Next to coastal development projects, one of the primary causes of mangrove forests’ decline worldwide is illegal logging for timber and charcoal production. This has contributed to the disappearance of thousands of square kilometres of mangroves. This process needs to be urgently reversed.
However, we also need to square the circle. We need to conserve all mangrove forests while enabling people to use the wood from mangroves legally for construction, charcoal production and other purposes.
So how do we square the circle? One idea being tested is the feasibility of having forests which float on the ocean. On 6 November, UNESCO Programme Specialist Susan Schneegans presented this idea to the Small Island Developing States Solutions Forum organised in Fiji by FAO.
What if mangroves could float? If so, their narrow range in the intertidal space between land and sea could be widened to include vast stretches of the surface of the ocean. Coastal mangrove forests would be complemented by floating mangrove forests.
Sound farfetched? Actually, the idea has already been tested and it seems to work – even if there remain many unknowns.
A UNESCO concept
The concept of floating mangroves is the brainchild of UNESCO ecologist Benno Boer, who tested it in Qatar from 2012 onwards.
‘While I was based at UNESCO’s office in Doha, I planted mangrove seedlings in 20 boxes at the marina to see if they would germinate and survive,’ explains Dr Boer. ‘The concept I tested allows seawater to flow into and out of the pontoon to irrigate the mangroves’ roots. The seeds germinated very rapidly. Years later, I was able to see with my own eyes that the mangroves had thrived in their floating box, without the need for freshwater or land’.
Time to field-test floating mangroves in Fiji
Since 2018, the University of New South Wales has been partnering with UNESCO to take Project Halophyte, or Project Halo for short, to the next level. The word ‘halophyte’ derives from the Ancient Greek words for salt (halas) and plant (phyton), in a nod to the salt tolerance of mangroves.
Currently, a research team working under Professors Andrew Dansie and Will Glamore is developing scale models of pontoons at which it has been throwing storm surges in the lab to test their stability and explore different design options for floating mangrove structures.
Professors Dansie and Glamore now plan to test fully sized pontoons in Fiji, which will be scaled to need. These pontoons will be set up in sheltered lagoons and estuaries.
The project is being implemented in partnership with the University of the South Pacific and the Government of Fiji and with philanthropic funding from Swire Shipping. A Steering Committee has been established, of which UNESCO staff are members.
Engagement with local communities and other stakeholders will be central to Project Halo. ‘Starting in early 2025, we researchers shall be engaging with local knowledge-holders and landholders in the design and implementation of the project’, explains Andrew Dansie. ‘Local knowledge-holders and landholders will be members of the Technical Advisory Group. They will also be involved in collaborative research’.
The first step will be to re-introduce the natural tidal cycle in coastal areas of Fiji where mangroves have been cut down. Natural processes will then regenerate the mangrove forests which once grew here. These mangrove forests had been cut down last century and replaced by seawalls to keep saline and brackish waters out and enable the area to be planted with agricultural crops like sugarcane.
‘With sea-level rise, king tides and saltwater intrusion into soils, farmers are now looking for alternative sources of income’, observes Andrew Dansie. ‘The project in Fiji for wetland restoration should provide them with options’.
© Andrew Dansie.
Numerous advantages for local communities
There will be a lot of advantages for local communities. The floating plantations will remove pressure from the restored mangrove forests on the shore, as the wood from the floating mangroves could be harvested.
Mangrove leaves from the floating forests could also be harvested and fermented to produce fish feed.
In addition, the design and location of the “pontoons” should attenuate the strength of the waves and offer a measure of coastal protection.
These ocean forests will not take up space needed for forestry and agriculture. Nor will floating mangroves need to be irrigated with freshwater, unlike land-based agriculture.
The mangrove forests will be able to take up agricultural run-off that ends up in rivers and the sea by absorbing nitrogen, phosphate and potassium, thereby reducing marine pollution.
They will also support local fisheries. Fishers have observed that, when local mangrove forests are cut down, their catches of seafood decline. This is because mangroves are at the start of the food web. Marine bacteria and fungi depend on them, as do seashells and fish.
The mangrove forests will also be extremely effective at sequestering carbon.
In other words, mangrove forests can be considered one of nature’s superheros.
‘We encourage the private sector to join the project’, says Benno Boer, ‘and to develop the concept further, including by coming up with original designs for the pontoons’.
There is a lot of potential for floating mangroves in Fiji, as the entire archipelago is rich in mangroves. They cover 2.4% of its territory, or 425 km2.
© Andrew Dansie.
Still many unknowns
There remain a lot of unknowns. Which are the best materials to use for the pontoons, for example? Wood, Fibreglass? Another material?
What is the best way to anchor the pontoon to the seafloor?
Will private companies find floating mangroves an economically viable endeavour?
Could floating mangroves on pontoons survive in the more turbulent waters outside sheltered lagoons and estuaries?
How can we transport the pontoons using clean sources of energy?
Project Halo intends to answer as many of these questions as possible – and more.
© Rich Carey/Shutterstock
