Food systems must provide sufficient, adequate and accessible food for all, in a sustainable way. This is a major challenge:

• Food systems are increasingly exposed to drivers of change, ranging from sudden shocks to long-term stressors, such as natural disasters, pest outbreaks, economic and political crises, climate change, resource degradation, etc. Many of these drivers of change are hard to predict, and therefore hard to manage. 
• Food systems are intrinsically complex: they comprise of many different processes, value chains, actors and interactions; their outcomes affect multiple stakeholders and sectors in diverse and sometimes conflicting ways. Thus, food systems themselves, and their outcomes, are also hard to predict and to manage.

Food systems resilience is defined as "the capacity over time of a food system and its units at multiple levels, to provide sufficient, adequate and accessible food to all, in the face of various and even unforeseen disturbances" (Tendall, et al. 2015, p. 19). It is complementary and essential to sustainability.