New USAID Ecosystem-based Adaptation Evidence Summary and Case Study Series


Finding ways to adapt to the effects of climate change is no longer optional for most communities — it is necessary. The question is, what are the range of strategies for adaptation? Ecosystem-based adaptation (EbA) is a nature-based and people-centered approach that emphasizes ecosystem integrity as crucial for human resilience to climate change.

Biodiverse ecosystems like wetlands, forests and mangroves strengthen climate resilience by reducing the impact of floods and droughts, decreasing hillside erosion, and protecting lives and property against storm surge and high waves, among other adaptation benefits. Healthy ecosystems also provide a wide range of other benefits, from clean water for drinking to fertile soils for agriculture and habitat for fish, as well as a host of other services such as pollination, carbon sequestration and regulation of air quality. These ecosystem benefits support economic growth, food security and human well-being. EbA approaches can sustain the natural resource base that communities depend on and promote more stable, resilient and self-reliant societies. Conserving the ecosystems that provide these benefits is essential.

USAID has developed a series of evidence summaries and case studies highlighting the potential role of EbA in addressing climate vulnerabilities and contributing to development results. These can help decision-makers and development practitioners consider and identify where EbA is likely to be a relevant approach, either alone or as a component of a broader adaptation strategy.

The series include the following resources.

Evidence Summaries:

Case Studies:

Additional details on the resources are provided below.

Extreme Events

A number of EbA approaches can help communities become more resilient to extreme events. Restoration of upland forests can reduce landslides from strong storms, as well as protect against drought conditions by absorbing water and recharging groundwater supplies. Green spaces and roofs and vegetated riparian buffers in urban areas can mitigate extreme heat waves by decreasing daytime temperatures and contributing to cooler water temperatures. Restoring natural fire regimes to dry forests can reduce the impacts of uncontrolled wildfires. A case study from the Philippines illustrates the use of EbA to protect communities from extreme events.

Food Security

Climate stressors often magnify risks to food security, further threatening human health and economic productivity. Higher temperatures and lower levels of rainfall can decrease crop yields, shift planting windows, increase stress on livestock and change the prevalence of pest infestations. EbA activities that strengthen food security include planting shade trees to improve soil fertility and support pollinators, restoring and managing watersheds to maintain water supply for irrigation and intercropping to improve resistance to pest outbreaks. Other EbA approaches that support food security include protecting marine and freshwater habitats and strengthening fisheries management to ensure that fish stocks do not fall below minimum viability levels. Healthy ecosystems are also critical for the diversification of food sources, such as wild plants and indigenous crops. A case study from Bangladesh illustrates the use of EbA to strengthen food security.

Water Security

Climate change alters the timing, quantity, and quality of precipitation and water flows, leading to impacts on health, agriculture and infrastructure. EbA can be a cost-effective adaptation strategy to maintain and increase the quantity and quality of water and strengthen water security by recharging aquifers and improving natural water storage. EbA approaches such as the conservation or restoration of forests, wetlands and mangroves can reduce flood and drought risk, prevent soil erosion and provide physical buffers that retain excess water and dissipate wave energy. Agroforestry and conservation farming can reduce agricultural water demand and help increase farmers’ resilience during droughts. Case studies from Peru and Mongolia and illustrate the use of EbA to improve water security.

Coastal Populations

Climate stressors, such as sea level rise, increasing ocean temperatures and ocean acidification pose significant risks to the well-being and assets of coastal populations. A combination of sea level rise, strong storms and increased rainfall may also lead to the submergence of coastal areas. EbA approaches can often help coastal populations adapt to the adverse impacts of climate change. For example, restoration of mangroves, coral reefs and other natural systems can help attenuate coastal erosion and storm surge. Healthy coastal ecosystems can also act as barriers against extreme events, capture sediment and slow destructive wave energy. A case study from the Seychelles illustrates the use of EbA to protect coastal populations.

Economics of EbA

Importantly, EbA approaches can be cost-effective. A study examining the cost-effectiveness of EbA to address erosion and landslides in mountainous regions of Nepal and Peru found that EbA interventions—adoption of sustainable grassland management for grazing livestock and the cultivation of commercially valuable, deep-rooted native grasses that better stabilized slopes—were two times and nine times more cost-effective than business-as-usual scenarios in Peru and Nepal respectively. A cost-benefit analysis comparing mangrove restoration (an EbA approach) with construction of an earthen dike in Mozambique (a hard infrastructure approach) to protect a coastal city from frequent flooding found that mangrove restoration had positive financial and economic net present values (a measure that reflects return on investment) that exceeded the dike alternative, largely because restoration provided additional benefits such as carbon sequestration and fish production.