The value of mangroves

Assoc Prof Friess with two visitors at the Sungei Buloh Wetlands Nature Reserve, one of Singapore's mangrove forests

As Singapore’s landscape developed over the years, the number of mangrove forests in the country has declined significantly to make space for reservoirs and urban infrastructure. Almost 90 per cent of our mangroves have been lost, mostly over the last 70 years, shared NUS Geography Associate Professor Daniel Friess. What are the impacts of this loss?

Or in the words of many, so what? What do these mangroves do? Why should we care about them? Are they just nice places to visit or do they do anything more?

Compelled by these questions, Assoc Prof Friess, an ardent mangrove lover, together with a team of 10 graduate and undergraduate students, spent the past three years studying mangroves in Singapore with the aim of “trying to work out the value of mangroves, what they mean to us and what they give us”.

In that time, the team identified and quantified a large range of benefits that mangroves offer to Singapore.

One of the unique areas that the team looked into was quantifying the cultural benefits of mangroves, making use of photographs posted on websites such as Flickr.

“If someone takes a photograph of the landscape, we assume that is because they appreciate, or take value from the landscape; people think the view is nice. That is a type of cultural value. If they take a photograph of a crab or otter, they’re valuing the biodiversity there. Taking selfies means that people value social recreation, using the places as social spaces,” Assoc Prof Friess explained.

These geo-tagged photographs allowed the researchers to create maps that would approximate the value of different parts of the mangrove to people. This could be used as a tool to help managers improve visitor experience in nature parks.

In Singapore and other urban areas there are a lot of different demands on land, but we can use information on the benefits of mangroves to prioritise and optimise our planning so we get what we hope is a win-win situation.

Other areas where mangroves provide benefits include acting as nursery habitats for commercially important fish species, defending the coast against tides and storms, and storing carbon.

“Mangroves that we sampled had very different fish communities from other habitats,” shared Assoc Prof Friess. This means that without mangroves, there could be a possibility of losing those species of fish.

The tangled roots of many mangrove species can also help to defend the coast, he said.

“When the waves hit the roots, they take out the energy of the wave so that by the time the wave travels through the mangrove, it’s a lot smaller. This means that we don’t have as many problems with erosion, and it is easier to maintain our seawalls,” Assoc Prof Friess elaborated.

Mangroves take carbon out of the atmosphere during photosynthesis and can store it in the tree and soil. Their carbon storage capability outranks many other forests, and can be up to five times more efficient at doing this than a tropical rainforest. Assoc Prof Friess added that their presence in Singapore can be used to offset our carbon emissions.

“In total, Singapore’s mangroves store some 450,000 tonnes of carbon, which is equivalent to the annual carbon emissions of 620,000 people or up to 3.7 per cent of annual emissions in Singapore,” he shared.

However, the carbon storing ability of mangroves also has its downside.

“If you lose mangroves, you lose more carbon per hectare. They have a bigger impact when they’re lost, compared to other types of ecosystems. So on one hand it’s great that mangroves store so much carbon, but on the other hand it’s very bad because they can release more carbon too. So we have to really protect them,” Assoc Prof Friess emphasised.


Assoc Prof Friess (left) with his two NUS Geography final-year students Seah Li Yi (middle) and Aleena Kua (right) studying a mangrove forest

Looking towards the future, he hopes that the team’s findings can be used to help guide future planning.

“In Singapore and other urban areas there are a lot of different demands on land, but we can use information on the benefits of mangroves to prioritise and optimise our planning so we get what we hope is a win-win situation ,” he said.

Assoc Prof Friess and a large team of collaborators have secured funding to use a similar approach to study all ecosystems in Singapore to determine the benefits they can offer to the country.

See press release