Community solidarity, adaptive capacity and collaboration: a realist review of how the third sector adapts and responds to crisis

The COVID-19 pandemic highlighted the critical role of the third sector and mutual aid in supporting vulnerable populations through crisis response. This study asks how community resilience (mobilising resources to cope with crises) is enabled by third sector and mutual aid responses in the United Kingdom. We conducted a realist review of UK peer-reviewed and grey literature using stakeholder-agreed search terms. Of 366 records identified, 55 contained sufficient explanatory detail to develop and test programme theories. Iterative analysis refined initial propositions into three overarching theories, represented through three Context–Mechanism–Outcome configurations. Findings emphasise the importance of community solidarity through shared adversity, adaptive capacity drawing on specialist knowledge, cross-sector collaboration and trust-based networks that enable rapid scaling. Collaborative roles were often temporary; without formal recognition and longer-term governance infrastructure, crisis response may remain fragile and fragmented. These theoretical models provide transferable explanations to inform crisis preparedness, adaptation planning, and resourcing of community-based responses.