AquaForest, from dredged sediments to mangrove forests

Today is 26 July. That may not immediately ring a bell to you, but this is the 'International Day for the Conservation of the Mangrove Ecosystem'. And it is necessary. Because, did you know that since 1980, half of the world's mangrove forests have disappeared?

And this, with mangroves being among the most productive ecosystems and offering a long list of important benefits. With our partners, we are working on the AquaForest project in Ecuador where we will create a new mangrove forest using dredged material from the Access Channel of Guayaquil. Dive into this project with two of our colleagues.

Can you summarise the AquaForest project in two sentences?

Vicky: AquaForest is a Nature-based-Solutions Living Lab. In this project, we will restore mangrove forests by making circular and sustainable use of dredged sediments.

When was the seed planted for this project?

Jelle: In 2018, we signed a 25-year concession contract to carry out maintenance dredging in the access channel to the port of Guayaquil in Ecuador. During the start-up of the project, we were looking for a good location to dispose the dredged material.

Vicky: The dredging area is part of the Guayas river delta which is covered with mangrove forests. Unfortunately, we also saw that a lot of mangrove habitats have been lost in recent decades due to aquaculture, agriculture, and urban and rural development. This has given free rein to coastal floods, coastal erosion, loss of biodiversity and has put a lot of pressure on water quality. Which in turn threatens local socio-economic development.

Jelle: And one plus one is two. So we decided to use our dredged material to raise lower areas in the delta and plant new mangrove forests there. A wild but also innovative idea that clearly took shape during an 'Innovation Challenge' (A corporate programme by Jan De Nul) in 2020.

That sounds very innovative. Is this the first time such a study has taken place?

Vicky: AquaForest is 'a first of its kind'. A project where dredging sediments are reused to create mangrove forests does not exist as far as we know.

Jelle: There is already a lot of literature on mangrove forest restoration, but it has not yet been applied in combination with circular use of dredge sediments. And we are now changing that. We are currently investigating several factors that are important for the optimal growth of mangrove habitats. In doing so, we are analysing the elevation, drainage, and sediment type of the area where the new mangrove forest will be located. But we are also looking at which plant species thrive best and whether we need to protect the juvenile mangrove trees from local hydraulic conditions in the beginning.

AquaForest is 'a first of its kind'. A project where dredging sediments are reused to create mangrove forests does not exist as far as we know.

Vicky Stratigaki

Senior Project Engineer Development & Conceptual Design

Where exactly will the mangrove forest be located?

Jelle: We will develop the new mangrove forest on an existing tidal flat area located in the Guayas river delta, 15 kilometres northeast of Posorja. This is in an area where models have shown that sediments are starting to deposit naturally.

What does the future direction of the project look like?

Vicky: As Jelle pointed out, we are currently researching various factors that affect mangrove habitats. Later this year, we will effectively construct a U-shaped island in the delta using dredged sediments. By creating the initial conditions that are necessary for mangroves to grow, afforestation will take place, both naturally and in an assisted manner. Our goal is, firstly, to support natural propagation of mangroves by creating the ideal conditions. Secondly, with the local community, we will also plant mangrove trees ourselves. This way, the mangrove ecosystem will eventually evolve into an autonomous habitat, where human intervention will no longer be needed. We expect to have the first mangrove trees by the summer of 2024.

This is a Nature-based-Solutions project, or literally translated: a solution based on nature. What exactly does that mean?

Vicky: The area in Ecuador encounters challenges like coastal floods and erosion, creating safety problems along the coast. To counter this, one could choose to build a dyke out of 'hard' materials. But we don't do that here. Instead, we opt for 'soft' measures and for a solution that we also find in nature: mangrove forests. They are a natural coastal protector and thus a Nature-based-Solution.

What will be the impact of this new mangrove forest?

Jelle: Besides natural coastal protection, mangrove forests have numerous ecological benefits. For instance, mangrove forests are important carbon sinks and can retain up to four times more carbon per hectare than tropical rainforests. In addition, they also serve as water filters. Mangrove forests also support socio-economic activities such as ecotourism and fishing. Moreover, they are a hotspot for biodiversity as well, attracting a lot of birds and marine life. In AquaForest, we will explore all these ecosystem services and determine the positive impact of mangroves.

Vicky: Keep in mind: this is a demonstration project. We will mainly use AquaForest as a Living Lab to conduct research with our partners, to gain new knowledge and gather information. We will test how efficient the mangrove habitat is against coastal floods and erosion, we will monitor the increase in biodiversity, but we will also examine the socio-economic benefits. This pilot project in Ecuador will pave the way for other similar projects in the region, as well as globally, in other locations where mangrove forests play an important role in local ecosystems.

This seems like an ideal project to realise collaboration and co-creation between different partners?

Vicky: That's right. We are coordinating this project, but we are working with an international project consortium: South Pole, Mantis Consulting, Haedes, University ESPOL in Ecuador, University of Antwerp, Vrije Universiteit Brussel, and the NGO Fundación Calisur. And each AquaForest partner has specific expertise. We also involve local authorities, government, researchers, and local communities.

The project is subsidised by Departement Omgeving (Flemish Government) and the International Union for Conservation of Nature (IUCN). AquaForest is further supported by the G-STIC Climate Action Programme 2022.

Together we are working on a project that contributes to many of the United Nations Sustainable Development Goals.

So we decided to use our dredged material to raise lower areas in the delta and plant new mangrove forests there. A wild but also innovative idea.

Jelle Evenepoel

Lead Engineer Marine Environmental Department