"Throughout human history, people have settled disproportionately along rivers, relying on the rivers for , , fertile agricultural soils, , and food from aquatic and riparian organisms. People have also devoted a tremendous amount of time and energy to altering river processes and form. We are not unique in this respect: ecologists refer to various organisms, from to some species of , as s in recognition of the ability of these organisms to alter the surrounding environment. People are unique in the extent to and intensity with which we alter rivers. In many cases, river engineerings has unintended consequences, and effectively mitigating these consequences requires that we understand rivers in the broadest sense, as shapers and integrators of . once described rivers as the gutters down which flow the ruins of continents (Leopold et al., 1964). His father, Aldo Leopold, described the functioning of an ecosystem as a round river to emphasize the cycling of s and energy."