SEICAT+: a comprehensive assessment framework for positive socio-economic impacts of alien species

Despite their recognized harms to humans and biodiversity, alien species outside of domestication/cultivation can also provide socio-economic benefits, which are essential to consider when identifying stakeholder conflicts and informing managers and policymakers. These benefits often result from the enhancement of ecosystem services, such as the provision of food, timber, and other natural resources, or from the reduction of ecosystem disservices, such as the control of medical or agricultural pests. While such positive impacts are generally acknowledged, there is still no unified framework to classify them in a way that allows systematic and rigorous comparisons across species and contexts. A major obstacle is the lack of a common metric for evaluating the diverse socio-economic impacts of alien species. Monetary approaches can capture some benefits —such as income from logging or biocontrol programs—but fall short in their ability to assess non-market values, such as cultural benefits or health outcomes. Ecosystem Services (ES) and Nature’s Contributions to People (NCP) provide broader perspectives but often rely on non-comparable or context-specific metrics. We argue that framing the benefits of alien species for humans through the lens of the capability approach—and assessing changes in people’s preferred activities and states of being as proxies for well-being—offers a holistic concept and relevant and comparable metric for socio-economic impact assessments. We introduce SEICAT+ (the positive Socio-Economic Impact Classification for Alien Taxa), a framework designed to capture impacts of varying magnitudes across all constituents of human well-being, i.e. basic materials for a good life, security, health, good social relations and freedom of choice and action. We demonstrate how SEICAT+ can complement existing approaches based on monetary quantification, ES and NCP, and how it can integrate with other, similarly-structured, impact assessment frameworks for alien species—thereby enhancing the scope and robustness of their socio-economic evaluations.