Coastal ecosystems are essential for maintaining human well-being and global biodiversity. These ecosystems provide many benefits and services that contribute to climate regulation, such as erosion protection, hydrological regimes, flood risk reduction, and water purification (Saintilan et al., 2018; Sutton-Grier & Sandifer, 2019). In addition to these ecosystem services, coastal wetlands also provide an ecosystem service, often ignored or poorly considered for in ecological analyses, namely sequestration and storage of carbon dioxide (CO2) captured from the atmosphere and ocean(Chmura, 2013; Herr et al., 2017; Howard et al., 2014), aka coastal blue carbon.
"Blue carbon" is the carbon stored in the biomass and sediments of tidal marshes, mangroves and seagrass beds. These coastal ecosystems sequester greater amounts of carbon than those stored in terrestrial ecosystems (McLeod et al., 2011). Despite their important role in carbon sequestration, coastal ecosystems are increasingly affected by climate change factors, such as rainfall and temperature and human activities including population growth, environmental pollution, and land use/cover change (Lovelock & Reef, 2020; Ward, 2020). The loss of area in these ecosystems means that stored carbon is being released and that LULC changes or other disturbances to these systems are causing them to lose the future potential to store more carbon (Pendleton et al., 2012). In Morocco, the main estuarine wetlands have been protected by the Ramsar Convention on Wetlands of International Importance. But LULC changes are threatening coastal ecosystems, which are becoming sources of carbon emissions.
Where these wetlands are pressured from land-use, the sediments are exposed to the atmosphere or water, causing carbon stored in the sediments to bind with oxygen from the air to form CO2 and other greenhouse gas (GHGs) that are released into the atmosphere and ocean (Donato et al., 2011; Fourqurean et al., 2012; Howard et al., 2014). These activities lead not only to CO2 emissions, but also to losses of biodiversity and essential ecosystem services.
In this research, we used the InVEST model, an open-source tool available at www.naturalcapitalproject.org, among others (Arkema et al., 2013; Clerici et al., 2019; Sathiya Bama et al., 2020; Sharp et al., 2014) to quantify the value of CBCS service provided by coastal ecosystems by analysing changes in carbon storage over time in response to LULC changes. We conducted the case study in MBL located in northwest Morocco, to make a detailed accounting of blue carbon over the period (1971-2020) and to assess the potential LULC changes effects on the spatial and temporal dynamics of the CBCS. The InVEST model was used to analyse disturbances of coastal ecosystems caused by climate change and anthropogenic activities (Harley et al., 2006). Analysing these disturbances was important for prioritizing strategies to mitigate and adapt to climate change based on conservation and management of these ecosystem services. On a global scale, several coastal management strategies (Duarte, Losada, et al., 2013; Sutton-Grier & Sandifer, 2019; Wu et al., 2020) have been designed for the conservation (restoration and protection) of coastal ecosystems just as the United Nations Framework Convention on Climate Change (United Nations Framework Convention, 1992), in its article 4.1(d). Integrating these strategies into policies and funding mechanisms, which are still under development, can be a powerful tool for effective coastal management.
Therefore, the aims of this paper are: (1) to determine the historical extent of coastal ecosystems with accurate mapping, (2) to monitor carbon stock changes over five decades (49 years), (3) to quantify carbon stored and sequestered by coastal wetlands based on LULC changes, and (4) to estimate the monetary value of the CBCS provided by coastal ecosystems.The results of our valuation analysis highlight the economic importance of the CBCS service which offers an opportunity to mobilize additional funds and revenue by respecting the 2030 Agenda for Sustainable Development Goals (SDGs). The SDGs directly concerned are, respectively, climate action (goal 13) and life on land (goal 15) (www.unfoundation.org) which aim to: take urgent action to combat climate change and its impacts, halt and reverse land degradation, and halt biodiversity loss.