Feasibility of nature-based adaptation in deltas
Nature-based adaptation is widely touted as a promising solution to deal with future environmental change. But what is the feasibility in coastal deltas? This project of the Water, Climate & Future Deltas hub assesses the feasibility of nature-based adaptation in the contrasting Rhine and Mekong deltas.
Nature-based adaptation involves working with, rather than against or independent of, natural ecosystem structure and processes while adapting to environmental change such as sea level rise. Gaining in popularity globally, nature-based adaptation is seen as a ‘win-win’ solution, in which human development can be maintained while also enhancing ecosystems in a particular place. Yet, it remains to be seen how successful nature-based adaptation will be at large scales.
This Water, Climate & Future Deltas hub project, led by MSc graduate Mandy Paauw and researcher Dr. Murray Scown, assesses the feasibility of nature-based adaptation in the contrasting Rhine and Mekong deltas. Nine nature-based adaptation options for deltas are catalogued from a comprehensive review of scientific and policy literature (listed below). The nine options are then evaluated based on their environmental (e.g., sufficient sediment, slow rates of sea level rise) and policy (e.g., financial support, stakeholder engagement) requirements.
- Coastal wetland restoration (e.g., mangroves)
- Riverine wetland restoration
- Reforestation of riparian zones
- Restoration of dynamic dune systems
- (Re)construction of biogenic reefs (e.g., oyster and mussel beds)
- Restoring seagrass beds
- Ecological enhancement of dikes
- Restoring natural sedimentation processes
- Beach nourishment
Nature-based adaptation is not a ‘silver bullet’ for deltas
The results of the project show that all but two nature-based adaptation options are constrained by environmental limitations in the Rhine and Mekong deltas. Construction of biogenic reefs and ecological enhancement of dikes are the two most feasible options in these deltas, based on environmental limitations. Others are constrained by existing land use, insufficient sediment supply, and expected high relative sea level rise.
Policy, on the other hand, is quite supportive of nature-based adaptation in these two deltas, based on their delta plans. Tangible support, well-defined boundaries, and participatory decision making are, in theory, the strengths of the two delta plans for nature-based adaptation.
Most of the nine nature-based adaptation strategies identified in existing publications are constrained by environmental factors in the Rhine and Mekong Deltas. Striped boxed indicate potential constraints. Construction of biogenic reefs and ecological enhancement of dikes are the two most feasible options in these deltas, based on environmental limitations. Further research is needed to quantify potential constraints of land use on nature-based adaptation. Figure: Paauw (2020).
The findings suggest hybrid solutions combining nature-based adaptation and ‘hard’ adaptation options (e.g., dikes) will be required in these deltas. Strong mitigation action to reduce global greenhouse gas emissions and control degradation in the deltas themselves (e.g., land subsidence) are also required to reduce the pressure for adaptation. Additional, hybrid forms of governance for delta adaptation should be adopted, including adaptive, transformative, and interactive (participatory) governance.
The full results of the research can be read in Mandy Paauw’s MSc thesis and in a forthcoming paper to be presented at the 2021 Bratislava Conference on Earth System Governance.