Europe) has made huge strides to refine relevant concepts and methodologies that fit the temperate zone and the Western, industrialized realities in which we live. As such, domestic agroforestry has evolved at the intersection of the well‐established fields of agriculture, horticulture, and forestry. As an emergent applied science, agroforestry has aligned with agroecology and established a research–education–development infrastructure that integrates across these well‐established but separate disciplines.
Inherent Constraints Being Overcome
Because domestic agroforestry has evolved within a modern society primarily located in a temperate region of the world, it has faced inherent constraints not found in most developing countries. First, the climate in much of North America is not conducive to fast plant growth, especially by long‐lived woody perennials. In addition, some of our indigenous tree species are naturally slow growing and yield only one primary product—usually timber. As a consequence, the use of trees for timber in many types of agroforestry practices do not directly yield useful or marketable products for many years—often after the life of the persons who planted them! Knowing this, domestic agroforestry has instead focused on overstory nut‐ and fruit‐bearing trees and shrubs that come into economic production in 3‐15 yr (e.g., elderberry [Sambucus nigra L. ssp. canadensis (L.) R. Bolli], aronia [Aronia sp.], eastern black walnut [Juglans nigra L.], pecan [Carya illinoinensis (Wangenh.) K. Koch], Chinese chestnut [Castanea mollissima Blume]). Furthermore, fast‐growing species of the genus Populus (hybrid poplar, cottonwood, etc.) and Salix (clonal willow) (Robertson et al., 2017; Volk et al., 2006) are being used for biomass (MacPherson, 1995) and as woody florals (Gold, Godsey, & Josiah, 2004) and are integrated into riparian forest and upland buffer production systems to provide multiple products and environmental services. Finally, native perennial grasses (e.g., switchgrass [Panicum virgatum L.]) are also being used for biomass and other ecosystem services within a variety of agroforestry practices (Gamble, Johnson, Current, Wyse, & Sheaffer, 2016; Schulte et al., 2017)
The United States is a modern, industrialized nation with an increasingly large educated, urban population. Therefore, agroforestry practices are being developed to simultaneously address the market opportunities in urban areas while also meeting specific interests, needs, and problems of rural landowners. Currently, obstacles to agroforestry adoption exist but are in the process of being overcome (de Jalon et al., 2018; Wilson & Lovell, 2016). Barriers include the expense of establishment, landowners’ lack of experience with trees (Faulkner et al., 2014), the time and knowledge required for management and marketing (Valdivia, Barbieri, & Gold, 2012), and a lack of understanding by extension and state and federal agency professionals.
Agroforestry practices also have to compete with commodity crops, which have well‐developed government support systems providing insurance and price guarantees that significantly reduce landowner risk. Agroforestry practices do not, at present, have the same level of support, requiring that the landowner take on significant risk in adopting agroforestry practices. That said, the support structure and knowledge network for agroforestry is growing rapidly, addressing many of the issues constraining agroforestry adoption (Schoeneberger et al., 2017).
Evolving Infrastructure
The depth and breadth of the agroforestry research–education–application infrastructure has come a long way in the past 40 yr, developing most rapidly in the past decade. Coupled with an acceleration of biophysical and socioeconomic research, there are now positive changes in federal policy and positive market trends. The USDA–NRCS formally recognized temperate agroforestry practices in their cost‐share Environmental Quality Incentives Program (EQIP), helping promote agroforestry through national policy. Further support for growth of the agroforestry sector comes from positive consumer and market trends: increased demand for and promoting of “buy local”; growth of direct‐to‐consumer farmers markets; continued growth in the organic sector; and strong interest in pasture‐based livestock production.
Formally accredited online graduate certificate and master’s degree programs have been established; numerous extended‐duration training programs have been created and designed to train educators and landowners; NGOs (e.g., the Savanna Institute) and private sector (e.g., Iroquois Valley Farmland REIT, PBC Farms Beef) engage with landowners in agroforestry; multiple specialty crop and livestock cooperatives (e.g., elderberry, chestnut, hazelnut [Corylus spp.], aronia) have been formed; and robust financial decision support tools have been developed.
As it matures, this infrastructure must provide an interconnected feedback–feedforward knowledge system of researchers, teachers, extension personnel, and field practitioners to promote and support the development, refinement, and implementation of new ideas and practices (Gold, 2007).
Agroforestry as an Applied Science
The ongoing challenge is the continued development of domestic agroforestry practices along with the development of more discipline‐based land use strategies of sustainable agriculture and forestry. Almost 30 yr ago, Lassoie and Buck (1991) called for a major national commitment similar to the one mounted near the turn of the 20th century for agricultural production and forest conservation. As we begin 2021, large‐scale refocusing of the nation’s resources and professional energies has yet to fully materialize owing to the strength and ingrained structure of our current institutions and steady stream of state budget tightening. Nonetheless, concerns about the environmental impacts of current land use practices and the deterioration of the land base and water are increasingly being recognized as important problems to address (e.g., hypoxia, soil health). In spite of institutional and fiscal limitations, steady development efforts are underway to move domestic agroforestry from concepts to practices. During the past decade, steady progress has been underway at many different levels toward building a research–education–practice infrastructure involving a unique partnership including academia, state and federal governments, NGOs, the private sector, and agroforestry practitioners.
Research and Development
Since the second North American Agroforestry Conference (NAAC) (Garrett, 1991), there has been a dramatic increase in the amount of biophysical and socioeconomic agroforestry research in the United States and Canada. This is directly reflected in the chapters within this third edition of North American Agroforestry along with other recently published works and edited volumes (Gordon et al., 2018; Mosquera‐Losada & Prabhu, 2019; Schoeneberger et al., 2017). The 16th NAAC was held in 2019 and showcased a substantial amount of interdisciplinary research focused on specific opportunities where agroforestry practices can be applied. Temperate agroforestry research is regularly being reported at workshops and special sessions sponsored by professional societies, e.g., see recent abstracts of sessions at the American Society of Agronomy, Ecological Society of America, Society of American Foresters, and government agencies (e.g., USDA, 2019), along with active international conferences and symposia in Europe and elsewhere (Dupraz, Gosme, & Lawson, 2019). More scientific publications are appearing in a wider variety of scientific journals in addition to Agroforestry Systems (e.g., Forest Ecology and Management; Society and Natural Resources; Agronomy Journal; Plant and Soil; Sustainability; Agriculture, Ecosystems, and Environment; and the Journal of Environmental Quality).
Previously considered to be a new, interdisciplinary, applied science, agroforestry used to be equated with being professionally “vague” and “non‐rigorous” by many working in more narrow scientific disciplines. However, the biennial NAAC, European Agroforestry conferences (EURAF), and the breadth and depth of the scientific literature are helping to change this situation by raising the professional recognition of those working in domestic agroforestry.
The volume of quality agroforestry research has increased dramatically in the past four decades, helping to support the application of agroforestry domestically. While the science of agroforestry lacks the full spectrum of understanding necessary to assure the successful widespread implementation of most agroforestry practices (e.g., information about specific species’