In the middle of Panama’s massive Gatun Lake lies Barro Colorado Island, a rainforest preserve and research center owned by the Smithsonian Institution. But the island isn’t natural, and the reservoir it sits on is the main passage of the Panama Canal.

Every time a ship passes through the Panama Canal, Gatun Lake flushes 52 million gallons of fresh water through locks and into the ocean. The only source of that water is runoff from the rainforests, which means the well-being of the rainforest directly correlates with the ability for the Canal to pass ships, which, in turn, keeps all of Panama’s economy, and much of the world’s economy afloat.

We talk with Ashley Carse of Vanderbilt University about how infrastructure like the Panama Canal has wide-reaching social and political implications