The researchers analyzed downstream ecosystems from four rivers, two dammed and two unobstructed, in the Mexican Pacific states of Sinaloa and Nayarit. They found dramatic coastal recession along the mouths of the obstructed rivers, including in vital ecosystems like mangrove forests, which provide protection from storms, commercial fishery habitats, and belowground carbon storage. The rivers that the researchers studied run roughly parallel to each other through similarly-developed land, into large coastal lagoon systems. The Santiago and Fuerte rivers have dams that provide hydroelectric power for the region, but withhold 95% of the flow of these rivers. Meanwhile, the San Pedro and Acaponeta rivers are relatively free-flowing and undammed, with over 75% of the rivers remaining unobstructed.