UBC Theses and Dissertations

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UBC Theses and Dissertations

Perennial agriculture : agronomy and environment in long-lived food systems Kreitzman, Maayan


Perennial agricultural systems are fundamentally characterized by their longevity, as they consist chiefly of long-lived woody plants with permanent root and shoot systems that can be managed for continuous ground cover. This is known to promote a host of ecosystem services, and indeed agricultural landscapes that include perennials have been shown to support wildlife, enhance pest regulation, sequester carbon, limit erosion and water pollution, and promote pollination. Yet, the agroforestry and agroecology literatures that characterize environmental benefits of perennials (which mostly involve non-food producing trees and grasslands, especially in temperate climates) are largely separate from agronomic literature about the management and yields of perennial crops themselves. Thus little is known about how tree crops actually support a range of ecosystem services and other benefits. This thesis takes a multi-disciplinary approach to study agronomic, nutritional, environmental, and social dimensions of perennial crops for human food. It first characterizes the distribution and yields of perennial staple crops worldwide, finding that perennial crops, many of which are not yet heavily commodified, can provide staple nutrition at yields comparable to those of annual staples while supplying more varied nutrition than common annual staples. Second, it surveys food production and environmental outcomes on fourteen perennial polyculture farms in the US Midwest, finding that these farms enhance biodiversity and several other ecosystem services, although these new plantings produce less food than neighboring annual cropland. Third, it explores the practices, livelihoods, and values of perennial farmers, finding that they implement sophisticated adaptive management and derive satisfaction from fulfilling largely relational values alongside livelihood needs. Perennial agriculture thus offers the potential to produce significant amounts of nutritionally important food in multifunctional landscapes. If managed in diversified systems, perennials can enhance multiple ecosystem services compared to simplified perennial management and annual cropland. More widespread transition to perennials in existing agricultural land should be informed by the specific ecological opportunities offered by perennial plants (including continuous groundcover), and by the knowledges and values of producers, to realize the potential of these systems for achieving sustainable food security.

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