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.

Despite a renewed interest for the notion of “commons” within the academic world, little work has been done about land and housing issues in cities of the Global South.

Yet access to urban land is a major issue for dwellers of these rapidly growing cities and a determining factor for the improvement of their living conditions and for their access to “adequate housing”, according to UN terminology. The mainstream approach to urban land tenure, based on full individual private ownership and the free market, generates speculation and land grabbing, and exclusion of the most precarious households.

The critical dimension of the commons notion opens up innovative ways to produce housing in the Global South, according to plural perspectives that take into consideration the inhabitant’s needs and their agency abilities.

This research project aimed to highlight the diversity of hybrid, permeable, evolving commons within space and time.  These commons aim at getting and securing access rights to land and housing and associated services, which often arise from unexpected opportunities.

The research team looked at innovative ways of holding land: commonly held, with a housing function and in a nonspeculative perspective (when the transfer of land is carried out according to a framework decided beforehand by a community, without any capital benefit).

The methodology was based on case studies in developing cities:

• The first phase of the study (2017-2018) led to three field surveys in Burkina Faso, Kenya and India.
• The second phase (2018-2020) consisted of two additional field surveys (Brazil, Mexico), as well as the follow-up of the work carried out in New Caledonia by students in the framework of the School of Urban Affairs (Master’s Degree « Urban Planning Cycle») of Sciences Po Paris.

The team consisted of:

• An academic with authorization to supervise research (HDR), who directed the study;
• A research engineer, who provided the scientific coordination of the study;
• Local researchers specialising in land and urban issues in survey countries.

The study consisted of five phases: documentary research, field research, data processing, drafting of deliverables, valorisation of  research findings. 

This research project resulted in the publication of several research papers:

• “Land-based commons for inclusive cities” (available in French): this research paper presents the conclusions of 8 case studies, focused on securing popular habitat through shared ownership of the land.
• “Does Mexico’s social land still bear commons?” (available in French): Mexican common land has undergone major transformations since the 1990s. This research paper presents the study on the outskirts of the metropolitan area of Mexico City led by the students of the Urban Planning Programme of Sciences Po Paris, under the supervision of Jean-François Valette.
• “Regularizing Rio favelas through land pooling?”: the paper sheds light on an original system of collective land regularization in precarious neighborhoods, which puts into practice the notion of “plural property” running through Brazilian law, and which defends the right of the inhabitants to remain in place.
• “User cooperatives in Uruguay: the challenge of housing as common” (available in Spanish)

The final report of the research project on urban land-based commons for housing in the Global South can be downloaded here.

All the publications and events related to the research project are listed on the following website: Communs fonciers pour l’habitat – Quelle contribution à l’inclusion urbaine dans les Suds ? (hypotheses.org)

"The commons can be understood as a social policy of housing, offering access to housing to the most vulnerable social categories. Moreover, they can provide an alternative path to classical public housing policies which favor individual private property. Indeed, even though these initiatives emerge from dwellers organizations, they might be supported and framed by national governments. Often acknowledged, supported and even presented as standard to be followed, the commons have drawn increased attention recently from dwellers federations, associations, NGOs and international institutions that document their functioning and contribute to the international circulation of these alternative ideas." (Simonneau & Denis, 2021)

• Claire Simonneau, professor and researcher at Université Gustave Eiffel and researcher at the Laboratoire Techniques, territoires et sociétés (LATTS)
• Stéphanie Leyronas, research officier at AFD