Tree Crops, a Permanent Agriculture: Concepts from the Past for a Sustainable Future

J. Russell Smith (1874–1966), a professor of geography at Columbia University, witnessed the devastation of soil erosion during his extensive travels. He first published his landmark text, Tree Crops, A Permanent Agriculture in 1929, in which he described the value of tree crops for producing food and animal feed on sloping, marginal, and rocky soils as a sustainable alternative to annual crop agriculture less suited to these lands. A cornerstone of his thesis was using wide germplasm collection and plant breeding to improve this largely underutilized and genetically unexploited group of plants to develop locally adapted, high-yielding cultivars for the many climatic zones of North America. Smith proposed an establishment of “Institutes of Mountain Agriculture” to undertake this work. For a variety of reasons, though, his ideas were not implemented to any great degree. However, our growing population’s increasing demands on natural resources and the associated environmental degradation necessitate that Smith’s ideas be revisited. In this review, his concepts, supported by modern scientific understanding and advances, are discussed and expanded upon to emphasize their largely overlooked potential to enhance world food and energy security and environmental sustainability. The discussion leads us to propose that his “institutes” be established worldwide and with an expanded scope of work.