Biodiversity loss and climate change are two of the biggest environmental crises of our time. They are inextricably connected, sharing some of the same drivers and therefore some of the same possible solutions. In this chapter, we consider socioscientific reasoning as critical thinking for responsible action in the context of biodiversity loss education. We focus on biodiversity loss as a global socio-ecological challenge that has been given less attention in public discourse. Biodiversity loss can be a cold, secret and specialised controversy for young people; cold because they do not perceive it as personally relevant, secret because they cannot easily visualise the changing environment, and specialised due to its complexity both as a scientific concept and as a socioscientific issue. To support students’ engagement with socioscientific reasoning as critical thinking for responsible action in the context of biodiversity loss education, we discuss two principles to consider in pedagogical approaches: (a) the need to make biodiversity loss an observable phenomenon for young people), and (b) framing biodiversity loss as a controversial, socioscientific issue). We conclude with a proposal for an educational sequence based on socioscientific inquiry-based learning that showcases how these principles can be implemented within primary school education.