We've Started Another Forest... but this time Underwater!

Built a nursery to produce green gravel at a capacity of 80 trays per cycle (80cm x 40cm each).

Agreement signed with project partners to fund green gravel production cycles for 2023.

Production of green gravel in the nursery.

Deployment of green gravel at two trial sites over an area of 0.03ha

The second production cycle deployments of the year completed at Cascais and the Berlengas islands- 160 trays with about 300 pebbles in each.

The green gravel we deployed did not survive the winter. Follow the link below for a full update, including our next steps. 

Deployments of 33,600 green gravel stones (which had been growing in the nursery since last year) on the south of Guia reef in Cascais. This batch was deployed along with kelp seeded on natural fibre lines attached to the seafloor to provide more stability against turbulent waters.

20,550 green gravel stones were deployed in two batches. One using the 'sea-socks' technique at a depth of 17m at a test site in Peniche. The other batch was deployed at a new depth of over 40m at a trial site south of Berlengas Island.

Results of our first kelp restoration trial

Our ultimate goal is to make large scale restoration of kelp forests a reality in Portugal and our first step in this direction was the kelp restoration trial we started with SeaForester in Cascais in November 2020. We deployed spores from healthy kelp populations into 3 sites. The results so far suggest that this spore bag technique will not work in this area, possibly because of the presence of turf algae that outcompete the kelp for rock surface. Although we were disappointed with the result, the information we got out of the project is valuable and is already helping guide our next steps. 

Green gravel is a kelp restoration technique that was recently developed by the Norwegian Institute for Marine Research (IMR). It involves seeding pebbles with kelp in a lab, allowing the kelp to grow under optimal conditions and only then deploying them in the ocean. The potential is huge because this technique can overcome many of the challenges facing current kelp restoration methods. 

Since pebbles can just be dropped from a boat, large areas could be restored without the need for more costly and time-consuming scuba diving work. What’s more, since the kelp is already attached to a substrate (the pebbles) it may grow well even if the underlying reef is degraded and covered in turf algae. The technique worked well in turf-covered reefs in Norway so we hope it will also be useful in addressing this problem in the areas in Cascais where releasing kelps spores is not proving to be enough to bring the kelp back. 

The method is now being trialled in more than 10 locations across the world in a collaborative effort coordinated through the Green Gravel Action Group. In Portugal, the SeaForester team, including researchers from the Marine and Environmental Sciences Centre - Politécnico de Leiria, have successfully used the technique in small scale trials. Individuals of the golden kelp, Laminaria Ochroleuca, have been successfully deployed on the ocean floor and have grown well over several months. This is very encouraging and means that we are ready for the next step!

Given the success of the initial trials in Peniche and the great potential of green gravel as a marine reforestation technique, we decided to scale things up. With the support of our Mossy Earth members as well as Not Just Travel, Get Set Hire, Unifrog and WSL Pure, we managed to get the funds needed to build a kelp nursery that will greatly increase the green gravel production capacity in Portugal.

This amounts to a total of 80 boxes which we are mounting in a shelf system which allows each of them to maintain about 200 to 400 pebbles under optimal conditions for the kelp to grow in the lab. Each box is illuminated by an LED light that switches on and off to simulate night and day cycles. Water flows through the boxes and is filtered and cooled so that it is kept suitable for kelp growth. 

The kelp nursery will be running year-round with a new batch of kelp pebbles being ready to deploy every 2 to 3 months. Each cycle begins by spraying the pebbles with microscopic immature life stages of the kelp which attach to the pebbles and start growing. To avoid the need to collect this starting material from wild populations every time we are also building a lab setup that allows us to keep a seedstock available year-round. This is a modified fridge contraption that allows the seedstock to be kept at the necessary light and temperature conditions. This makes it much faster and cost-efficient to start each production cycle because it is no longer necessary to find and collect material from wild kelp populations every time. 

Altogether this will allow the green gravel technique to be tested at a much larger scale in Portugal! 

The kelp seed stock has to be kept under special conditions in this "phytochamber" built for this project. The added flexibility to start a kelp production cycle without getting material from wild populations should be a game changer! 

Getting the water to flow in and out of every box requires a lot of tube fitting (and leak fixing!)

Each small task adds up. In this case, fitting an LED over each box takes a while if there are 80 boxes!

Cables, many cables. Getting them all in order was the main challenge of getting the light system up and running. 

Pictures from the construction and troubleshooting process

Learn more about the context behind this project

The world’s shallow coastal areas, where sunlight penetrates, are the cradles of the ocean. Here seaweed forests grow supporting a rich and diverse assemblage of marine fauna and flora by providing highly productive three-dimensional habitats. In addition to reducing the loss of biodiversity in oceans, kelp forests also provide ecosystem services by reversing acidification, an important part of climate change mitigation.

Unfortunately, European seaweed forests are disappearing at an alarming rate. Although we lack the data to figure out the actual causes for this decline, these are likely to be important drivers in many areas:

Climate change affecting water temperatures

A build-up of sediment as a result of both human and natural causes

Increases in herbivory rates due to overfishing and its impact on coastal ecological communities

Unlike land-based deforestation which has received a lot of attention, the loss of marine forests tends to go mostly unnoticed. This may be due to the fact that the underwater world is out of sight for most of us and its deterioration is therefore not as obvious. As result, there are still very few seaweed restoration projects in Europe and there is a great need to develop greater know-how in this area. This is where our partnership with SeaForester comes in to restore these 'forgotten forests'. SeaForester is an initiative that aims to reverse the alarming disappearance of seaweed forests in the world in order to safeguard the oceans’ vital role of carbon sequestration, maintaining fish stocks and securing the planet’s wellbeing. By joining forces with them in Portugal, we aim to make the large-scale restoration of kelp forests a reality here.  

Pioneering seaweed restoration work in Europe

Deploying trays of new green gravel out to sea and checking on previous deployments.

We've had an overwhelming amount of interest in this project which has raised some very interesting ideas from our followers! In this section, we will try to answer some of your most common questions and update it as we make developments. 

Would it be possible or practical to try for mixed species reintroductions?

Here are our current thoughts about mixing species, namely Laminaria Ochroleuca and Saccorhiza Polyschides.

Golden kelp forests are often single species and this is not a problem so the analogy of a monoculture plantation on land doesn't really apply and it's not something we need to be worried about.

We could try and use S.Polyschides and it may be that it does better at some of our sites or that in some places there would be some sort of synergistic effect.

We do not want to spread ourselves too thin for now. We are already trying to understand the effect of many variables in the production and deployment process and it seems better for us to focus on a single species for now.

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Kelp restoration management plan 2022-23 .docx.pdf

We have built a kelp nursery to test an innovative marine reforestation technique at scale in Portugal.

Scaling up kelp forest restoration

Building a kelp nursery to produce and deploy green gravel kelp at scale

Underwater forests are an immensely important ecosystem: they support biodiversity, improve water quality and sequester carbon. Despite their significance for marine life and the fight against climate change, the loss of kelp forests from coastlines worldwide has captured much less of the spotlight on deforestation. This is why since 2020, we have been working with SeaForester to restore kelp forests in Portugal where large areas of kelp have disappeared. We have built a kelp nursery to produce and deploy kelp that tests a new method called ‘green gravel’ with the potential for large-scale marine reforestation.

We've made a few adjustments to help our green gravel kelp survive in the open ocean! See the first batch of the year being deployed by our partners SeaForester in Portugal.

How we're changing our kelp deployments | VLOG

An update on the first deployments of green gravel in 2024.

Green Gravel Update

Start rewilding today