October saw a month spent in the town of Golfito on the South Pacific Coast of Costa Rica, working with the marine conservation charity Misión Tiburón. Their work focuses on shark conservation, recognising that sharks are indicator species. This means that high shark abundance indicates the good health of a wider marine ecosystems and the species found within it. Beyond their work on shark conservation, Misión Tiburón is actively involved in outreach and education, and combating other challenges such as marine pollution and overfishing. They were the winners of the 2022 St Andrews Prize for the Environment, a major international environmental award, through which I learnt about their work. Using this accolade, Misión Tiburón expanded another key area of their work: a mangrove forest restoration project in the Golfo Dulce region of Costa Rica.
In October, I visited Misión Tiburón to learn how ecosystem restoration and carbon assessments are conducted in mangrove ecosystems. With past experience on similar topics in saltmarsh and seagrass environments, I wanted to see how such fieldwork challenges are approached in another major coastal ecosystem.
During my time in Golfito, I learned about the various aspects of Misión Tiburón's work on mangrove forests, acquiring fieldwork skills in an ecosystem essential for climate change adaptation and mitigation. Seeing the first-hand impact of the St Andrews Price for the Environment, and continuing to build connections on Blue Carbon research between Misión Tiburón and the University of St Andrews, was a fantastic experience.
So, what aspects of Misión Tiburón's work did I get involved with over this month?
Mangrove Restoration:
The Golden Fern, Negraforra (Acrostichum aureum) is a fern species naturally found growing in the mangrove forests of Costa Rica. Around the town of Golfito, sections of the widespread mangrove forest have been illegally cut to sell the wood, leading the Golden Fern to grow out of control and cover the sections of deforested land in the forest. This prevents the trees from regrowing, as the thick canopy of fern blocks light and prevents mangrove seedlings from developing.
Misión Tiburón's mangrove restoration project, led by forestry engineer Javier Rodriguez, aims to remove the Golden Fern from areas in which it grows uncontrollably, planting mangrove seedlings in its wake. This allows the mangrove forest to regrow on the deforested sections and limits the amount of Golden Fern to its natural state.
Misión Tiburón has employed 30 workers, all locals from Golfito, to complete a project addressing the overgrowth of the Golden Fern. The team clears the fern that has overgrown sections of the previously deforested mangrove forest, then planting mangrove seedlings on the newly available land. During my stay, a two-hectare plot in the forest was being cleared of the Golden Fern, with 15 hectares having already been completed elsewhere. This project aims to reforest a total of 20 hectares by the end of November 2023.
Despite being a primarily marine-conservation focused charity, Misión Tiburón conducts work to maintain the integrity of Costa Rica's mangrove forests, recognising the importance of this habitat as a land-sea barrier. Javier equates mangrove forests to shields, protecting coasts from storm events, coastal erosion and sea level rise. Furthermore, healthy mangrove forests also filter water entering the sea, thereby improving environmental quality for nearby coral reefs and shark species. This is especially important in the Golfo Dulce region as Misión Tiburón have found the area to act as an important breeding and nursery ground for the critically endangered hammerhead shark species.
Several methods were considered for removing the fern, with Misión Tiburón ultimately electing to cut the fern into small systematic patches evenly spread throughout the reforestation plots. The fern is not completely removed, as the small patches of fern bind the soil limiting erosion, important for the survival of planted mangrove seedlings until their root systems develop enough to bind together the soil. Additionally, leaving some segments of the Golden Fern intact provides a refuge for animals such as crabs and serpents who would otherwise be left without a habitat by the clearance of the plant. Javier additionally adds that the Golden Fern is not an invasive species, it is found naturally occurring in this environment and so completely eradicating it would also be harmful to the ecosystem. The aim is not to eradicate the fern, but return it to a natural level in the ecosystem by allowing mangrove trees to re-grow.
When cutting the fern, it is essential that not only the plant is cut but the actual root is chopped to pieces to prevent it from quickly re-growing. After the fern is cleared, mangrove seedlings are planted in the newly cleared area. Two species are planted: Mangle caballero (Rhizophora racemosa) and Rhizophora mangle (Mangle gateador), due to their high occurrence in the surrounding intact sections of the forest, suggesting that they are well-adapted to local conditions.
Misión Tiburón has formed a community association for the workers involved on this project, the 'Asociación de Conservación y Ecotourismo de Golfito'. This helps to secure additional funding and work benefits for their employees, such as computers and telephones. Of the 30 workers on the project, many are women, elderly and young people, and those with a background in fishing and construction. These groups represent key demographics that often struggle with employment in the Golfito region. This project has deliberately tried to involve locals from all sections of the community to make it an inclusive work space and to show that conservation can generate additional benefits for everybody in the neighbouring community. Maria Galo, the eldest woman employed on the project, explains that she enjoys working on the project because she knows that she is doing will benefit the future generations of Golifto, even if she will not get to directly see these benefits herself.
The mangrove restoration project is incredibly hard work, involving hours in the hot sun on muddy, unstable ground clearing the incredibly thick Golden Fern. After seeing this project first-hand, I have immense respect for all the people working to clear the fern and plant the mangroves. It was incredible to see how passionate they are about this project and their strong belied in the positive environmental impact that it is making.
Mangrove Forest Monitoring:
In addition to working on restoring deforested sections of the mangrove forest, Misión Tiburón conducts environmental condition monitoring across sections of the intact mangrove forest in the Golfo Dulce region. The aim of this work is to understand the health and condition of the forest, and to gain a baseline understanding of areas where deforestation and pollution are significant concerns.
For monitoring, a section of the forest is selected and a 10m-by-10m plot established 25m from the river border. Moving away from the river and into the forest, two more plots are established, each 50 metres apart, so that a total of three plots are assessed in one day. Three plots are used for monitoring to account for differences in the forest structure based on distance from the river. More than three plots are not established as moving deeper into the forest would becomes impossible due to the difficulty of walking through an intact mangrove, and the limitation of low tide times and daylight hours.
In each monitoring plot, all mangrove trees are marked and their diameter, height, and species recorded. In addition, the presence of other species in the plot - for example the Golden Fern - is also noted. Lastly, in the one metre area around each of the four corners of the monitoring plot, all crab holes are counted as an indicator of invertebrate numbers. This data is added to a spreadsheet, and spatial mapping software such as GIS is then used to evaluate the state of the wider mangrove forest based on the calculations made across various monitoring plots. Other factors are also recorded, such as sightings of deforestation and marine mammals. However, at this point in time these factors are observational recordings and not quantitative measurements.
Another monitoring method employed by Misión Tiburón is a trash, mammal and Golden Fern rapid assessment. This involves a line of people, spaced approximately 10 metres apart, walking from the start of the monitoring plot closest to the river 50 metres into the mangrove forest and noting down the number and type of all plastic items, mammals, and Golden Fern plants seen. This provides an indication of the level of plastic pollution in the forest, which species use the habitat, and whether Golden Fern levels are natural.
Identifying spots in the forest with high levels of plastic pollution helps Misión Tiburón select locations for volunteer clean-up activities, as well as provides evidence for government lobbying in favour of stronger regulations on the use of plastics and stricter recycling laws.
Seeing which species use the mangrove forest is also key, showing the importance of habitat preservation and generating additional funds for mangrove restoration. During my time, I saw many Capuchin monkeys across the plots.
Blue Carbon Assessments:
In association with winning the St Andrews Prize for the Environment, over the past year Misión Tiburón has begun incorporating Blue Carbon into their work on mangrove restoration. Mangrove forests are known to sequester five-to-six times more carbon than terrestrial forests, making them incredibly important sites for mitigating the impacts of greenhouse gas emissions. Due to this incredible ability, there is growing international support for raising finances to protect blue carbon ecosystems. Misión Tiburón recognises the importance of understanding the role of Costa Rica's mangrove forests in carbon sequestration, and the additional support and financing for the protection of the Golfo Dulce region that this could generate.
In order to assess the amount of carbon sequestered in the soil of the mangrove forest, 1-metre long soil cores are collected from the centre of each of the established mangrove monitoring plots. Each 1-metre core is cut into 20cm fragments, as more carbon is known to accumulate in soil over time, thereby making the soil carbon content at depth much greater than what is found on the surface. All samples collected in the field are currently undergoing laboratory analysis to obtain data on their carbon storage content. When the carbon content for all 20cm fragments in a 1-metre core is assessed, the total carbon storage in the top metre of soil sampled from each plot will be known.
Using a methodology outlined in the Blue Carbon Manual, produced by the Blue Carbon Initiative, the data on the carbon stored in each core can then be used to extrapolate the total carbon stored in the 10m by 10m monitoring plot from which it was taken, and with similar data collected across many plots and the area of the overall forest assessed using aerial footage, the entire carbon storage potential of a forest can be estimated.
It was very interesting to compare the soil core collection procedure in a mangrove ecosystem to those I am familiar with in saltmarsh and seagrass ecosystems in Scotland. The main difference is the difficulty of traversing a mangrove forest with the equipment to take the soil sample. It's hard work to carry a metre-long corer and a cooler in which to store soil samples whilst pushing your way through mangrove roots and avoiding getting stuck in deep mud. At the start of one of the sampling days I got stuck in mud up to my knees and had to dig my wellies out using my hand!
Ocean Literacy Programme:
In addition to their fieldwork on marine and coastal conservation, Misión Tiburón conducts an Ocean Literacy Programme in schools across Costa Rica. This programme is part of the United Nations Ocean Culture Education Programme, and involves conducting a series of eight workshops at a school introducing children to various topics relating to the marine environment. One such topic is marine plastic pollution, introducing school kids to the problem and to potential solutions that they can incorporate into their daily lives. Through conducting such workshops, Misión Tiburón instills a care for the environment into children across Costa Rica whilst providing them with actions through which they can actively participate in marine conservation.
I participated in workshops across two schools in the Golfito region, covering topics about mangrove restoration, climate change, and plastic pollution. It was incredible to see how interested pupils of all ages were in these topics, clearly wanting to make a difference and to help protect marine and coastal environments.
Hammerhead Shark Tagging:
The final component of Misión Tiburón's work in the Golfo Dulce region that I joined is the tagging of young hammerhead sharks. This region has been identified as a breeding and nursery ground for this critically-endangered species, leading the Golfo Dulce region's designation as the first hammerhead shark sanctuary in Costa Rica.
Every month, Misión Tiburón conducts a systematic survey of hammerhead sharks in the area to gather data on their reproduction and growth. The sharks are caught using a baited hook and pulled on board, where their length is measured and gender recorded. After this is done, a plastic tag is put through their dorsal fin with a number and Misión Tiburón logo. If a tagged shark is caught at a later stage of its life - for example, as bycatch in fishing - or if it is seen by divers, this can be reported to Misión Tiburón to reveal information about the growth and movement of the species.
Overall Reflections
Although I came to Golfito with the plan of only working on the mangrove forest stock assessments, I was lucky to participate in all aspects of Misión Tiburón's work in Golfito. From this I gained a well-rounded understanding of the importance of the various branches of their work, and saw how their projects all fit together to create marine conservation with a wider impact. I
I was amazed by all the Misión Tiburón employees that I met. The passion and love that they have towards their work, and their determination to ensure that environmental conservation is conducted in a community-oriented manner is truly inspiring.
I have acquired a good understanding of how to conduct fieldwork in a mangrove ecosystem, specifically understanding the added challenges of soil sampling in very muddy and thick forests that can only be reached by boat at low tide. The difference in answering the same research question in this ecosystem vs. a saltmarsh or a seagrass meadow is something I would have never understood without getting to experience it firsthand, so I am incredibly grateful to how gotten this learning opportunity. Additionally, learning about how mangrove restoration connects to shark conservation, something I had never considered before, and getting to see a hammerhead shark for the first time in my life are experiences that I will cherish forever.
I look forward to keeping in touch with Misión Tiburón and using what I learnt from them to develop further stages of my R&A project, as from the lessons I got from them I am confident in my ability to contribute to projects in mangrove environments.
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