Maintenance of human well-being is highly dependent on nature. The natural environment provides a source of both directly used goods and services that support human livelihoods and an intrinsic value that contributes to human flourishing. Today, much of the planet is influenced or even transformed by human activity, and natural ecosystems are increasingly under threat. Ecology and conservation biology are crucial for understanding and quantifying changes in ecological systems. Moreover, ecology in conjunction with other branches of science provides key insights to enable management options for supporting a sustainable future for our planet. Here, we give an overview of the relationship between biodiversity, ecosystems, and sustainability. First, we introduce the notion of biodiversity, then we present the links between biodiversity, ecosystem functions, and services, in which ecosystem services are the benefits people derive from ecosystems. Finally, we outline the current threats to ecological integrity and provide a brief overview of the links between ecology and other disciplines within sustainability science.