The densely populated and lowly elevated coastline of the Gulf of Guina is particularly exposed to coastal erosion and sea-level rise. The entire coastline is currently experiencing alarming erosion rates, ranging from 1 to 15 meter per year between Côte d’Ivoire and Nigeria, mostly because of human activities. The problem is well studied and various programs aim to put in place coastal protection measures. By contrast mid- and long-term vulnerability to sea-level rise triggered by climate change has received less attention in this region. 

In addition, to assess the various risks induced by sea-level rise, it is also necessary to consider land surface movements. The gradual lowering of the land surface in some places is called subsidence. The phenomenon is widespread at the global scale, especially in coastal megacities and deltas: 51 to 71% of present-day relative sea-level rise experienced by people worldwide is actually caused by subsidence. The rate can reach several centimeters per year in some places, however coastal subsidence is globally critically under-quantified, and the Gulf of Guinea region is no exception to this.

This research program aims to fill the lacune in knowledge on coastal land subsidence and relative sea-level rise along the Gulf of Guinea. It will provide useful space-borne quantifications of current coastal subsidence rates, assess the driving forces of land subsidence and provide first projections of potential future subsidence using numerical models. 

Impact will further be created by collaborating with local institutes, connecting to other projects and disseminating findings, data and tools to local stakeholders. 

One of the long-term objectives is also to create awareness and agenda setting of this issue of relative sea-level rise in the region, in order to support sustainable development or adaptation projects in coastal areas and policymaking in the region. 

The first working group will assess current subsidence rates for the whole coastline, using satellite data to monitor vertical land movement over several years. The results will be combined to satellite elevation data to provide a first assessment of the areas that could be flooded in future decades. 

The second working group will focus on the city of Lagos and surroundings, to provide an in-depth analysis of subsidence and to understand drivers and processes. The research team will build a process-based numerical model of subsidence to provide projections of future subsidence rates according to different scenarios.

Then, the methods developed for Lagos will also be applied to 3 or 4 other areas, coastal megacities or deltas, identified as “hotspots” for relative sea-level rise by the first working group. 

Knowledge exchange events (seminars and workshops) will also be regularly organized, to disseminate research findings and build a regional community of interest on subsidence and relative sea-level rise. 

Results will be shared through scientific papers, technical reports, on-line databases and policy briefs. They will provide valuable information for policymakers and coastal (infrastructural) development projects potentially impacted by relative sea-level rise. In particular, results will help to better calibrate coastal adaptation measures and may also identify areas where the efficiency of natural coastal defences could fail in the future. Understanding the drivers of subsidence will also help to identify potential mitigation measures. The project will also foster public policy dialogue on coastal vulnerability, to favor adaptation projects.

Public actors need to monitor the state of the environment in order to assess the effectiveness of their actions, prioritize policies and management measures, and thus objectively establish their contribution to the conservation of natural capital. To do so, they must be able to rely on scientific standards enabling them to define the thresholds from which environmental functions can be considered sustainable.
The ESGAP (Environmental Sustainability Gap) is an innovative tool that assesses the state of a territory’s environmental functions and their level of sustainability. For all critical components of natural capital in the territory concerned (air or water quality, pollution, forest resources, fisheries, etc.), this indicator calculates the difference between their current state and a state that would be sustainable (that is, a state compatible with a sustainable functioning of the processes necessary for the preservation of life, human activities and well-being). This allows the calculation of an “environmental sustainability gap”, which highlights the path that remains to reach the stage of environmental sustainability. This can then serve as a guide for public policy to estimate and preserve the natural state of a given territory.

Within the framework of the ECOPRONAT research program, AFD wishes to develop methodologies for assessing strong sustainability, that is to say adopting demanding criteria concerning the non-substitutability of natural capital by other forms of capital (physical and other) in a territory or country. AFD would also like to promote their use in international settings and contribute to the emerging international standards on the good ecological status of ecosystems.

This project aimed to test the relevance of the ESGAP framework in developing countries, where not all data on natural capital are always available. In collaboration with the United Nations Environment Programme (UNEP), Paul Ekins' team at University College London (UCL) supported two pilots of this indicator in Vietnam and Kenya.

These pilots were carried out by teams of experts both from national research institutes responsible for monitoring and reporting environmental data: the Kenya National Environmental Management Authority (NEMA) and the Institute of Strategy, Policy on Natural Resources and Environment (ISPONRE) in Vietnam. This work enables better integration of strong environmental sustainability principles into global environmental assessments.

These pilots also sought to better document the challenges of strong environmental sustainability in the series of Measuring Progress reports published by UNEP.

The ESGAP framework is based on a dashboard that provides information on changes in the functional state of 23 components of the environment, focusing on the differences between these changes and the objectives of maintaining or achieving “good ecological status”. These components cover the four main categories of critical and essential environmental functions: the provision of resources, the reprocessing of pollution, biodiversity and human health. The scores of the 23 components are then aggregated to form a synthetic indicator and a dynamic indicator. 

The two pilots revealed the general lack of standards for maintaining biodiversity in both countries, as well as significant gaps in environmental regulation, both in Kenya and Vietnam. The lack of historical reference points to measure the good state of the environment is a serious obstacle to the establishment of protection policies and prevents the debate on narratives and development trajectories respectful of the natural heritage.

Moreover, the analysis shows a worrying situation in both Kenya and Vietnam about pollution of natural environments, despite the very limited availability of data on these issues. In Kenya, the results are rather good on natural resources, but many essential and critical contributions of natural capital to human well-being and health are greatly degraded, both for water and air quality, as well as for access to natural amenities. In Vietnam, fish resources, soil erosion, and air and water pollution appear to be the most degraded dimensions.

According to ISPONRE and NEMA, the ESGAP framework has great potential as a tool for communicating the state of a territory and for monitoring public policies in both countries. It offers a framework for broadening the range of topics covered by public policies and proposes a high-quality standard for the establishment of environmental sustainability assessment frameworks.

This research project also supported a flagship UNEP report on the environmental content of the Sustainable Development Goals (SDGs), Measuring Progress: Environment and the SDGs, which incorporates the lessons learned from these two ESGAP pilots. This has shown that, of the 231 SDG monitoring indicators, 77 can be linked to an environmental theme from near or far, but that only 11 of them really describe the state of the environment.

Download the reports: 

• Environmental Sustainability in Kenya: A Case Study in the ESGAP and SESI (June 2022)
• Environmental Sustainability in Vietnam: A Case Study in the ESGAP and SESI (June 2022)

Initial feedback indicates that the ESGAP pilots need to be backed up by real capacity-building exercises of the administrations in charge of environmental monitoring and natural capital management, in order to hope to improve environmental diagnostics in the long term.

The concepts of “scientific standards” and “diagnosis of the state of natural capital contributions” also need to be refined, explained and adapted to the available contexts and data: if, ideally, these standards are derived from international frameworks and legitimated at the national level, often alternative indicators must be used to adapt the standards to different contexts.

These lessons complement those from a pilot of the ESGAP indicator, led by AFD and WWF in New Caledonia. Following another ECOPRONAT call for projects, two more ESGAP studies are underway:

• A first study aims to develop indicators for biodiversity and the health of natural ecosystems, as well as an ESGAP methodology in South Africa and Colombia.
• A second study aims to refine socio-economic indicators and study the relationship between the economy and the environment, with Vietnam as a case study.