My Mangroves, My Livelihood
The International Day for the Conservation of the Mangrove Ecosystem, adopted by the General Conference of UNESCO in 2015 and celebrated each year on 26 July, aims to raise awareness of the importance of mangrove ecosystems as “a unique, special and vulnerable ecosystem" and to promote solutions for their sustainable management, conservation and uses.
Photo: MESCAL Vanuatu
Mangrove forests are essential and productive ecosystems that provide numerous goods and services to the marine environment and local communities.
Mangroves are trees or shrubs that are found in the intertidal zone of coastlines, or that area between the coastal environment and the terrestrial environment. These florae are well-adapted to living in saline (salty) and brackish environments, which is one of the reasons that they are so unique. There are about 70 species of mangroves found along tropical and sub-tropical coastlines, with a particularly heavy presence in Asia, followed by Africa and South America. The largest area of mangroves are found in Indonesia, followed by Brazil, Australia, Nigeria, and Mexico.
Mangrove trees are equipped with impressive filtration systems that allow them to filter out or exclude salt altogether, despite their twice-daily inundation by saltwater due to changing tides. Perhaps their most notable feature, mangroves have complex root systems that extend above and below the water line. These roots allow mangroves to stabilize themselves and prevent erosion to the coastline, and also provide habitat, nurseries, and feeding grounds for a vast array of fish and other organisms.
Yet mangroves are disappearing three to five times faster than overall global forest losses, with serious ecological and socio-economic impacts. Current estimates indicate that mangrove coverage has been divided by two in the past 40 years.
Mangroves in the Pacific
The world area of mangroves has been recently mapped at 152,000 km2 (Spalding et al., 2010). In the Pacific Islands region, the total mangrove area is nearly 5,687 km2 , or 3.74% of the world’s mangroves, with the largest areas in Papua New Guinea, Solomon Islands, Fiji and New Caledonia.
Mangrove areas in some Pacific Island countries are high relative to their land area, such as 12% of the Federated States of Micronesia, and 10% of Papua New Guinea and Palau.
Pacific Islander societies have traditionally been based in coastal resource management, with many early settlements close to mangrove areas. They continue to provide significant social, economic and cultural benefits for the people of the Pacific Islands, with approximately ten million inhabitants.
In 1987, Woodroffe observed four type of environments of mangroves in the region:
- Deltas and estuaries such as the Fly River Delta in Papua New Guinea and the Rewa Delta in Fiji;
- Intertidal slopes and lagoons as seen in Tongatapu, Tonga;
- Sandy substrates or reef flats in Funafuti, Tuvalu; and
- Inland sink-holes in the islands of Niutao and Nanumanga, Tuvalu.
Mangroves are critical ecosystems for promoting and supporting biodiversity. The unique role of the mangrove forest as the interface between coastal and terrestrial ecosystems enables it to provide a wide array of habitats and thus support a huge diversity of species, including terrestrial, estuarine, and marine organisms. Mangroves support a large number of threatened and endangered species, such as the hawksbill turtle, the Bengal tiger, and several water bird species, for example. Mangroves are also key habitats for many migratory birds that rely on the forests as stop-overs along their migratory paths. It has also been documented that mangroves provide refuge for corals from ocean acidification, thus contributing to the survival of these important species.
In addition to the vast array of life that mangrove forests directly support, they also contribute to the survival of other nearby ecosystems through their sediment trapping and filtration processes. Mangroves therefore indirectly support the species to which these adjacent ecosystems provide a home. It has also been documented that mangroves may provide protection to corals from rising sea temperatures as a result of climate change. Warmer ocean waters can lead to deadly bleaching of corals, which also leads to the death of the organisms that live within and depend upon coral reefs. Mangroves may prove to be very beneficial in protecting coral biodiversity and their dependent species, through the provision of shade and a buffer against rising ocean acidity. Mangroves themselves are also a diverse group of organisms, with approximately 70 species documented worldwide.
Importance of mangrove ecosystem
Mangrove ecosystem are importance because of the following contribution:
Mangroves contribute significantly to the human wellbeing of the coastal communities that they adjoin.
First, mangroves help to provide food security for local communities. Mangroves serve as nurseries for many fish and other marine species, without which many fisheries, including local coastal fisheries as well as commercial coastal and offshore fisheries, would not survive. In fact, it is estimated that “almost 80% of global fish catches are directly or indirectly dependent on mangroves”. Mangroves also provide ideal locations for aquaculture, which is currently “the fastest growing food-producing sector in the world”, though often mangrove forests are destroyed for this purpose. There are movements in place to encourage more sustainable forms of aquaculture that complement the local environment instead of destroying it, but this is still not the norm. In addition to the more traditional fishery products, mangroves contribute to food security through the provision of several other food products, including honey, algae, fruit, salt, and leaves for livestock feed.
In addition to their contribution to food security, mangroves also contribute significantly to local livelihoods, providing employment for a significant coastal population across the globe via the fisheries and tourism that they support. Mangroves also provide valuable timber for firewood and construction in local communities. Mangrove forests also provide water purification services and aid in the detoxification of wastes. Aside from the more tangible benefits of these ecosystems, mangroves offer value that is much less easily quantified, in the form of aesthetics, culture, spirituality, and recreation.
Importantly, mangroves also provide significant buffering against coastal erosion, storm surge, and sea level rise. It is estimated that mangroves help to reduce wave heights by 31%, protecting homes, property, and infrastructure from dangerous flooding. Additionally, these forests serve as incredible carbon storage mechanisms, thereby aiding in the preservation of human wellbeing via climate regulation.
Mangrove forests serve a critical role in climate regulation and climate change mitigation. The trees/shrubs themselves, as well as the soil beneath them, serve as highly effective carbon sinks and storage sites. Mangroves absorb large amounts of carbon dioxide from the atmosphere during photosynthesis and are able to store this carbon, often referred to as “blue carbon,” for extended periods of time, in the plant structure and in the soil beneath them. Blue carbon, the carbon that is captured and stored in coastal ecosystems, can be locked away in the soils beneath mangroves for hundreds to thousands of years, if left undisturbed.
Mangroves are incredibly efficient carbon sinks/stores, absorbing carbon at a much faster rate than terrestrial forests, and locking this carbon away for a much longer period of time. It is estimated that mangroves store 3 to 4 times more carbon than tropical forests. Mangroves store much of their carbon in the soil and in their dead roots.
Notably, “Mangroves account for only approximately 1% (13.5 Gt year-1) of carbon sequestration by the world’s forests, but as coastal habitats they account for 14% of carbon sequestration by the global ocean.”
Mangroves offer significant potential for aiding coastal communities in adapting to climate change. Climate change poses a serious threat to coastal communities and their livelihoods. Sea level rise, coastal erosion (due to storm surge and sea level rise), and more intense and frequent storms and heavy rainfall events are all expected impacts of climate change, and these impacts are already being documented in some areas. As these threats are looming, coastal populations are also expanding, and much of this growth is taking place in highly impoverished tropical nations. As coastal vulnerability increases, it is crucial that climate adaptation and risk reduction measures be put in place. Mangroves may play an important role in climate adaptation in coastal communities.
Mangrove forests offer significant protection from coastal erosion, storm surge, and sea level rise, all of which may lead to potentially devastating and life-threatening flooding along the coast. Mangroves are already being utilized in some ecosystem-based adaptation (EBA) projects, which seek to use nature to promote resilience to climate impacts. The restoration of mangrove forests in vulnerable areas can help to provide protection against climate threats, and can bolster food and livelihood security, both of which are threatened by climate change.
Mangrove forests provide a wide range of ecosystem services to Pacific Island communities. It is a source of plant and animal foods, timber, medicine, and canoe logs. This is because mangroves are hotspots of biodiversity. They form a rich and productive habitat by providing a nursery, home, and feeding ground to many fish, insects, and birds. Additionally, mangroves are important in climate change mitigation and adaptation strategy. In some areas, mangroves are the natural line of defence from storm surges and flooding. They also help prevent coastal erosion, facilitate the transfer of energy and nutrients from land to sea, and have the ability to store carbon dioxide (Baines, 1981).
Threats to the mangrove ecosystem
Mangroves are disappearing at an alarming rate with serious ecological and socio-economic impacts. According to a study by Cameron et al. (2021), the greatest drivers of mangrove loss are increasing frequency and intensity of natural disasters such as tropical cyclones and flooding, coastal reclamation for unsustainable aquaculture and infrastructure development, and overexploitation of mangrove resources.
In the latest report by the Global Mangrove Alliance, an estimated 67% of mangroves have been lost or degraded, and an additional 1% is lost each year putting mangroves at the risk of being destroyed completely. IUCN, World Wildlife Fund, The Nature Conservancy, Conservation International, and Wetlands International form the Global Mangrove Alliance. The Alliance brings together local communities, Non-government organisations, governments, industries, and funders to not only halt mangrove degradation, but also increase mangrove cover by 20% by 2030 as highlighted in the newly launched UN Decade of Ecosystem Restoration.
More people are living along coasts than ever before and consequently pollution runoff has risen, threatening nearby mangroves which act as natural filters of runoff to the ocean. Pollution may come from sources like urban runoff, agriculture and oil spills and can interfere with the exchange between mangrove roots and the atmosphere and soil. Oil can, for example, suffocate mangroves by coating their roots.
An overabundance of nutrients like potassium and nitrogen from urban runoff can disturb mangrove growth. In Mumbai, high concentrations of lead, mercury and chromium have been found, in addition to debris dumping and untreated sewage water. The pollution load varies for different mangrove forests as well as among species. For example, Avicinnea is one of the most tolerant species to heavy metals. In India, the A. marina has increased in numbers, likely due to its resistance to pollution, thus causing a decline in biodiversity.’
Salinity and Sedimentation
Dams, irrigation and other alterations to landscape can alter the water, salinity and sedimentation levels of mangrove ecosystems which can contribute to mangrove decline. A new causeway, for example, may impede the tide coming into the mangroves, lowering the fresh to saltwater balance of the estuary. On the other hand, irrigation or a newly constructed dam may alter freshwater flow into the mangroves, increasing its salinity.
While mangroves have various adaptation techniques to deal with salinity, such as filtering at the root level or storing excess salt in leaves and shedding them, high salinity can cause dehydration, imbalances in nutrition and changes in iron levels that can negatively impact mangroves.
Mangroves are also indirectly affected by the agriculture industry, affected by the chemicals and fertilizers used in on plantations that runoff into the environment. In addition, water may be diverted for crops, through dams and irrigation, which may change the salinity or amount of water in mangrove habitats.
One of the biggest threats to remaining mangrove forests is coastal development. As coastal populations continue to grow and coastal tourism increases, mangroves are cleared to make way for infrastructure, businesses, hotels, and homes. Development in the coastal zone also leads to mangrove destruction indirectly through the increased pollution, altered hydrology, and harmful human contact that can result. Additionally, coastal development too close to mangrove habitat can limit their ability to migrate landward as sea levels rise, diminishing their resilience and therefore the resilience of the communities that they protect. Ironically, destruction of mangroves for development puts the new construction at even higher risk to damage from storms, leading to increased economic losses.
Coastal development can be sustainable, however, if it is well-planned, innovative, and integrates the surrounding ecosystems, livelihoods, and needs of all stakeholders. Ecotourism and integrated coastal zone management offer promising opportunities for future development.
At first glance, the twisted roots and swamp-like environment of the mangrove forest may not appear to be one of abundance, but, in fact, mangroves are one of the most biodiverse, valuable ecosystems on the planet. These productive ecosystems serve as valuable resources for coastal communities, providing sources of food, medicine, firewood, and income. However, as with any natural resource, mangroves are at high risk from unsustainable practices, including overfishing and over-harvesting, both of which are leading to their destruction and degradation across the globe. Why are mangrove resources being exploited? There are several reasons, which include an ever-increasing global and coastal population which creates higher demand, an increase in poverty levels, globalization of industry (which means that locals must compete with commercial demands for the same resources), and increased coastal tourists.
Protection of Mangroves
Mangroves are recognised as the most productive nature-based solution due to the goods and services it provides yearly. Action must be taken to protect and properly manage our mangrove ecosystem.
Interventions such as incentives to help reduce emissions and encourage mangrove afforestation. It is crucial that management plans include stakeholders and beneficiaries in order to successfully plan and implement appropriate regulations, policies, and national laws for the sustainable use and conservation of mangroves.
Halting mangrove loss It is essential to prevent further mangrove loss, degradation, and fragmentation to ensure the persistence of healthy, intact mangrove ecosystems and the ecosystem services they provide.
Now is the time to build on the global momentum and secure what remains of the world’s mangroves. Implementing science-based restoration Large-scale mangrove restoration with communities and stakeholder engagement and participation, based on sound science.
What Can You Do To Help?
1. Plant your own mangrove tree
Each mangrove planted will:
- Provide nursery ground for species
- Help the coasts from storm-surges and sea-level rise
- Create a habitat for threatened species
- Sequester CO2 and help reduce global heating
2. Use Your Voice
Mangrove forests are 5x more effective at storing carbon than tropical rain forests and without them, CO2 levels and global heating will continue to rise. Fast.
Help educate others by sharing this blog with your friends, family and the rest of the world.
Global Mangrove Tracking Tool
The Global Mangrove Restoration Tracking Tool attributing to the global objective of increasing the conservation and restoration of mangrove cover, by 20% in 2030.
This month, July, Conservation International, with other Global Mangrove Alliance (GMA) members undertook a part in a series of mangrove restoration virtual workshop organized by Dominic Andradi-Brown (WWF-US) and Tom Worthington (University of Cambridge) on behalf of the GMA Science Working group. The workshops enable stakeholders’ comments on the tracking tool for better utilization by users on the ground.
Baines, G., (1981). Mangrove Resources and Their Management in the South Pacific. South Pacific Regional Environment Programme. South Pacific Commission. Niumea, New Caledonia.
Cameron, C., Maharaj, A., Kennedy, B., Tuiwawa, S., Goldwater, N., Soapi, K., Lovelock, C. (2021). Landcover change in mangroves of Fiji: Implications for climate change mitigation and adaptation in the Pacific. Environmental Challenges 2021. doi:https://doi.org/10.1016/j.envc.2020.100018.
Ellison, J. C. (2000). How South Pacific Mangroves May Respond to Predicted Climate Change and Sea-level Rise. Climate Change in the South Pacific: Impacts and Responses in Australia, New Zealand, and Small Island States, 289–300. doi:10.1007/0-306-47981-8_16.
Woodroffe, C., (1987). Pacific island mangroves: Distribution and environmental settings. Pacific Sci. 41, p.166-185
Alliance, G. M. (2021, July 23/7/2021). Mangroves. Retrieved from Global Mangrove Alliance: www.mangrovealliance.org