The Carmen-Pajonal-Machona lagoon system (CPM) is located along Mexico Gulf in the State of Tabasco. It is a low-depth coastal wetland which is separated from the ocean by a fragile sand bar. It communicates with the sea through two inlets and hosts important habitats (including mangroves) and medium-small human communities, strongly relying on the lagoon ecosystem services for their subsistence.

The Consortium formed by Thetis, CMCC and Coastal Environments run a project funded by the World Bank and technically managed by the Instituto Nacional de Ecología y Cambio Climático, aiming to design adaptation measures to climate change and other human-induced impacts.

The project was developed through different steps: (i) data collection and field activities, (ii) analysis of the current vulnerability of the lagoon system, (iii) elaboration of climate change scenarios at the regional level, (iv) assessment of climate change impacts, (v) identification of adaptation measures and possible sites for their implementation, (vi) recommendations for institutional strengthening. Stakeholder engagement was consider essential for the whole project and two interactive workshops were organised: one focusing on the assessment of current and climate change related impacts and a second on the validation of adaptation measures proposals. Both workshops involved local decision makers and experts (day 1) and representatives of local communities (day 2).

The current state of and main impacts on CPM were identified in the initial phase of the project also based on the EEA DPSIR conceptual approach. Main outcome highlighted: erosion of the littoral bar separating the lagoon from the ocean, high social and physical vulnerability to flooding of neighbouring areas, lack of treatment of wastewater and bacteria contamination of the lagoon, loss of mangrove habitats, saltwater intrusion and salinization of soil, local soil contamination due to oil extraction, consequent impacts on agriculture and fishery, and high vulnerability of local communities.

Based on the elaboration of regional climate change, sea-level rise and subsidence projections (accordingly to RCP4.5 and RCP8.5 scenarios and considering 2030 and 2100 timeframes), the project analysed how climate change can exacerbate those impacts (e.g. increased erosion or break of the littoral bar, increased frequency and intensity of flooding events, expansion of areas affected by soil salinization) and induce other effects (e.g. mangrove inland migration).

Afterwards, the project identified most vulnerable areas and adaptation measures that might be realised to improve the system resilience. A number of criteria were considered for the selection of those measures, including: technical feasibility, replicability, possible adoption of ecosystem based solutions, coherence with existing programs and plans, and in particular relevance for local communities and the possibility to rely on their capacity for the construction and management of the measures.