Channel changes and living fencerows in eastern sonora, mexico: myopia in traditional resource management?

Abstract

ABSTRACT The riverine landscape of the eastern half of the state of Sonora, northwest Mexico, is characterized by cultural features that may well be unique to the region. Living fencerows are constructed by fanners planting willow and cottonwood saplings well out into river channels during the dry season, when discharge is low and restricted to rivulets in the middle of the otherwise dry streambeds. They are arranged more or less parallel to the channels and the edges of adjacent fields, and eventually sprout and establish roots. Brush is woven between the saplings, to stabilize them, and to slow stream flow along the channel edges during the rainy season when discharge is at its annual peak. Diminished velocities behind the fencerows result in decreased stream bank erosion, and increased sedimentation, at least in theory. On the whole, living fencerows are envisaged by the farmers who construct them, and by environmentalists, as ecologically sound strategies to protect, fertilize, and enlarge fields. As advantageous as they may seem, however, there is at least one negative consequence of living fencerows. This paper suggests that by narrowing and straightening stream channels, living fencerows contribute to increased stream velocity, and hence, increased stream bank erosion and field destruction, especially downstream from these features. Advantages that accrue to the builders of living fencerows come at the expense of their neighbors. The assumptions of farmers having total knowledge of their environments, and total understanding of their actions are questioned.