Across cultures, across centuries, mangroves have been perceived as the ethereal roots of the sea. The small trees and shrubs date back to prehistoric times and are present in two realms at once, conglomerating and thriving in swampy lagoons on the boundary of land and sea. They are thought to have originated in Asia, before being dispersed by the ocean and taking root around the world. There are around 80 described species globally, but Southeast Asia houses the greatest diversity. Maybe you have spotted these mysterious mangroves on the shoreline? Were you struck by the tangled maze of twisted roots?
Mangroves exhibit a condition known as vivipary, meaning that their seeds are able to germinate while attached to the parent tree. The seeds either drop below the parent plant or are carried away by the tide, before imbedding into the mud just deep enough so they don’t wash away. The fine estuary silt they are implanted in squeezes out oxygen, so their vertical roots can’t run deep. Instead they lay down aerial roots that intertwine to form a mesh of support for the plant, trapping sediments and accumulating mud, so the mangroves can expand rapidly, onwards and outwards. These aerial roots take on a variety of forms: from bizarre prop roots resembling head massaging devices, to stilt roots like tent guy lines extending away from the main trunk, to large buttress roots that provide mechanical support – they all stabilise the shallow root system in soft, loose soil.
Their speedy growth is all the more astonishing considering the vast array of challenges they face. The twice daily onslaught of tidal flooding brings in water 100 times saltier than most plants could tolerate. Coping mechanisms amongst species include root membranes that prevent salt from entering, special leaf glands that actively secrete the salt, or concentrating the salt in older leaves or bark that can then be shed. To combat the oxygen-poor waterlogged soils, some species have pneumatophores, or pencil roots, that extend from the underground roots to above the soil surface. During low tides, lenticels (aerating pores) on the surface of these pneumatophores allow for gas exchange between the atmosphere and the root’s insides. And of course, most other plants could – quite literally – not stand the desiccating heat of their tropical climes.
By overcoming these obstacles, within a decade the journey of a single seed can spawn a whole biodiverse, interconnected, vibrant and enormously complex ecosystem. Barnacles, mussels, oysters, sharks, jellyfish and shoals of fish encircle their roots. Mudskippers vanish into the oozing mud, monitor lizards squelch, while fiddler crabs survey their hunting grounds. Life is rich in the underworld. An entirely different world is created in the distinctive trees that rise from below. Birds nest in their canopies. People harvest fruits and medicinal herbs. Monkeys swing between branches. A true haven for a myriad of organisms, mangrove forests also provide favourable conditions for other plants to blossom in their midst. Life bursts forth between the relentless ebb and flow of the tides.
The richness of the ecosystem begets a bounty of benefits and uses for both humans and the environment. Fisheries in their vicinity provide a vital food source for thousands. A multitude of forest products can be harvested, such as construction wood, tannins, fuelwood and medicines. The countless organisms they attract enhance local tourism industries. For years they have also held an important spiritual function in different communities, such as the Indonesian Asmat people who believe their God created man out of mangrove wood. They also provide storm protection for the coastal regions they stabilise. In fact, it is believed that more mangroves acting as a barrier could have reduced the devastating impacts of the 2004 Asian tsunami. Crucially, when compared to most other ecosystems globally, mangroves can store substantially higher densities of carbon. This means they can soak up more of the carbon dioxide in our atmosphere, thereby acting as our natural allies against climate change. In total, scientists peg the monetary worth of the world’s mangroves at US $194,000 per hectare per year. Perhaps money really does grow on trees.
However, these forests are being destroyed daily. Increased global demand for commodities spells trouble for Southeast Asian mangroves that have already experienced extensive deforestation over the last few decades. Agricultural expansion for rice continues in Myanmar and mangroves are being converted to oil palm plantations in Malaysia. Nearly ¾ of Indonesia’s mangrove forests have been damaged. If inland forests are degraded, sediment quality is reduced, and less organic matter is available for mangroves to flourish. For instance, in the Chao Phraya River Delta in Thailand, an 80% reduction in the sediment supply, coupled with an increase in groundwater pumping, has resulted in many kilometres of mangrove shoreline retreat. Land reclamation has contributed to Singapore’s mangrove area being reduced to less than 5% of the original habitat. The largest remaining patch at Sungei Buloh Nature Reserve is now under legal protection.
Shrimp farming wreaks havoc on local fisheries and aquaculture, as well as devastating the mangroves cleared to make way for farms to feed our voracious appetites. These farms are typically abandoned after a few cycles to prevent disease outbreak, before yet another mangrove patch must fall by the wayside. Oh and remember the inbuilt carbon storage facility in mangroves that we mentioned earlier? Converting mangrove areas to shrimp farms can release this CO2 back into the atmosphere 50 times faster than if the mangrove was left undisturbed. Then there are insect pests, genetic disconnection from other mangrove patches, illegal agricultural activities, trespassing, the fact that mangroves will be the first to face rising tides… the list goes on. If we continue marching down this path, it could lead to the disappearance of mangroves before the next century. After all, they are infinitely adaptable until they are not. Chaos often ensues when things get uprooted.
The statistics are harrowing and can induce doom, gloom and despair. However a glimmer of hope beckons beyond the trail of destruction. Recognising the role of mangroves in the fight against climate change, Sri Lanka has now become the first nation to protect all of its mangroves and include mangrove forest conservation in its national curriculum. Malaysia contains the Matang mangrove forest; the longest managed mangrove forest in the world and the only site that practices sustainable wood production. It could be exemplary to other mangrove areas for their management.
Nevertheless, factors as contentious and complex as the tangle of roots create confusion over exactly who is responsible for what. Should mangroves be managed as terrestrial forest or wetlands or fisheries or something else? It never was easy to be in two places at once. Stronger incorporation of mangroves into marine protected areas could ensure that mangroves do not fall through the policy gap, as well as strengthening the relationship between policy and action.
Also helping to strengthen this relationship are grassroots level projects, like the Mangrove Action Project, and a variety of local initiatives emerging to protect and restore mangroves. Imperatively, these endeavours also generate much needed awareness amongst key stakeholders and the general public, who have become increasingly disconnected from the ways in which mangroves can enhance our natural environment. Restoration is difficult and while rehabilitation is possible it may not always be successful; there is often a discrepancy between the aims of restoration and the reality on the ground. It is not too late to turn the tide on mangrove loss, but local governments, communities, NGOs and charities must cooperate and work together towards solutions.
Mangroves are the link and stability maintainer between ecosystems, provide vital protection for our shorelines, nurture a diversity of marine life and have played a vital part in coastal communities for centuries. Millions of people in these communities today still depend on the services that mangroves provide. While human-environment interactions change over time, without integrating and understanding their influence and importance in our past, we lose the potential to see them as a key to the success of our region’s future. Mangroves are one of the most important ecosystems on the planet and their loss would have a profound impact on Asia for years to come.
It would seem that these roots run deep after all.