A systematic global stocktake of evidence on human adaptation to climate changeAssessing global progress on human adaptation to climate change is an urgent priority. Although the literature on adaptation to climate change is rapidly expanding, little is known about the actual extent of implementation. We systematically screened >48,000 articles using machine learning methods and a global network of 126 researchers. Our synthesis of the resulting 1,682 articles presents a systematic and comprehensive global stocktake of implemented human adaptation to climate change. Documented adaptations were largely fragmented, local and incremental, with limited evidence of transformational adaptation and negligible evidence of risk reduction outcomes. We identify eight priorities for global adaptation research: assess the effectiveness of adaptation responses, enhance the understanding of limits to adaptation, enable individuals and civil society to adapt, include missing places, scholars and scholarship, understand private sector responses, improve methods for synthesizing different forms of evidence, assess the adaptation at different temperature thresholds, and improve the inclusion of timescale and the dynamics of responses.

We present the first systematic, global stocktake of the academic literature on human adaptation. We screen 48,316 documents and identify 1,682 articles that present empirical research documenting human efforts to reduce risk from climate change and associated hazards. Coding and synthesizing this literature highlights that the overall extent of adaptation across global regions and sectors is low. Adaptations are largely local and incremental rather than transformative. Behavioural adjustments by individuals and households are more prevalent than any other type of response, largely motivated by drought and precipitation variability. Local governments and civil society are engaging in risk reduction across all sectors and regions, particularly in response to flooding. Urban technological and infrastructural adaptations to flood risk are prevalent in Europe, while shifts in farming practices dominate reporting from Africa and Asia. Despite increasing evidence of adaptation responses, evidence that these responses are reducing risks (observed and projected) remains limited.

Voluntary property buyouts have been the most prevalent form of managed retreat in the USA to date. Tens of thousands of households have sold their flood-prone homes to the government, and after the structures are demolished, the land becomes open space. Concerns have been raised about the equity of buyout processes and outcomes, spanning distributive, procedural, and interactional dimensions of social justice. In this policy analysis, we first provide an overview of equity and justice issues in buyouts based on existing literature. We consider multiple relevant stakeholder groups: the communities in which buyouts occur, potential participants and relocating households, residents who choose to stay, and the destination communities. Second, we present policy options that may address and reduce existing social inequities in buyouts. Third, we outline how improved reporting on buyout programs by implementers can support buyout policy learning that will improve buyout outcomes and equity. Indicators can provide insight on who has access to buyouts, the effect of buyout implementation on outcomes, and the consequences of relocating—or not—for all affected. With increasing climate risks, voluntary property buyouts will remain an important means of reducing exposure to flooding and other hazards. For this method of retreat to occur effectively at greater scale, attention to social justice in program evaluation and policy learning is necessary.

Societies throughout the world are experiencing more severe and frequent flooding with consequences for people’s livelihoods, health, safety, and heritage. Much flood risk management to date has aimed to maximize economic benefits, reduce the likelihood of flood disasters, and facilitate recovery where needed. It has assumed a stationary climate and focused on extremes and financial losses. But this paradigm of flood control is increasingly at odds with the full set of challenges and requirements for flood risk management. Critical challenges motivate a shift from flood control to flood adaptation. First, under climate change, flood risks are intensifying and changing, and new normals are appearing, such as daily high-tide flooding or permanent inundation. Fully controlling flood hazards with one-time interventions is increasingly untenable. Second, floods affect numerous, multidimensional aspects of human and ecological well-being and social justice. Past flood control efforts, and the decision-making processes that produced them, have often failed to address these multidimensional concerns or even had negative side effects. Fundamental adjustments are emerging and will be needed: a guiding paradigm of flexibility rather than control, a system-wide approach with coordinated action across scales, and increased attention to the full range of priorities relevant to successful interventions. For example, science and research for flood risk adaptation increasingly involve processes supporting usable, inclusive knowledge tailored to decision contexts. Integrative science partnerships such as collaborative flood modeling can incorporate the dynamic physical and social landscapes of flood drivers, impacts, and management. Flexible processes allow updating as flood risks change, and collaborative processes can build intuition, trust, and understanding of risks, including improved awareness of the values and relationships that are threatened and preferred response options. The goal of flood risk management is no longer limited to preventing floods; flood risk management must balance risk tolerances with ecological and social benefits and weigh the trade-offs of management strategies against other societal goals. This “science for society” is inherently political, requiring careful attention to and evaluation of who participates, whose goals are prioritized, and who benefits. Furthermore, methods of evidence-based decision-making must be able to accommodate deep uncertainties, changing risks and values, and limits to responses. Shifts are already occurring, including dynamic adaptive management practices and improvements to tools such as cost–benefit comparisons. These changes illustrate a larger reframing within flood risk management, away from disaster management focused on extreme isolated events and toward adaptation in response to enduring changes across both extreme and average conditions. The current challenges of flood risk management create opportunities for integrating lessons from diverse domains of actionable science and public policy and thereby innovating processes of climate adaptation relevant to a range of climate risks.