Chapter 3 situates these empirical flows and the concepts we need to understand them within the larger historical process of imperialism, going back to the colonial period through which the world was integrated into Western-dominated trade and investment patterns. The history of imperialism and capitalism are clearly intertwined, but early environmental debates were also intertwined, as colonial managers were amongst the first to start to address environmental degradation, notably deforestation, from the late eighteenth century onwards. Environmental debates have since been left with a legacy of their inter-relation with varied forms of inequalities and exploitative relations. The chapter introduces the concept of ‘ecologically unequal exchange’ to capture these relations, and explores the contemporary legacy of this in North–South environmental political debates, for example over toxic waste, food flows, biotechnology and biodiversity, and most recently carbon debt and colonialism.