adverse impacts on carbon sink capacity (Carugati et al., 2018). Deforestation poses the biggest threat to these ecosystems as forested mangrove regions have been cleared to pave the way for infrastructure development, urbanization and aquaculture and agriculture activities. Other factors that have significantly degraded these regions include increased human population, local exploitation, uncontrolled coastal development, and gas and oil exploration pollution. Other threats to mangrove ecosystems include climate change and rising sea levels.

This paper aims to highlight the role mangroves play in the carbon cycle and understand how they are being harmed. As previously stated, mangroves are effective carbon sinks as they sequester carbon dioxide and store them in soil sediments and their biomass. This form of stored carbon is known as blue carbon and is beneficial in ecological roles such as transferring nutrients across this unique ecosystem (Macreadie et al., 2019). Besides storing blue carbon, mangroves are also important in the carbon cycle as they export dissolved organic carbon. The destruction of mangroves is therefore disadvantageous as it directly affects organic carbon pools. Disruptions in the organic carbon pools negatively affects atmospheric composition. Moreover, mangroves provide a wide range of environmental benefits and services; as such, there is a need for relevant shareholders to come up with laws and practices that better preserve this unique ecosystem.

How Mangroves Are Being Harmed in Different Regions

The highest diversity of mangroves in the world is found in Southeast Asia. This region has approximately 6.1 million hectares of mangroves, accounting for close to 35% of the world’s mangrove vegetation (Suratman, 2008). Despite the extensive diversity of mangroves in Southeast Asia, the greatest threat to Mangrove ecosystems in the region is deforestation. Countries in this region have lost between 20% to 85% of their mangrove cover in the last 70 years. For instance, between 1976 to 1991, Thailand lost 65% of its Mangrove cover to deforestation. Equally, countries such as the Philippines, Brunei, Indonesia, and Malaysia lost significant potions of their Mangrove forests to deforestation (Suratman, 2008). In recent years, the decrease in mangrove forest cover in this region is attributed to increased seaport infrastructure, land development, and the prominence of agricultural activities such as shrimp farming. With added pressure for economic growth in the region, it is estimated that the region will continue to experience a significant reduction of mangrove ecosystems.

Africa has the second-highest cover of mangroves; however, its diversity formation is low. Mangrove ecosystems in the region are prominent in central and west African countries such as Gabon, Cameroon, Congo, and Nigeria. A mangrove area change analysis carried out between 2000 and 2010 found that the average deforestation rate in this region was approximately 1.8% per year. This average represented an individualized loss of 6% to 35% when broken down. For instance, the Republic of Congo experienced a 35% loss of mangrove cover; Cameroon had an 18% loss while Gabon had a 19% loss of mangrove cover (Ajonina, 2014). Also, a study done in Nigeria’s Niger delta found that between 2007 and 2017, the region experienced a 12% loss of mangrove forest cover (Nwobi, 2017). The biggest threat to mangrove ecosystems in the region is deforestation due to oil exploration, expansion of urban areas, increased agricultural activities such as palm plantations, and the over-exploitation of mangrove wood and non-wood products. Moreover, people in this region significantly rely on mangroves as timber and fuel.

In South America, the most extensive mangrove forest cover is in Brazil. Degradation of mangrove forest covers in the region range from moderate to severe, with regions with the highest populations experiencing severe loss of mangrove cover. It is estimated that 40% of people in Brazil live in coastal regions; thus, mangrove degradation in these regions is severe. Moreover, 42% of the country’s population lives in the country’s southeast region; hence, this region experiences significant deforestation fueled by factors such as urbanization, pollution, and infrastructure development (Ferreira, 2016). Other factors that have resulted in the loss of mangrove cover in the region include the prominence of aquaculture activities such as shrimp farming.

How The Carbon Cycle Is Affected

Mangroves are made up of complex structures that enable them to sequester carbon dioxide and store them in their biomass and soil sediments. As such, mangroves store up to 20pg of carbon dioxide, with 75% of this figure stored in the soil while 25% is distributed between their below and above ground biomass (Donato et al., 2011). As such, the destruction and deforestation of this ecosystem will directly affect the carbon cycle since the oxidation of blue carbon will directly result in a significant release of the carbon dioxide stored in soil sediments and biomass (Sippo, 2020). The release of carbon dioxide will not only increase the amounts of greenhouses gases in the atmosphere, but it will also increase the rates of climate change.

The destruction of mangroves adversely affects the natural distribution of organic carbon pools. The most vulnerable carbon pools include the soil carbons present at 30cm from the top and the above-ground carbon (Donato et al., 2011). The disruption and release of carbon gases from these natural pools are especially disadvantageous as, with time, it can affect the natural atmospheric composition. Other than the potential for carbon emission, the destruction of mangroves can also result in the loss of above-ground biomass. During their growth, mangroves convert carbon dioxide into biomass. When mangrove forested areas are destroyed, it results in the loss of biomass that then increases the amount of carbon gases released into the atmosphere (Alongi, 2020). An increase in the amount of carbon dioxide gases in the atmosphere results I climate change.

Conclusion

Mangroves provide various benefits such as environmental, cultural, and provisional services. These services encompass benefits such as mitigation of climate change, land stabilization, coastline protection, and enhancement of water quality, among others. There is a need for relevant shareholders to increase their efforts to protect such a beneficial ecosystem. Moreover, the leading cause of mangrove degradation is direct and indirect human activities; hence, there is a need for laws and practices that protect mangrove forest zones from economic development and urbanization. Lastly, governments and relevant institutions should develop conservation laws that encourage communities reliant on this ecosystem to use its resources sustainably.

References

Ajonina, G., Kairo, J. G., Grimsditch, G., Sembres, T., Chuyong, G., Mibog, D. E., & Marine, K. (2014). Carbon pools and multiple benefits of mangroves in Central Africa: assessment for REDD+.

Alongi, D. M. (2020). Global significance of mangrove blue carbon in climate change mitigation. Sci, 2(3), 67.

Carugati, L., Gatto, B., Rastelli, E., Lo Martire, M., Coral, C., Greco, S., & Danovaro, R. (2018). Impact of mangrove forests degradation on biodiversity and ecosystem functioning. Scientific reports, 8(1), 1-11.

Donato, D. C., Kauffman, J. B., Murdiyarso, D., Kurnianto, S., Stidham, M., & Kanninen, M. (2011). Mangroves are among the most carbon-rich forests in the tropics. Nature Geoscience, 4(5), 293-297.

Ferreira, A. C., & Lacerda, L. D. (2016). Degradation and conservation of Brazilian mangroves, status, and perspectives. Ocean & Coastal Management, 125, 38-46.

Koh, L. P., Kettle, C. J., Sheil, D., Lee, T. M., Giam, X., Gibson, L., & Clements, G. R. (2013). Biodiversity state and trends in Southeast Asia. In Encyclopedia of Biodiversity: Second Edition (pp. 509-527). Elsevier Inc.

Macreadie, P. I., Anton, A., Raven, J. A., Beaumont, N., Connolly, R. M., Friess, D. A., & Duarte, C. M. (2019). The future of Blue Carbon science. Nature communications, 10(1), 1-13.

Nwobi, C., Williams, M., & Mitchard, E. T. (2020). Rapid Mangrove Forest Loss and Nipa Palm Expansion in the Niger Delta, 2007–2017. Remote Sensing, 12(14), 2344.

Sippo, J. Z., Sanders, C. J., Santos, I. R., Jeffrey, L. C., Call, M., Harada, Y., & Maher, D. T. (2020). Coastal carbon cycle changes following mangrove loss. Limnology and Oceanography, 65(11), 2642-2656.

Suratman, M. N. (2008). Carbon sequestration potential of mangroves in Southeast Asia In Managing forest ecosystems: The challenge of climate change (pp. 297-315). Springer, Dordrecht.

Figure

Global Distribution of mangrove cover.