Valuation of coastal ecosystem services in the Large Marine Ecosystems of Africa
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.
Section snippets
Estimated surface area of coastal marine habitats
The files digitizing the surface areas of coastal marine habitats targeted in this study (coral reefs, mangroves, and seagrass beds) are available on the Ocean Data Viewer database (available online at data.unep-wcmc.org). At the same time, we retrieved the distribution of kelp forests from Blamey and Bolton (2018). We determined coral reefs' surface area (UNEP-WCMC et al., 2018) considering only the surface areas that correspond to the African waters with the function “cutting” of the QGIS
Surface areas of coastal marine habitats
Based on our mapping, the combined extent of coral reefs, mangroves, and seagrass beds was estimated at approximately 117,000 km2, following a heterogeneous distribution. Seagrass beds, which are present all along the coasts of Africa, are the most extensive ecosystem with an estimated surface area of more than 72,000 km2 (Table 2). The mangroves come next, with a surface area of 27,465 km2, distributed between Mauritania in the north and Angola in the south for the Atlantic coast, while they
Discussion
Assessing the value of ecosystem services is essential to facilitate the dialogue with and between decision-makers and make choices about public investment. It helps to formulate sound policies for both economic development and nature conservation.
The first key outcome of the valuation is that coral reef is the most important habitat, with 72% of the value generated (17% from seagrass beds, 11% from mangroves, and 0.06% from kelp forests). Despite a surface area fourfold smaller than seagrass
Conclusion
As human populations continue to increase, particularly in Africa, future population growth and expansion of human settlements in the coastal areas will increase the challenges for conserving species-rich LMEs and maximizing the benefits that humans can gain from nature (Luck, 2007). With an annual loss estimated at 570 billion USD, it questions the effectiveness of policies at national, regional, and continental levels. Therefore, it is crucial to identify economic policy instruments for LMEs’
CRediT authorship contribution statement
Ewan Trégarot: Conceptualization, Methodology, Formal analysis, Writing - original draft, Writing - review & editing, Writing - review & editing. Grégoire Touron-Gardic: Conceptualization, Writing - original draft, Investigation, Formal analysis, Visualization. Cindy C. Cornet: Methodology, Formal analysis, Writing - original draft, Writing - review & editing, Writing - review & editing. Pierre Failler: Writing - review & editing, Supervision.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.Large Marine Ecosystems (LMEs) and the additional region of Africa Populationa Population Densitya* [inhabitants/km2] Population Growth Ratea [%/year] Habitat Functionality Index African Islands of
Acknowledgements
We are grateful to the anonymous reviewers for critical and constructive feedback.
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