Pierre Failler and Ewan Trégarot: “Protecting an Ecosystem Doesn’t Cost Much, but Pays Immense Dividends!”

How did you evaluate the monetary value of a park such as the Banc d’Arguin?

We first studied the direct use value of activities such as fishing and tourism; indirect use value such as carbon sequestration, the role of fish nurseries, and bioremediation; and non-use value such as its existence and its legacy for future generations. The concept of total economic value (TEV) provided the conceptual framework to take all these values into account. 

These types of studies have been carried out since the 1980s, but there was no complete study on the PNBA, which is one of the largest and oldest protected areas in West Africa. We were therefore able to assess the health of the ecosystem and quantify the services rendered. In total, the annual monetary value of its main services—regulation and provision of resources—is estimated at €200 million/year. When we plot this to the park’s surface area, this amounts to €40,000/km2/year. 

In comparison, the value of the primary services rendered in the five Marine Protected Areas in West Africa (Langue de Barbarie in Senegal, Rio Cacheu and Urok in Guinea-Bissau, Tristao and Alcatras in Guinea, and Santa Luzia in Cape Verde) amounts to €26,000/km2/year, for a total value of €35 million/year for all five MPAs. The value of the PNBA is therefore higher.

What is the park’s most valuable “service”?

In the case of the PNBA, carbon sequestration by seagrass is the most important service: around 40% of the total value. The park has vast seagrass meadows, almost 700 km2, which were probably underestimated during analysis of satellite images, given the turbidity of the water.

On a global scale, seagrass stores 10 to 15% of organic carbon in the ocean, playing a major role as a carbon sink. The carbon is stored both in the living biomass (leaves, rhizome, roots) and in the sediment. The carbon stored in the sediment is the result of a very long sequestration process. Seagrass beds therefore have considerable storage capacity. 

In Mauritania, 11% of the country’s total greenhouse gas (GHG) emissions are sequestered by the PNBA’s marine ecosystems. According to predictions, the north shore of the Senegal River, another major source of sequestration, could become a desert by 2100. The park’s seagrass would then become the country’s only major carbon sink.

Fishing federations want to open up the park to small-scale fleets in the northern part of the country. They see the park as just a simple reservoir for fish. It is indeed a reservoir—as part of the study, our colleagues from the Mauritian Oceanographic Institute (IMROP) estimated that 20% of the biomass fished in Mauritania’s EEZ comes from the PNBA—but it’s also much more than that. Its role as a carbon sink is significant.

Learn more about AFD’s work to support biodiversity protection

What lessons have you learned from this work?

This study gave us a general sense of the state of this ecosystem and its value. It is of course futile to reduce a natural space to just its monetary value, but this information can also be useful in dialogues with all stakeholders. It shows that managing such a park is not that expensive, €1 to 2 million per year, while it brings in almost 200 million if we take into account all the services rendered. This is without counting other services that the study did not calculate, such as those rendered by birds, which deserve closer attention.

The PNBA, and more generally protected ecosystems, have value. Their protection creates value and increases ecosystem resilience to anthropogenic and climatic disruption. Healthy ecosystems provide more services and are more resistant. In the end, protection doesn’t cost much, but pays immense dividends! 

In light of the study, what challenges remain for the PNBA and Mauritian authorities?

Pollution, particularly from plastic, is a real problem. It mainly comes from fishing gear debris from dugout canoe traffic outside the park. It is also significant around villages that don’t have any way to process it. People typically aren’t aware of the extent of this pollution and its medium- and long-term consequences

Overall, it seems that Mauritian authorities are not yet aware of the opportunity this park offers for climate change mitigation. Their approach is still largely focused on preserving biodiversity. Yet the park will contribute 20% of the country’s commitment to reducing its GHG emissions as part of the Paris

Climate Agreement. This is significant. It makes an immediate contribution at a very low cost. This exceptional benefit makes this park even more precious.

AFD supports the activities of the Banc d’Arguin National Park via BaCoMab, a Mauritian conservation trust fund.

The study evaluating the Banc d’Arguin’s ecosystem services (in French) was published in December 2018.