Valuation of coastal ecosystem services in the Large Marine Ecosystems of Africa

Abstract

The African coastline is bordered by highly valuable marine ecosystems, but the environmental degradation due to anthropogenic pressure alter the benefits that they render to people. Our paper aims at assessing the value of ecosystem services provided by mangroves, seagrass beds, coral reefs, and kelp forests present in the Large Marine Ecosystems (LMEs) of Africa. After the mapping of coastal marine habitats, our valuation relies on the transfer of value of all ecosystem services from reference monetary unit values, extracted from the literature. A habitat functionality index based on the assumption that a higher population density and a higher demographic growth rate lead to a decrease in the functionality and services of marine habitats was then defined and incorporated into the valuation. The surveyed coastal habitats cover about 117,000 km², with seagrass beds being by far the most extensive habitat. Present all along the coasts of Africa, their surface area represents about 62% of surveyed coastal habitats, followed by the mangroves (23%), coral reefs (15%). Kelp forests are only present in the southern Benguela Current LME. We estimated the annual value of the LME's coastal ecosystem services at 814 billion USD. Coral reefs have the highest value (588 billion USD/year), followed by seagrass beds (135 billion USD/year), mangroves (91 billion USD/year), and kelp forests (0.4 billion USD/year). The results show that ecosystem services from the four coastal habitat types had the highest value in the Agulhas Current LME, representing 38% of the total value, followed by the Red Sea LME (28%) and the Somali Coastal Current LME (10%). The three LMEs of the Atlantic side represent 15% of the total estimated value. Our paper highlighted many gaps that remain to be filled in terms of mapping and ecosystem services assessment in Africa. Nonetheless, our estimated values can facilitate dialogue between decision-makers and managers, and between countries sharing the same habitats and marine resources, toward better management of these ecosystems.

Introduction

The African coastline, which is over 30,000 km long, is subject to many pressures (UNEP-WCMC, 2016). Its natural habitats are damaged due to direct anthropogenic actions (resource extraction, environmental modification, pollution) and indirect actions such as climate change (Belle et al., 2016; CBD, 2018). Thus, the surface area of natural coastal habitats such as mangroves, coral reefs, and seagrass beds has globally decreased in recent decades (with an annual loss of mangrove surface area of 2%, for example) (IPBES, 2018). At the same time, the ecological condition of these habitats has deteriorated, leading to a loss of more than 50% of the live coral cover in coral reefs of the southwest Indian Ocean following the 1998 and 2016 bleaching events due to surface waters warming (Belle et al., 2016; IPBES, 2018). Therefore, African coastal habitats’ optimal functioning is hampered even though their functions are essential to maintain a suitable living environment for African and World populations.

In order to counteract this phenomenon, national and international institutions have mobilized to organize and harmonize public policies in favor of the coastal environment in Africa (Abidjan Convention, Nairobi Convention, Jeddha Convention, Convention on Biological Diversity, etc.). In this context, ecosystem-based approaches on a multi-national scale are becoming increasingly common. This is particularly true within Large Marine Ecosystem (LME) programs that often establish multi-national diagnostics and strategic documents to optimize resources and natural spaces management within large-scale geographical areas, but also to guarantee a stable regional base in terms of human, institutional and scientific capacities and progress towards sustainable development (Satia, 2016). While public policies formerly focused on maintaining natural spaces and related biodiversity, they are now increasingly included in the process of reclaiming and enhancing degraded natural areas (Palmer and Filoso, 2009; Prober et al., 2019; Smith-Hall, 2009), in line with the United Nations’ Sustainable Development Goals – SDG 15 (United Nations, 2015) and Aichi Targets 14 and 15 (CBD, 2010). In the current framework of the Intended Nationally Determined Contribution for the implementation of the Paris Agreement with particular consideration for blue carbon (UNECA, 2016; CMAE et al., 2019), or more conventionally in the achievement of Aichi Targets (Tittensor et al., 2014; Failler et al., 2019) and the implementation of Global Environment Facility (GEF)-funded programs related to LMEs (Sherman, 2019), the enhancement of coastal habitats has a leading role. In this regard, a monetary valuation is a relevant tool for integrating the environment into the economic, political, and social spheres (Binet et al., 2012; UNEP and GRID-Arendal, 2016). Quantifying ecosystem services in monetary terms allows us to compare different types of habitats and compare them with income-generating economic activities (Bacon et al., 2019). It also makes it possible to estimate the costs of political inaction (Trégarot et al., 2017), following the degradation of natural habitats. While the natural capital is often overlooked due to a lack of data compared to the human, social and economic capital (Failler et al., 2015; Pascal et al., 2018), this approach offers the advantage of emphasizing ecosystems in the planning of public policies. Choices in terms of investment for protection or conservation would be better informed if, for example, undervalued and previously overlooked habitats, such as seagrass beds, are taken into account. Monetary valuation of ecosystems further allows for greater balance in decision-making regarding the use of spaces: economic activities to the detriment of ecosystems versus risk-averse management of these ecosystems due to their high economic value.

This article's objective is to present an economic valuation of the services provided by African coastal ecosystems. The economic value of these ecosystems is calculated from the surface area of the main African coastal habitats, namely mangroves, coral reefs, seagrass beds, and kelp forests, and considers their functionality in relation to anthropogenic stressors. We used Large Marine Ecosystems (LMEs) as a spatial unit for conservation purposes. Developed by Sherman and Alexander (1986), “LMEs are relatively large areas of ocean space (>200,000 km²) located along the margins of the continents. They are defined based on four ecological criteria: bathymetry (bottom depth); hydrography (water column structure); productivity; and trophic linkages” (Sherman, 2019). The LME concept enables ecosystem-based management to provide a collaborative approach to managing resources within ecologically bounded transnational areas. The method used is innovative since it incorporates the level of anthropogenic pressure to adjust the monetary valuation calculated using benefit transfer, where monetary assessments are usually limited to surface area data. The adjustment of the production function, which characterizes relationships between habitat condition and the delivery of economically valuable ecosystem services, by the ecological condition or the vulnerability of habitats was tested in the evaluation of ecosystem services for coral reefs and associated habitats (mangroves and seagrass beds), within the French Initiative for the Protection of Coral Reefs in French Overseas - IFRECOR (Failler et al., 2015; Trégarot et al., 2017). It was more recently applied to assess ecosystem services in the Banc d'Arguin National Park (PNBA), the largest marine protected area in West Africa (Trégarot et al., 2018). In the context of chronic lack of data and studies relating to African coastal and marine ecosystem services (Wangai et al., 2016; Willcock et al., 2016), this article presents, to our knowledge, the first exhaustive monetary study at the scale of the whole African continent for four essential coastal habitats. The geographic scale is unprecedented, considering that none of the monetary assessments that have already been conducted in Africa does exceed the regional level (Interwies, 2011; Interwies and Görlitz, 2013 in UNEP and GRID-Arendal, 2016), or individual LME level (Chukwuone et al., 2009). Moreover, they focused on few topics such as fishery resources (Sumaila, 2016), West African marine protected areas (Binet et al., 2012) and carbon sequestration (Bryan et al., 2020). Our approach can be re-used for similar work at other spatial scales (regional, national and local), particularly within the framework of the implementation of the African strategy relating to the blue economy, within which the enhancement of coastal ecosystems is a central concern.

The article is structured in three parts to present 1) the methods used for mapping and assessing ecosystem services considering the anthropogenic pressures; 2) a section giving the estimated value of coastal habitats per LME; 3) a discussion that integrates the main results into a broader reflection on the development challenges of the continent with its coastal environment.