JCBPS; Section D; August 2020 –October 2020, Vol. 10, No. 4; 362-376. E- ISSN: 2249 –1929 [DOI: 10.24214/jcbps.D.10.4.36276] Journal of Chemical, Biological and Physical Sciences An International Peer Review E-3 Journal of Sciences Available online atwww.jcbsc.org Section D: Environmental Sciences CODEN (USA): JCBPAT Research Article Physical factors limiting the success of mangrove restoration policies in the Biosphere Reserve of the Saloum Delta, Senegal 1,2 1 2 El Hadji SOW , Taibou Ba , Boubou Aldiouma SY 1Centre de Suivi Ecologique, Rue Léon Gontran Damas, BP 15532, Fann Résidence-Dakar, Sénégal, 2Laboratoire Leïdi «dynamiques des territoires et développement», Université Gaston Berger, Saint- Louis, Sénégal, Received: 18 August 2020; Revised: 30 August 2020; Accepted: 06 September 2020 Abstract: The mangrove ecosystem of the Biosphere Reserve of Saloum Delta (RBDS) presents a variety of ecological and socio-economic interests. However, this ecosystem continues to be continuously degraded despite numerous restoration programs that have been underway for more than two decades. Several actions have not produced satisfactory results. Therefore, in addition to socio-economic factors, it is also necessary to evaluate and analyze the physical factors that hinder the success of these mangrove restoration policies in the RBDS. To this end, the scientific approach adopted integrates a literature review and field work that involves in situ measurements of water salinity and acidity, and sedimentation. The results show that high salinity levels in several reforestation plots hamper the survival of seedlings. In addition, the silting noted in some plots transforms the soil texture, making mangrove regeneration difficult. Keywords: mangrove, degradation, politics, restoration, physical, Saloum delta INTRODUCTION Senegal's mangroves are the most northerly in West Africa and constitute a valuable ecosystem for biodiversity conservation. Most of the lagoons, estuaries and delta are populated by mangroves which extend over an area of about 200,000 hectares [1]. These mangrove populations, sources of many natural resources (firewood and services, oysters, arches, fish, etc.) but also an important breeding 362 J. Chem. Bio. Phy. Sci. Sec. D ; August 2020 –October 2020, Vol. 10, No. 4; 362-376. DOI:10.24214/jcbps.D.10.4.36276.] The Limiting … El Hadji SOW et al. ground for many fish species, play a socio-economic role (food, shellfish exploitation, fishing, etc.) and ecological (windbreaks, species reproduction and refuge area, sediment fixation, etc.) for the Sine Saloum natural region [2,3]. The mangrove therefore occupies an important place in the natural environment and biodiversity. It is also essential for the life of the local populations who maintain a close relationship with it. However, the degradation and decrease of the Senegalese mangroves is accentuating due to the decrease in rainfall recorded since the 1970s, illegal exploitation by local populations, and other factors having a negative effect on the resources needed to the life and economic activities of local populations (forest, fishery and tourism resources) as well as environmental degradation. The Saloum Delta Biosphere Reserve (RBDS) is facing this degradation process. It is located in the center-west of Senegal in the natural region of Sine Saloum, between 13 ° 35 and 14 ° 15 North latitude and between 16 ° 03 and 16 ° 50 West longitude. It covers an area of 234,000 ha and combines the characteristics of a marine, estuarine, lacustrine and marsh wetland, and its various sites fulfill the classic functions of a wetland. It is located on the Senegalese coast about 150 km south of Dakar (Figure 1). The Saloum, which functions as a reverse estuary [4], is a veritable arm of the sea [5] bordered by vegetation characteristic of coastal areas, in this case the mangrove. The Saloum is home to the northern margin of the Southern Rivières mangrove [6, 2,3]. Along the banks of the Saloum delta stretch leashes and shallow seas. The delta's countless tree channels that are sensitive to the tide, grow into islands, and are bordered by mangroves on both shores. Vast mudflats and dense and varied vegetation form an ecosystem ensuring biodiversity. Mangroves also green on the lowlands of the continental parts of the delta and behind these green parts develop sulfuric soils called "tanne". The RBDS is placed in the bounded zone of the isohyet lines between 700 and 900 mm. According to data recorded from 1918 to 1993, annual precipitation shows a decreasing trend from 1968. On the other hand, especially for the decade from 1980 to 1990, annual precipitation is low and remains at the very low level of 400 at 600 mm. However, they have resumed a rise to the normal level since 1999 [1]. The altitudes of the region do not exceed 40 m and are marked by a weakness of the slopes which explains the deep rise of the sea and a predominant marine influence. The tides are sensitive up to more than 100 km inland. The salinity there is very high (greater than seawater estimated at 35g / l) and is a limiting factor for the development of vegetation [7]. In this area, the mangrove ecosystem constitutes the main source of income for the populations. However, a state of continuous degradation of this mangrove in the RBDS is observed despite its restoration policies initiated and adopted since the end of the 1990s and the beginning of the 2000s. Various mangrove preservation and restoration programs have been undertaken. , initiated by local populations, the State, various donors and NGOs. Among these initiatives, we can mention those of the West African Association for Marine Environment (WAAME), the International Union for the Conservation of Nature (l’IUCN)[8], the Oceanium, the World Wide Fund for Nature (WWF) , Wetlands International Africa (WIA), Aide au Développement Gembloux[9], etc. To these programs are added those coordinated by the Directorate of National Parks (DPN), the Directorate of Community Marine Protected Areas (DAMPC) and the Directorate of Water and Forests, Hunting and Soil Conservation (DEFCCS) [2, 3, 10] In this context, a number of political development orientations have been recommended and implemented. Among the latter is the establishment of biological rest and rotation in the collection of marine invertebrates. Added to this is the establishment of an institutional framework to ensure sustainable management of renewable resources and ecosystem restoration (reforestation and / or 363 J. Chem. Bio. Phy. Sci. Sec. D , August 2020 –October 2020, Vol. 10, No. 4; 362-376. DOI:10.24214/jcbps.D.10.4.36276.] The Limiting … El Hadji SOW et al. assisted natural regeneration) which aims to restore degraded environments (for example) man and / or nature) in their initial natural state. Despite everything, mangrove degradation is still a thorny issue in the RBDS. In this context, the objective of this contribution is to study the physical factors limiting the success of mangrove restoration policies and programs undertaken in the RBDS. The study focused on the analysis of the environmental conditions that hinder the success of mangrove restoration actions in the area. Figure 1: location of the Saloum delta biosphere reserve MATERIALS AND METHODS 1. Data: In order to have data on the situation of sediment dynamics but also on the salinity and acidity of the water at the mangrove reforestation sites of the RBDS, a documentary review was carried out. In addition, series of field measurements were carried out in 14 reforestation plots. The data collected relate to in situ measurements of the following parameters: change in the level of siltation, electrical conductivity (EC) and hydrogen potential (pH). The objective of these measurements is to understand the level of these parameters and their impact on young plants because it must be understood that the level of acceptability of mangroves for these physicochemical parameters is limited to certain thresholds. 2. Methods 2.1. The choice of experimental plots: There are 14 selected plots spread over 09 sites, 06 of which are partly land and 03 partly insular. The choice of sites is justified by their geographical distribution at the RBDS level, the level of intervention of projects and / or NGOs at said sites and the presence of reforested plots less than 7 years old. Thus, the plots are located in the villages of Djirnda, Baout, 364 J. Chem. Bio. Phy. Sci. Sec. D , August 2020 –October 2020, Vol. 10, No. 4; 362-376. DOI:10.24214/jcbps.D.10.4.36276.] The Limiting … El Hadji SOW et al. Moundé and Dionewar (island part), Bangalère, Keur Mbar, Néma Bah, Gagué Mody and Mbassis (mainland). 2.2. Measurement campaigns: Two measurement campaigns were carried out: in the dry season (from 01 to 05 May 2018) and in the rainy season (from 20 to 25 September 2018). These two campaigns made it possible to collect the targeted data during two different seasons. The period covering the duration of monitoring of these plots is one (01) year. The aim here is to follow the evolution of these parameters between two seasons in order to better understand their effects. 2.2.1. In situ measurements of the intensity of sediment dynamics: In the framework of this study, the stake method (sighting stations) was used. This network of stakes was used to quantify soil inputs / losses (deposition / erosion) expressed in height and determined from the natural change in the level of the soil surface. This quantification is calculated on the basis of the balance sheet of fluctuations in ground level from an initial state taken as the origin. This measurement method was applied in 10 experimental plots reforested with mangrove (Djirnda, Baout and Moundé (island part), Gagué Mody and Mbassis (land part). In each plot the 1 m stakes are half-driven (50 cm). Thus, 02 series of lifting four months apart were operated (May and September 2018).