Coastal lowlands are increasingly exposed to flood risks from sea-level rise and extreme weather events (1). Megacities like Shanghai, London, New York, and Bangkok that lie in vast river deltas are particularly vulnerable. Dramatic flood disasters include the Indian Ocean tsunami in 2004, Hurricane Katrina in New Orleans in 2005, Hurricane Sandy in New York in 2012, and Typhoon Haiyan in the Philippines in 2013.

Ecosystems are not merely vulnerable to climate change but, if sustainably restored and protected, are a major source of human resilience. Not only is the science evidence-base for this perspective growing rapidly, but ecosystems are featuring with increasing prominence in global climate change policy.

There is growing recognition that naturebased (or ‘green’) solutions - i.e. the restoration or rehabilitation and protection of natural habitats - when applied strategically and equitably can not only safeguard biodiversity and ecosystem services but also help people adapt to climate change [1,2]. The type of NbS targeted at helping people adapt to the impacts and hazards of climate change is widely referred to as “Ecosystem-based Adaptation” (EbA).

Changes in global climate are increasingly having adverse impacts on human populations and natural systems. This has resulted in increased efforts to come up with options that can mitigate the impacts, as well as help to adapt to already occurring changes.

This booklet sets out guidance for assessing the effectiveness of an ecosystem-based approach to climate change adaptation. It describes a process, based around asking a detailed set of questions, that can be used by project managers and researchers to shape project design, assess the progress of an ongoing project or draw conclusions about the effectiveness of a project that has ended.

The idea of ‘nature-based solutions’ (NBS) is now being used to reframe policy debates on biodiversity conservation, climate change adaptation and mitigation strategies, and the sustainable use of natural resources, among other issues. While interesting and potentially useful for those debates, it is a concept that still needs to be clearly defined; its use is not confined to discussions about ecosystem services and natural capital.

In this paper, we reflect on the implications for science, policy and practice of the recently introduced concept of Nature-Based Solutions (NBS), with a focus on the European context. First, we analyse NBS in relation to similar concepts, and reflect on its relationship to sustainability as an overarching framework. From this, we derive a set of questions to be addressed and propose a general framework for how these might be addressed in NBS projects by funders, researchers, policy-makers and practitioners. We conclude that:

Many national and international environmental agreements acknowledge that the impoverishment of ecosystems is limiting the world’s capacity to adapt to climate change and that ecosystem-based adaptation (EbA) approaches should be harnessed as a priority. EbA has the potential to increase adaptive capacity and social and ecological resilience to climate change in both developed and developing countries.

Many of the world’s vital natural ecosystems, and the communities reliant on them, are vulnerable to climate change. But there is increasing recognition that ecosystems — if sustainably restored and protected — can also form a strong line of defence against the direct impacts of climate change and support human adaptation over the long term. As the evidence base grows, ecosystems are increasingly prominent in climate change policy, especially in developing nations. Yet intentions rarely translate into robust and informed measurable targets, undermining action.