Several influential river histories published in the past several decades have used systems-theoretic ideas and language to break down boundaries between nature and culture, between environment and technology, and between the humanities and the natural sciences. These works have served as models not only for historical research on rivers but for research on landscapes and environments in general. At the same time, a number of recent river histories have eschewed talk of systems, instead approaching rivers as historical agents and geographical places. Through a selective survey of recent works in the history of science and environmental history, this chapter offers a critical assessment of the use of systems theory and systems language to understand the entangled natural-cultural histories of landscape features and the Earth as a whole.