The study has been conducted in the Fatick region, in the Sangomar Marine Protected Area (AMPS), located between latitudes 13˚35' and 14˚10' north and longitudes 16˚50' and 17˚00' west, and covering the communes of Palmarin and Dionewar. The AMPS is bounded to North by the Joal Fadiouth MPA, to the South by the Saloum Delta National Park and to the East by the Palmarin Community Nature Reserve (RNC) and the Communes of Bassoul and Djirnda [15] ( Figure 1 ). The main activities are fishing and malacological gathering, processing of fish products, agriculture and livestock farming [16] . Temperatures range from 17˚C in January to 37˚C in June, with an average of 27˚C. A short rainy season lasting around four months, with low intensity in July and August, with average rainfall of 155.1 to 265.7 mm following the arrival of the monsoon, the hot, humid wind that blows from mid-June to mid October and brings rain (Foundiougne weather service, 2016). The commune is characterised by the presence of leached and slightly leached tropical ferruginous soils, low-lying areas or basins and halomorphic soils. Surface water in the area is mainly made up of the Atlantic Ocean, which runs alongside the western part of the local authority. The Saloum River is also a major source of water, feeding several bolongs and ponds in the region. Vegetation in the AMPS varies from mangrove forests to dryland forests, shrub savannahs and herbaceous ground cover. The AMPS is also rich in wildlife. These include migratory birds (pink flamingos, pelicans, terns, green bee-eaters, grey herons, etc.), mammals such as hyenas, jackals, raptors, genets, patas monkeys, etc, reptiles (marine turtle, crocodile, Nile monitor, python, snake, etc.) and aquatic fauna (fish, arches, shrimp, murex cymbium, etc.) [16] .

The study was conducted in the villages of Niodior, Falia and Dionewar in the Dionewar municipality, which is centred on the AMPS. The choice of this commune was justified by the activities carried out by its population in the AMPS. Purposive sampling was adopted for this research. Taking into account the ecosystem services provided by the AMPS, all socio-professional categories were surveyed. These included women who process fish products, gatherers of non-timber forest products (NTFPs) grouped together in the Resource Management Committee (COGERE), pirogue operators, hoteliers, carters, fishmongers, farmers, stockbreeders, honey producers, tourist guides, salt producers and households affected by high winds. Given the difficulty of assessing ecosystem services, and in order to ensure the reliability of the information, focus group interviews were conducted in each village and for each category of service targeting the specific socio-professional group. For each socio-professional category, the focus group involved 10 members chosen, with the help of the manager, on the basis of their experience in the field (over 3 years), their strong involvement and their knowledge of the field. In addition, semi-structured individual surveys were carried out among AMPS agents and those of the fishing service in the said villages. To assess the importance of the various types of service, each focus group participant was assigned a score (ranging from 1 to 10) to each type of service.

The study assessed the total economic value of 4 categories of ecosystem services: provisioning, cultural, regulatory and support services. The general information gathered was the identification of the types of stakeholders and the frequency of use of the services. To assess the total economic value, a specific questionnaire was drawn up for each category of service. For supply services, the questionnaire provided information on the different types of products harvested and processed, the frequency and quantity harvested and the unit market price. For the regulation services, the information requested included the number of houses located within 300 m of the coast in order to quantify the cost of avoided damage to these houses, as well as the number of houses or infrastructures damaged by violent winds and the expenditure incurred in repairing them (replacement cost method). As for the support service, the questionnaire provided information on the AMPS budget and investment by its various partners. With the cultural service, the tourist campaign, the price and duration of stays and the price to be paid for walks were the main information collected.

The importance of the different types of services (scores) was submitted to Anova using R 4.3.1 software. The Excel spreadsheet was used for the calculations and figures.

To assess the annual economic value of the supply service, NTFPs harvested and processed, fishery products and agriculture were considered. Formula 1 was used:

$\text{Annual economic value ofsupply services}=\sum \text{annualquantity harvested}\left(i\right)\ast \text{market cost}\left(i\right)$ (1)

where i is the service provided.

Livestock services were estimated using the replacement cost method. The quantity of fodder was estimated on the basis of the work of NDIAYE [17] , according to whom the minimum consumption of concentrated feed is estimated at one to two bags of concentrates per month, depending on the size of the herd. It should be noted that in these villages, the animals are left to graze freely.

In the case of cultural services, tourism, including walking, and shipping were taken into account. They were evaluated by equations 2 and 3 respectively:

$\begin{array}{l}\text{Annual economic value of tourism}=\text{number of days in the tourism campaign}\\ \ast \text{average daily number of tourists}\ast \text{average daily rate}\end{array}$ (2)

$\begin{array}{l}Annualeconomicvalueofshippingservices=Numberofaveragedailypassengers\\ \ast numberofdailyjourneys\ast 365\ast priceperperson\end{array}$ (3)

Given the remote and rural nature of the study area, local people are not aware of the cultural services associated with education and contemplation. As a result, it was not possible for the local people, the main beneficiaries, to assess the economic value of these services.

With regard to regulating services, carbon sequestration, erosion regulation and strong winds were taken into account. For carbon sequestration, a land use map of the AMPS was designed using QGis software. According to PROGED-2; KAUFFMAN and BHOMIA [18] [19] mangroves sequester 55 t x ha⁻¹x yr⁻¹, open forests 52.60 t x ha⁻¹x yr⁻¹ and wooded savannahs 30 t x ha⁻¹x yr⁻¹ and shrublands 45.21 t x ha⁻¹x yr⁻¹. The average price of ton of carbon sold on the voluntary market is between 1850 and 5250 FCFA, i.e. an average of 3550 FCFA.t⁻¹ [4] . Thus, the annual value of sequestration was given by formula (4).

$\begin{array}{l}\text{Annual Economic value of carbon sequestration}=\sum \text{Annual sequestrated quantity per ecological unit}(i)\\ \ast \text{Voluntary carbon market}\text{cost}(i)\end{array}$ (4)

where i is the service provided.

With regard to the regulation of erosion and flooding, the assessment was made using the method of the replacement cost of infrastructure, particularly houses located less than 300 m from the coast. According to NOUMEYI [4] , mangroves reduce by three quarters the destructive effect of erosion and strong winds for houses located less than 300 m from the coast. According to AJONINA et al. [20] , the gains in restoration costs allocated to mangrove ecosystems for protection against flooding and moderation of the effects of high winds amount to 40%. On the other hand, for the regulation of the effects of violent winds, the economic evaluation of the expenditure incurred for the repair of damaged houses or infrastructures was carried out. Formulas 5 and 6 were therefore applied.

$\begin{array}{l}\text{Annual economic value of Flood and erosion protection}=\\ \sum \text{Total cost of infrastructures located from 300 m less than the mangroves}(i)\\ \ast 40\%\text{of protection due to mangroves}(i)\end{array}$ (5)

where i is the service in question.

$\begin{array}{l}\text{Annual economic value of moderate violent winds}=\sum \text{expenses on wind-damaged homes}(i)\\ \ast 40\%\text{of protection due to mangroves}(i)\end{array}$ (6)

where i is the service provided.

To assess the economic value of each category of service, the sum of the different types of service making up the category was calculated.

The support service was evaluated using the method of NDIAYE [17] , according to which the value of this service is equal to the sum of the WHPA budget and the amount of investments made by partners for biodiversity conservation.

The total economic value was assessed by adding together the values of the 4 service categories.

Fishermen are in the majority (48%), followed by women who process fish and forestry products (29%). On the other hand, tourist guides, hoteliers, livestock farmers and fishmongers account for the smallest proportions (1, 1, 2 and 2% respectively) ( Figure 2 ).

Indirect actors in the AMPS—carters—are in the majority (42%), followed by box hire companies and resellers with the same proportion (16%). However, conservation and development NGOs are in the minority (4%) ( Figure 3 ).

The Sangomar Marine Protected Area (SMPA) provides a total of four ecosystem services to the inhabitants of the Dionewar municipality. These include: provisioning services, which are the goods that people obtain directly from the MPA, such as collecting firewood, fishing, gathering NTFPs, food and medicines. Regulating services, which serve to regulate the ecosystem and combat flooding, coastal erosion and violent winds. Support services, which serve to support the other services. Cultural services, which are the intangible products that communities derive from the MPA, such as tourism, walking, education and research ( Table 1 ).

People’s perception of the importance of the types of ecosystem services, expressed as a score ranging from 1 to 10. Analysis of the figure shows that the highest score is given to nursery (8.71), followed by soil formation (8.43) and the water cycle (8.38). However, the population attaches less importance to salt mining, pharmacopoeia and animal husbandry, with respectively a scores of 7.15, 6.92 and 5.77 ( Figure 4 ).

The total economic value derived from fishing is estimated at CFAF 528,600,000 per year⁻¹ for the three villages, with CFAF 484,000,000 per year⁻¹ for Niodior, CFAF 36,200,000 per year⁻¹ for Dionewar and CFAF 8,400,000 per year⁻¹ for Falia ( Table 2 ).

The total economic value of processing fish and forestry products in the three villages is estimated at 45,161,000 FCFA.year⁻¹ with the highest value (22,300,000 FCFA.year⁻¹) recorded in Dionewar followed by Falia (11,475,000 FCFA.year⁻¹) and Niodior (11,386,000 FCFA.year⁻¹) ( Table 3 ).

The amount payable for fishing licences varies according to the type of licence:

Permit B, reserved for pirogue owners with canoes between 1 and 13 m long. They pay a fee of 15,000 FCFA.year⁻¹ per canoe.

Permit C, reserved for pirogue owners with canoes longer than 13m. They pay an annual fee of 25,000 FCFA⁻¹ per pirogue.

The fishing services station registers a total of 90 type B fishing licences and 55 type C fishing licences each year. The total monetary value generated by the granting of fishing licences for the three villages is estimated at FCFA 2,725,000 per year⁻¹. This total value conceals disparities within the villages, with the highest amount recorded in Dionewar (1,225,000 FCFA), followed by Niodior (950,000 FCFA.year⁻¹) and Falia (550,000 FCFA.year⁻¹) ( Table 4 ).

The total economic value of NTFPs is estimated at 20,607,000 FCFA.year⁻¹ for all three villages, with the highest value noted in Dionewar (9,320,000 FCFA.year⁻¹), followed by Falia (8,000,000 FCFA.year⁻¹) and Niodior (3,287,000 FCFA.year⁻¹) ( Table 5 ).

In total, salt production in the village of Niodior alone is estimated at 12,000,000 FCFA per year⁻¹ ( Table 6 ).

The total monetary value of agriculture is estimated at 8,100,000 FCFA.year⁻¹ ( Table 7 ).

The total monetary value of livestock production is estimated at CFAF 9,600,000 per year⁻¹ ( Table 8 ).

Revenue from firewood at Dionewar

The total monetary value of fuelwood is estimated at 6,000,000 FCFA.year⁻¹ ( Table 9 ).

Incomes from shipping (pirogue operators)

There are a total of 04 shuttles, called “couriers” by the inhabitants of the three villages. The pirogue boats run the shuttles throughout the week, with an average of 2 trips per day and 35 passengers per pirogue per day. Prices vary from 350 to 1000 FCFA. The total monetary value of navigation is estimated at 66,977,500 FCFA per year⁻¹ ( Table 10 ).

A total of 08 straw huts were found along the shores of the villages of Dionewar and Falia, run by local people to accommodate tourists. The monetary value of tourism was estimated at 60,840,000 FCFA.year⁻¹, with the highest amount recorded in Dionewar (47,160,000 FCFA) and the lowest in Falia (13,680,000 FCFA) ( Table 11 ).

Carbon sequestration

Land use in the AMPS is dominated by aquatic environments (freshwater and marine) (85.09%), although the uses and activities are not comparable between the different environments, the marine environment being largely represented. This is followed by mangroves (8.24%), savannahs (4.58%) and tannas (0.86%). Crops occupy the smallest area (0.001%). Thus, the total monetary value of carbon sequestration in the AMPS is estimated at 1,450,105,563 FCFA.an⁻¹ with 796,004,963 FCFA.an⁻¹ for mangroves, 604,872,963 FCFA.year⁻¹ for savannahs (trees and shrubs) and 49,227,637 FCFA.year⁻¹ for forests ( Table 12 ).

The estimated monetary value for the moderation of the effects of violent winds by the mangrove ecosystem of the AMPS was 16,680,000 FCFA.year⁻¹ for all three villages. The highest value was recorded in Niodior (10,800,000 FCFA.year⁻¹), followed by Falia (1,280,000 FCFA.year⁻¹) and Dionewar (4,600,000 FCFA.year⁻¹) ( Table 13 ).

The monetary value of the AMPS mangrove ecosystem for protection against coastal erosion and flooding is estimated at 270,800,000 FCFA.year⁻¹ within the three villages. The village of Dionewar has the highest value at 164,000,000 FCFA.year⁻¹ ( Table 14 ).

Analysis of Table 15 shows that the total monetary value of support services is estimated at 276,000,000 FCFA.year⁻¹, most of which (247,000,000 FCFA) comes from Financial and Technical Partners (FTPs) who finance conservation, restoration and processing activities.

The total economic value of the ecosystem services provided by the AMPS is estimated at 2,808,323,563 FCFA.year⁻¹. This value is separated into use values, which contain the highest regulatory services, estimated at CFAF 1,737,585,563.year⁻¹ (61.87%), provisioning services, estimated at CFAF 632,793,000.year⁻¹ (22.53%), and cultural services, estimated at CFAF 161,945,000.year⁻¹ (5.77%). The non-use values include only support services estimated at 276,000,000 FCFA.year⁻¹ (9.83%) ( Table 16 ).

This study shows that the majority of stakeholders (48%) are fishermen who ply their trade in the AMPS. Fishing is the main activity in the Dionewar municipality, and most of the young people in the municipality are involved in this activity. At AMPS level, we find the following players: fishermen, women who process fishery and forestry products, NTFP gatherers, firewood collectors, hoteliers, carters, fishmongers, salt producers, honey producers, breeders, farmers, ice-cream sellers, crate hirers, outboard mechanics and resellers who make a profit from the AMPS. The latter contribute to the management of AMPS resources. These results corroborate those of FALL [21] , for the Saint Louis AMP, where all these actors are found. In addition, women, who represent 29% of stakeholders, are much more active in the processing of fish and forest products. These results corroborate those of NDIAYE et al. [22] for the Kayar MPA, where 23% of women are involved in processing. According to a study by DEME [23] , more than 80% of the fish and forest products processing sector is managed by women.

This study shows that the entire population of the Dionewar municipality is aware of the AMPS. The population’s knowledge of the AMPS is obvious because the Dionewar is a peninsula located within the AMPS. In addition, almost all the inhabitants of the Dionewar municipality gave a higher score (8.71/10) to the nursery of fish species. This is due to the fact that fishing is the main activity in the area and, according to them, the mangroves are a breeding ground for fish. This result corroborates that of HAMID [9] in the Banc d’Arguin-Mauritania National Park, where people gave a score of 9.10/10 to the nursery. In fact, all the respondents gave good scores to soil formation (8.43/10) and the water cycle (8.38/10) because, according to them, soil and water support all the other existing services, as shown by HAMID [9] in the Banc d’Arguin-Mauritanie National Park. However, this dependence of the population on mangroves has been shown by DIOP et al. [24] in the Delta du Saloum National Park in Senegal.

The regulating services estimated at 1,737,585,563 FCFA.year⁻¹ are the most important ecosystem services offered by the AMPS. This result is due to the fact that the AMPS has mangrove ecosystems as well as tree and shrub savannahs and forest that sequester a significant amount of carbon also playing an important role in protecting against coastal erosion and flooding and moderating violent winds. These results corroborate those of SALL [25] for the Gandoul.

Marine Protected Area (AMPG), where regulatory services are more important, estimated at FCFA 5,203,055,447 per year⁻¹. In addition, the total economic value of fishery products in Dionewar fell from 982,732,100 FCFA.year⁻¹ in 2017 to 528,600,000 FCFA.year⁻¹ in 2023, a decrease of 454,132,100 FCFA.year⁻¹ [15] . This decline is due to the destruction of the mangrove ecosystem, the increase in the number of fishermen in the area, the effects of climate change and the abandonment of fishing by many young people because of illegal emigration. These results corroborate those of NDIAYE et al. [22] , who found the same reasons (destruction of mangroves, increase in the number of fishermen, etc.) for the decline in fish products in the Kayar MPA. In addition, supply services estimated at CFAF 632,793,000 per year⁻¹ are also important in the AMPS, helping to achieve food security and increase people’s incomes, thereby enabling them to improve their living conditions. These results are in line with those of SALL [25] for the AMPG and the Palmarin Community Nature Reserve (RNCP), and those of BADIANE et al. [26] ; DIEDHIOU et al. [27] for the Abéné MPA, where provisioning and regulating services have the highest economic value. In addition, these same studies have been carried out in many MPAs in Senegal, such as the Aire Marine Protégée de Gandoul (AMPG), the RNCP by SALL [25] and in the AMPS by MBODJ [15] . The same work has also been carried out in the sub-region of Mauritania, in the Banc d’Arguin National Park by HAMID [9] and in the mangroves and associated forests of the Douala-Edéa coastal landscape in Cameroon by NOUMEYI [4] . The total economic value of the ecosystem services provided by the AMPS estimated at 2,808,323,563 FCFA.an⁻¹ is much higher than that found 1,102,474,400 FCFA.an⁻¹ by MBODJ [15] . This is due to the fact that he estimated only the direct use values of the AMPS, whereas the present study focused on all the values (use and non-use). This total economic value is much lower than that found by FALL [21] for the Saint Louis MPA, estimated at 13,395,318,050 FCFA.year⁻¹. This is due to the fact that Fall’s sample was larger than ours because the Saint Louis MPA encompasses more than 08 villages that act directly on the MPA’s resources whereas at the AMPS level, only three villages benefit directly from the AMPS. Given the total economic value of the ecosystem services provided by the AMPS, the latter still deserves to be better protected.