As regulative institutions, Andean barter markets help sustain local food systems and the ecosystems in which they are embedded. Action research with indigenous communities in the Lares Valley (Department of Cusco, Peru) generated new evidence on the importance of barter markets for: - giving some of the poorest social groups in the Andes better food security and nutrition; - conserving agricultural biodiversity (genetic, species, ecosystem) through the growing and exchange of native food crops in barter markets; - maintaining ecosystem services and landscape features in different agro-ecological zones; and - enabling local, autonomous control of production and consumption – and more specifically control by women over key decisions that affect both local livelihoods and ecological processes. The resilience of linked social and ecological systems is enhanced as a result of this dynamic management of biodiversity and economics by Andean indigenous peoples.