Development Prospects of the Mangrove Relic of Foulpointe—East Madagascar

Located about fifty kilometers North of Toamasina (East Madagascar), the Commune of Mahavelona Foulpointe has a mangrove relic of about 2 hectares. Despite the ecological and socio-economic roles played by this ecosystem, it remains so far an orphan site, both in terms of official management and development. The purpose of this article is to take stock of the situation with a view to proposing methods for the sustainable development of this small mangrove via valuation of its natural dynamics. Systematic floristic inventory work was carried out, following a linear ABC transect of 50 100 m, from the sea (zone C) to the rear mangrove (zone A). Five mangrove species exist at Foulpointe: Avicennia marina, Sonneratia alba, Bruguiera gymnorrhiza, Rhizophora mucronata, Lumnitzera racemosa. With anthropogenic harvesting and tourism activities in the area, this ecosystem suffers an annual spatial loss of about 0.14 ha between 2009 and 2016. With a natural regeneration rate of about 966% the small mangrove has a strong capacity for regeneration. Taking into account the pace of current clearing, it would disappear in 10 15 years. The valorization of regenerated young plants, followed by intensive preservation and restoration actions, constitutes a sustainable development path.


Introduction
With 4260 ha of mangroves [1], the Malagasy East coast accounts for nearly 2% of Malagasy mangroves [2]- [8]. Described as small mangroves [8] for the most part, these forests are mainly found at the Ambodivahibe, Irodo and Rigny complex, where 84% of the mangroves in the East of Madagascar are concentrated [1] [9]. About 2 hectares in size, the mangrove relic of Foulpointe, a rural commune located about fifty kilometers north of Toamasina (Figure 1), represents only 0.08% of the mangroves of the East. Despite its small size, this ecosystem plays important socio-economic and ecological roles as raised by [10]. Indeed, mangroves are still an important ecological niche for the food and financial resources of the riparian population [11] [12]. As small as these, they must be considered in the same way as other development factors [1]. However, the mangrove relic of Foulpointe remains unknown; it is an orphan site in terms of official manager and planning. Its ecological potential is not acknowledged because of the lack of investigation to this end. Thus, this article aims to identify the ecological and development potentials of this small mangrove. The objective is to propose a modality of sustainable management through the valuation of its natural dynamics, by combining restoration and actual involvement of the local population.

Materials and Methods
Systematic floristic inventory work was carried out in plots of 10 m × 10 m. The objective is to identify the different mangrove species and associated plants present in the surveys, their regenerative capacity and their distribution along a linear transect ABC ( Figure 2) perpendicular to the shore, from the sea (zone C) to the back mangrove (zone A), over a distance of 50 -100 m. In addition to identifying the vernacular and scientific names of the inventoried plants, the following parameters have been recorded: • Relative abundance A of each species such as:   if r > 1000%: very strong regeneration if 300% < r < 1000%: strong regeneration if 100% < r < 300%: medium regeneration if r < 100%: weak regeneration • The pH, the C/N ratio and the salinity of the water, which were measured in situ using a handheld multiparameter quality monitoring system horiba u-20 series u-22.23.

A Mangrove Relic Dominated by Avicennia marina
The following 5 mangrove species can be found at Foulpointe: Avicennia marina, Sonneratia alba, Bruguiera gymnorrhiza, Rhizophora mucronata and Lumnitzera racemosa. Figure 3 shows their relative abundance, with a negligible percentage for Lumnitzeraracemosa. First, Avicennia marina predominates everywhere, with an abundance of 87%, followed by Sonneratia alba and Rhizophora mucronata which have a respective abundance rate of 8% and 3%. Finally, the whole site contains very few individuals of Bruguierra gymnorrhiza, which account for only 2% of the total number of mangrove stocks recorded.

Associated Species Upstream and Downstream
Other than the few Avicennia marina trees which are 360 individuals. ha −1 , the upstream part of the mangrove of Foulpointe is occupied by associated species withstanding ecological conditions relatively identical to those of mangroves.
The following species are thus visible in zone A: Phymatodes scolopendria which is a lizard-legged fern, Typhonodorum lindleyanum which is a typical species of eastern Madagascar swamps (species native to Madagascar, Comoros, Mauritius and Zanzibar, according to [14]), Cyperus sp., a species acclimated to wetlands, as well as Terminalia cattapa, a tree native to New Guinea that has naturalized in

A High Regeneration Capacity
With a regeneration rate of 3615%, zone A, located at the inner limit, has a high regeneration potential, according to the Rothe scale [13]. The other two zones B and C respectively record high rates of 819% and 929%. In all, the entire mangrove relic of Foulpointe regenerates well if one refers to its overall regeneration rate of the order of 966%.

Cutting Traces Left by Local Residents
Cuttings of Avicennia marina and Sonneratia alba mature trees are visible, from upstream to downstream, at the level of the 3 zonings. In total, 48 trees·ha −1 were felled by residents in 2016 for construction and service wood. 21% of harvestings are taken at the inner limit of the mangrove (zone A), while 62% and 17% are concentrated respectively inside (zone B) and on the maritime border (zone C).

Gateways for Anthropogenic Pressures
With anthropogenic harvests and tourism activities in the zone, this ecosystem suffers an annual spatial loss of about 0.14 ha between 2009 and 2016, a low for-  These openings are not only subject to regular trampling by mangrove users, but they are also a factor of disturbance, or even destruction of the seedlings along these trails. Access to mangrove lots becomes easier with these openings.
• Fishing for crabs and other invertebrates, which encourages fishermen to penetrate deeper into the mangrove, causing losses in regeneration due to the use of basket traps and the trampling of seedlings by fishermen.
• Open defecation, the practice of which remains current for nearly 10% of the riparian people surveyed. The dumping of liquid and solid waste, as well as the lack of adequate sanitation infrastructure for urban roads could affect the resilience of Foulpointe mangroves.

Possibility of Maintaining or Even Extending the Current Area
Taking into account the current pace of clearing, in the lack of a preservation policy and in the event of disruption of the natural regeneration dynamics, the small mangrove of Foulpointe would disappear in the next 10 -15 years. However, the station conditions of this ecosystem, like the salinity of water and soil, the exposure to tides, as well as the zoning typical of other Malagasy mangroves, would be favorable indicators for the installation, development or even spatial extension of the current relic. The absence of Ceriops tagal in Foulpointe mangrove would indicate the existence of a shadier forest environment after predominance of an association Rhizopora mucronata and Bruguiera gymnorrhiza [  Non disturbance of the natural plant succession mechanism is one of the recommended methods to maintain or increase the area of the current relic.

Passive Restoration in the Mangrove and Active Restoration on the Mainland
The valuation of young regenerated plants, followed by intensive preservation and restoration actions, constitutes a sustainable management path for the man- woods depends on the existence of woody sources other than mangroves [17], the balance could be maintained in favor of mangroves thanks to the existence of wood from the mainland. For the case of Sainte Marie, the presence of Grevillia banksii, Eucalyptus sp. and Melaleuca quinquenervia on the mainland, near the riparian villages of the mangrove lots is one of the preservation factors of the mangroves of the island [26]. Hence the low utilization rate of 3% of mangrove wood in construction in Sainte Marie, against 66.7% to 87.5% in the Tsiribihina delta, in the southwestern part of Madagascar [17].
Here are some accompanying measures to ensure success of a passive restoration: •

Clear Responsibility of the Stakeholders
Being a popular tourist site in the Atsinanana Region, Foulpointe has a certain number of assets to sustainably preserve its mangrove relic. The existence of a municipality will in this direction was felt during the interviews conducted with the local council leaders. It is therefore clear that the effective involvement of the population and the valuation of the natural regeneration mechanism could be an effective way to preserve and enhance this relic. But the real strategy is to clarify the roles and responsibilities of those in charge of relic management. The table gives an outline of the charter of responsibilities of the stakeholders likely to be

Conclusions
The interest of this study lies in: • The knowledge of the Foulpointe mangrove forest, which until now remains little known in terms of structures and pressures, two basic details that are essential for its sustainable development and management. • The "renaturation" of the site through a natural approach favoring regenerations and the natural reconstitution process.
• The safeguarding of a micro-ecosystem which, despite its small spatial extent, requires the effective and clear involvement of a certain number of users and stakeholders. Clarification of the roles and responsibilities of the latter is a key to the successful management of the current forest relic.
• The existence of a number of ecological stress indicators for certain species such as Lumnitzera racemosa and Bruguiera gymnorrhiza. If these species have difficulty settling on site, Ceriops tagal is absent due to unsuitable ecological and anthropogenic conditions, making the plant succession process incomplete.  • Preliminary feasibility study of the implementation of the development plan and technical-legal support • Facilitation of the official implementation of the management plan for the current mangrove lots • Implementation of certain accompanying measures such as the issuance of the required administrative authorizations, capacity building of the stakeholders, legal-administrative follow-up and monitoring , strengthening and implementation of the national policy for the fight against wildfires and illegal clearings Private economic operators or other stakeholders beneficiaries of ecosystem services (hotel owners, schools, associations, tour operators) • Compliance with the rules governing the use of the site ,object of management • Technical and financial contribution in the site management, via payment of rebates, taxes and access fees • Implementation of some accompanying measures such as capacity building of the beneficiary stakeholders' staff in terms of environmental education, promotion of sustainable ecotourism at the Foulpointe mangrove lots via the development of an adapted advertising policy, participation in the planned reforestation works on mainland