The Importance of Mangroves

It’s Easter, a time that for many, delivers thoughts of renewal and hope which are much needed when observing today’s news of environmental degradation.

Renewal is the story of a little-known project of mangrove restoration, on the remote Union Island mangroves where restoration involved trial and error to understand how natural systems can restore themselves given the right conditions, time, and stewardship.

In 1994, an ancient mangrove forest on the Caribbean Island of Union was ripped apart for coastal development and ecotourism economical boost. A foreign investor had started the foundation work for a hotel, marina, and golf course in Ashton lagoon on Union Island, but shortly after 4 hectares of mangroves had been ripped out the developer fell short of funds declaring bankruptcy, abandoning the project.

Today however, if you were to visit Union Island, you would come across a thick mangrove canopy which started growing back since 1995, housing three of the world’s 80 mangrove species: the red, which are excluders, and the black and white, which secrete salt. Ashton Lagoon is a critical habitat for many species, birds and fisheries alike, and its Mangroves have continued to provide vital livelihoods to local fishermen. But the road to restoring this mangrove was not without challenges, as many other mangrove restoration projects around the globe have equally faced challenges, including the first ever world bank approved restoration project which failed monumentally, leaving only 18% of the replanted species in tack.

Mangroves are the forests of the sea and amongst the world’s most at-risk ecological systems[1], in places, being razed four times faster than terrestrial forests[2].

They straddle the connection between land and sea, natural and manmade ecosystems. Mangroves nurture estuaries and can support nature-based economies (paid ecosystem services). Their dense root systems help bind and build soils. Their above-ground roots slow down water flow and encourage sediment deposits that reduce coastal erosion. Studies indicate that, pound for pound, mangroves can sequester four times more carbon than rainforests, with most of the carbon stored in the soil beneath the mangrove trees.

Mangroves thrive where most plants cannot. Of the almost 400,000 plant species, only 1,500 are tolerant[3] to saltwater, including 80 mangroves species. Globally mangroves have decreased by over a million hectares (3,860 sq miles)[4] between 1990 and 2020 – an area larger than the island of Puerto Rico. The economic fallout, including the loss of fisheries, has been calculated as greater than $40bn (£30bn) a year[5] and the loss of carbon sequestration has not yet received a price tag.

Mangroves have a considerable impact on climate as a Carbon sink, despite only being found in tropical areas, covering an estimated 140,000 square kilometers – less than 3 percent the extent of the Amazon rainforest.

One past study has estimated the monetary value of the benefits, or “ecosystem services,” provided by mangroves at $194,000 per hectare annually, meaning the world’s remaining mangroves provide around $2.7 trillion in services every year when multiplied by their global extent. A more recent study published in Environmental Research Letters, finds mangrove soil held around 6.4 billion metric tons of carbon in 2000. This is dramatically higher than previous estimates that pegged the carbon content of mangroves (both soil and biomass) at around 4.19 billion metric tons.

The question remains as to whether mangroves stand a chance to be restored?

Failed Mangrove restoration projects have been closely analyzed with numerous mistakes identified, to create a new framework for success that ensures:

  1. Scientists, ecologists, and botanists must all be on board to ensure the correct mangrove species selection is planted – one of the major downfalls of the world bank failed project was putting the wrong species in the right location.

  2. The selection of the location is vital, and according to the late ecologist and mangrove expert, Roy Lewis, “mangroves like a 30/70 wet to dry ratio. Recreating their original hydrology is essential.’

  3. Support from local authorities is essential. Without this, licensing to remove old infrastructure, monitor and evaluate newly planted mangrove species will most likely lead to failure of a project.

  4. It is not cheap – whereby nature always takes over as the largest restorative agent, in order to reestablish the original flow of water after a large development infrastructure has played around with natural water channels, a hefty price is often involved. Funds are needed to secure a long-term success.

  5. Local communities should be engaged in planting and most importantly, be trained in the ongoing monitoring and stewardship of new mangroves.

  6. Environmental mangrove disasters may hamper the project (extreme weather, infestations etc..)


In the case of Union Island, it would take more than a decade to restore the Ashton Lagoon to 90% of its original state, with multiple challenges along the way. The causeway cut off natural water circulation causing events such as eutrophication to rat infestations.

Time taught valuable lessons. Not only have fisheries returned, but they’re now thriving more than ever. Bees are pollinating flowers within the mangroves, bird sanctuaries have been created – driving a thriving tourism boom both local and international.

Best of all, precious carbon sequestration processes have been restored, operated by the plants themselves and within the soil structure below the roots.

To learn more about the role of carbon markets, take a look at our VOICE article on ‘4 things You Should Know About the Carbon Market

Read about the details of how locals and scientists achieve Ashton Lagoon mangrove restoration here: The Caribbean mangrove forest that defied destruction – BBC Future

[1] The Loss of Species: Mangrove Extinction Risk and Geographic Areas of Global Concern ( [2] Destruction of Carbon-Rich Mangroves Costs up to US$42 billion in Economic Damages Annually – UNEP Report [3] eHALOPH – Halophytes Database ( [4] [5] Destruction of Carbon-Rich Mangroves Costs up to US$42 billion in Economic Damages Annually – UNEP Report

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