July 26 is International Day for the Conservation of the Mangrove Ecosystem – a global initiative by Unesco to highlight the importance of mangroves to our planet and call attention to their alarming decline.
Mangrove forests are some of the most valuable ecosystems on Earth. The unique biology of these shrubs and trees allows them to flourish in soil that is low in oxygen and high in salt – conditions that many other plants find toxic.
Although they are found in 123 nations and territories, including Hong Kong and many nations in Asia-Pacific, mangrove forests are globally rare. They represent less than 1 per cent of all tropical forests worldwide, and less than 0.4 per cent of total global forest cover.
Dr Siti Maryam Yaakub is head of ecological habitats and processes at DHI in Singapore, and specialises in tropical coastal and marine habitats including mangroves and seagrass. “It is important to have global awareness events like these because mangroves are very important ecosystems, but they are often underappreciated,” says Yaakub.
“Global trends indicate that mangrove habitats are being lost through coastal development, habitat degradation, pollution and conversion to aquaculture ponds. This loss is especially acute in Southeast Asia.”
Existing at the boundary of land and ocean, these spectacular ecosystems support a rich tranche of animal life – providing a valuable habitat for fish and crustaceans; a food source for monkeys, birds, deer, honeybees and even kangaroos.
“Mangroves trap massive amounts of carbon from the atmosphere, and are therefore very important in the fight against climate change,” says Yaakub. “They’re more effective carbon sinks than terrestrial forest habitats.”
Indeed, mangroves absorb and sequester up to five times more atmospheric carbon dioxide per acre than other tropical forests. One hectare of mangrove can store 3,754 tonnes of carbon; the equivalent of keeping 2,650 cars off the road for one year.
“They’re also great at protecting shorelines and in food production by supporting fisheries,” adds Yaakub. Those mud crabs that you like to eat? They’re found in mangrove habitats.”
Coastal communities around the world rely on mangroves for flood protection, food security, employment and recreation. Mangroves act as a natural defence against erosion, rising sea levels and storm surges. A 500-metre mangrove strip can reduce wave heights by 50 to 99 per cent, and the flood protection benefits of mangroves are estimated to be worth US$65 billion per year.
Yet mangroves are being damaged at an alarming rate. In the last four decades, factors such as habitat loss, over-harvesting, climate change and coastal development have caused the loss of around half of the world’s mangrove forests, causing severe ecological and socio-economic impacts. Mangroves are vanishing three to five times faster than overall global forest losses, and are now among the planet’s most threatened ecosystems.
“Let us take action. Despite their immense importance to our own wellbeing, there is still a lot to do in order to stop the continuous loss of mangrove habitats,” said Shamila Nair-Bedouelle, Unesco assistant director-general for natural sciences, in a statement to mark International Day for the Conservation of the Mangrove Ecosystem 2020.
“Based on science, with the support of environmental education and community involvement, we must conserve, restore and promote the sustainable use of mangrove ecosystems. Strengthening coastal Unesco Biosphere Reserves and establishing new ones is a way to keep what we have and restore what we have lost.”
While the long-term outlook for many mangrove ecosystems is already bleak, positive steps are being taken by governments around the world. Through a greater understanding of the multitude of benefits – both socio-economic and ecological – that mangroves can offer, there is hope that better policies can put a halt to their dramatic decline.