Agroforestry: The North American Perspective

by

Sarah T. Lovell, Harold E. "Gene" Garrett

• LAST REVIEWED: 12 January 2021
• LAST MODIFIED: 12 January 2021
• DOI: 10.1093/obo/9780199363445-0130

Introduction

Agroforestry has a long, rich history that is rooted in activities practiced by indigenous communities around the world. Native peoples were known to gather fruits, nuts, and understory herbs from the forest, based on their deep ecological knowledge of the natural system, and they often cultivated preferred species. For modern applications, agroforestry can be defined as the intentional integration of trees and shrubs with crops or livestock to create a multifunctional system with a wide range of benefits. In temperate regions, agroforestry is characterized by six key practices: (1) alley cropping—planting rows of trees with a companion crop grown between the rows; (2) forest farming—growing high-value specialty crops in the shaded forest understory; (3) riparian buffers—protecting water resources such as streams with a zone of trees, shrubs, and herbaceous plants; (4) silvopasture—combining trees, forage, and livestock for multiple products; (5) windbreaks—planting rows of trees and shrubs to protect crops or livestock from wind and to reduce soil erosion; and (6) urban food forests—integrating trees, shrubs, and herbaceous plants that provide edible products for the good of the community. The environmental benefits of agroforestry have been widely studied and continue to be a source of great interest. Most recently, the potential for agroforestry to contribute to climate change adaption and mitigation is being explored. While the science of agroforestry has been influenced to a great extent by the field of ecology and related disciplines, social science dimensions are increasingly captured through the study of adoption behaviors, preferences, and cultural benefits. The investigation of the role of economic and policy drivers is critical to understanding strategies to motivate landowners to adopt these practices at a level that would expand agroforestry into the mainstream. Landscape-level planning and design could provide a vision and a pathway for a broader transformation to a system that encourages perennial habitats including specialty crops that supply edible products. Such a strategy could place agroforestry more directly into the growing call to support regional food systems and positive human health outcomes. This article focuses on the trends and directions in agroforestry research primarily in North America, with emphasis on developments in the early 21st century.

Agroforestry Foundations

Ecological principles underlying agroforestry have focused on species interactions in Batish, et al. 2008; Jose, et al. 2004; Ong, et al. 2015; and Nair 1993. Many sources such as Garrett 2009 classify and organize agroforestry into five practices that include alley cropping, forest farming, riparian and upland buffers, silvopasture, and windbreaks. Jose, et al. 2018 emphasizes ecosystem services provided by agroforestry. The volume Gordon, et al. 2018 explores regional context, applications, and opportunities. The application of landscape ecology principles to agroforestry is often understudied in the sources that seek to cover the ecological foundations of agroforestry. The historic book Smith 1929 and several recent publications begin to address this gap, such as Lovell, et al. 2018 and Molnar, et al. 2013.

• Batish, D. R., R. K. Kohli, S. Jose, and H. P. Singh. 2008. Ecological basis of agroforestry. Boca Raton, FL: CRC.

  This comprehensive book explores the ecological principles underlying the performance of agroforestry systems, with emphasis on the interaction between plant species, as well as environmental influences on the system.

• Garrett, H. E., ed. 2009. North American agroforestry: An integrated science and practice. 2d ed. Madison, WI: American Society of Agronomy.

  Known as the standard textbook for temperate agroforestry. Written for applied scientists, the chapters cover each of the agroforestry practices as well as socioeconomic factors and landscape perspectives. The full volume serves as the foundation of college-level introductory courses on agroforestry.

• Gordon, A. M., S. M. Newman, and B. R. W. Coleman. 2018. Temperate agroforestry systems. 2d ed. Wallingford, UK, and Boston: Centre for Agriculture and Bioscience International.

  Comprehensively covers agroforestry applications in temperate regions including Canada, United States, China, New Zealand, and Patagonia region of Argentina. For each region, authors typically describe the historical context, current applications and practices, and opportunities and barriers to greater adoption.

• Jose, S., A. R. Gillespie, and S. G. Pallardy. 2004. Interspecific interactions in temperate agroforestry. Agroforestry Systems 61–62:237–255.

  Primarily focused on North America, the article reviews the literature on ecological principles underlying interactions between different tree, shrub, or crop species. Above- and below-ground interactions are discussed.

• Jose, S., M. A. Gold, and H. E. Garrett. 2018. Temperate agroforestry in the United States: Current trends and future directions. In Temperate agroforestry systems. 2d ed. Edited by A. Gordon, S. M. Newman, and B. Coleman, 50–72. Wallingford, UK, and Boston: Centre for Agriculture and Bioscience International.

  Covers the five agroforestry practices most common in the United States: alley cropping, silvopasture, riparian and upland buffers, windbreaks, and forest farming. New opportunities for agroforestry are discussed, with the most currently relevant topics including applications with high-value organic and/or specialty crops, or the potential integration into an urban setting as with food forests.

• Lovell, S. T., C. Dupraz, M. Gold, et al. 2018. Temperate agroforestry research—considering multifunctional woody polycultures and the design of long-term field trials. Agroforestry Systems 92:1397–1415.

  Explores the production capacity of trees and shrubs in an agroforestry system, including valuable products such as fruits, nuts, and timber products. The need for long-term experiments is emphasized, drawing from case studies at Restincliéres Estate Farm in France and University of Missouri Center for Agroforestry.

• Molnar, T. P., P. Kahn, T. Ford, C. Funk, and C. Funk. 2013. Tree crops, a permanent agriculture: Concepts from the past for a sustainable future. Resources 2:457–488.

  Revisits J. Russell Smith’s 1929 book, Tree Crops: A Permanent Agriculture (see Smith 1929), to consider the contemporary value of placing greater emphasis on tree crops through collecting germplasm, breeding woody plants for production, and establishing long-term research trials. Recommendations for certification procedures to enforce best management practices are discussed.

• Nair, P. K. R. 1993. An introduction to agroforestry. Berlin: Springer.

  Developed as a textbook for graduate-level agroforestry courses, this book was one of the first to support educational efforts worldwide. While the emphasis is primarily on tropical areas, many of the concepts can be applied in temperate regions. Basic principles on species interactions, soil health, and system design are covered in depth.

• Ong, C. K., C. R. Black, and J. Wilson, eds. 2015. Tree-crop interactions: Agroforestry in changing climate. 2d ed. Wallingford, UK, and Boston: Centre for Agriculture and Bioscience International.

  Specifically focuses on the relationship between tree and crop species in these unique mixed-cropping systems, so the applications are most relevant for alley cropping and other multi-strata systems. The second edition emphasizes the value of agroforestry for climate change adaptation.

• Smith, J. R. 1929. Tree crops: A permanent agriculture. Rahway, NJ: Quinn & Boden.

  This pivotal book has inspired many contemporary agroforestry experts because of the visionary proposal to focus resources on the development of woody crops for the production of nuts, fruits, and other products. The concept of “Institutes of Mountain Agriculture” establishes a path for the use of the agricultural experimental stations in the United States to study tree crops, which, if undertaken at the time, could have changed the trajectory of our food system.