Drawing on an ecological approach, we trace how the political-economy of drug wars are locally materialised in relation to health. We take the case of coca cultivation and eradication as our example. To make our analysis, we trace the different ways that the chemical glyphosate is materialised in a war with the coca plant in Colombia. Glyphosate has been used for decades in aerial fumigation campaigns to eradicate illicit coca cultivation. Our analysis traces the more-than-human effects of glyphosate in relation to health. This leads us to outline a more-than-human approach to harm reduction; a harm reduction which positions health as a matter of ecology, paying attention not only to the nonhuman actors affecting human health but also to the health of environments which are themselves always in-the-making. We envisage harm reduction as a collaboration in which humans 'become-with' their environments.