SEICAT+: a conceptual assessment framework for positive socio-economic impacts of alien species on human well-being

Despite their well-documented negative impacts on human well-being and biodiversity, alien species outside domestication or cultivation can also generate socio-economic benefits. Recognizing these benefits is important for identifying stakeholder conflicts and for informed decision-making by managers and policymakers. Such benefits may arise from enhancements of ecosystem services—such as the provision of food, timber, and other natural resources—or from reductions of ecosystem disservices, for example through the control of agricultural or medical pests. Although these positive impacts are broadly acknowledged, no unified framework yet exists to classify them in a way that enables systematic and rigorous comparisons across species and contexts. A key challenge is the absence of a common metric for evaluating the magnitude of diverse socio-economic benefits of alien species. Monetary assessments can capture some benefits—such as revenue from timber extraction or avoided damage due to biocontrol programs—but they struggle to account for non-market values, including natural resources (e.g. clean air), cultural contributions and health-related outcomes. Frameworks based on Ecosystem Services (ES) or Nature’s Contributions to People (NCP) offer broader perspectives but often rely on context-specific or non-comparable metrics. We argue that conceptualizing the human benefits of alien species through the lens of the capability approach—evaluating changes in people’s preferred activities and states of being as proxies for well-being—provides a holistic framework and a practical, relevant, and comparable metric for socio-economic impact assessment. We introduce SEICAT+ (the positive Socio-Economic Impact Classification for Alien Taxa), a framework designed to capture beneficial impacts of varying magnitude across all constituents of human well-being: basic materials for a good life, security, health, good social relations, and freedom of choice and action. We show how SEICAT+ can complement existing approaches based on monetary valuation, ES, and NCP, and how it can integrate with other similarly structured alien-species impact assessment frameworks—thus improving their scope, comparability, and robustness.