The ecosystem service framework has been instrumental in navigating local to global sustainability issues. Yet as ecosystem services (ES) focus on nature's positive contributions to people, some have argued that 'ecosystem disservices' (EDS), or nature's negative contributions, should also be taken into account to better orient sustainability policies. However, joint ES and EDS assessments remain rare in sustainability research, partly because of the persisting conceptual ambiguity around the EDS concept. This study aimed to develop these joint assessments and test their relevance in addressing sustainability issues. To this end, we devised a novel cascade model that helps to define ES and EDS in a multi-level context that considers both as coproduced by ecosystems and people. In order to explore the potential and limitations of this model, we then applied it in a Brazilian landscape where reconciling agriculture and forest conservation is a critical sustainability challenge. Using the model in comprehensive interviews with farmers about their perceptions and management practices of forests, we found that they had an overall positive valuation of forests, but identified both positive and negative interactions between forests and farms at different organizational levels. The model also revealed a vicious circle between crop expansion, a resulting decrease in certain ES and an increase in certain EDS, which might exacerbate tensions between agriculture and forest conservation in the future. Additionally, the model allowed a window on the diverse preventive and regulating practices that the interviewed farmers have adopted to cope with increasing EDS without necessarily harming biodiversity. Based on this case study, this novel cascade model seems a promising conceptual tool to uncover the interactions between ES and EDS, opening new research and policy avenues to support sustainability.