North American Agroforestry. Группа авторов

shifts in world weather patterns and the consequences thereof, to the melting of the earth’s glaciers and its ultimate effects on world populations. Humanity has become a victim of its own success. We have conquered the wilderness, and in our attempt to meet the needs of the world’s ever‐growing population, we have endangered many of the ecosystem services upon which our livelihood depends. Our streams and rivers are contaminated with sediment, nutrients and pesticides, mostly products of our success in producing more food at cheaper prices, but also from the privileges success brings such as subdivisions with luxurious lawns requiring large amounts of agrochemicals. Our oceans become the final destination for these and other contaminants, and in combination with the warming of their waters, our oceans too are in a transition towards endangered.

      With today’s understanding of the consequences of current land‐use systems, it is time for a new approach—alternatives must be found. One alternative that was quickly adopted in tropical regions in the 1970’s and 80’s but has been slower in gaining support in the temperate regions of the world, is agroforestry. Agroforestry exploits the positive interactions between trees and crops (including livestock) when they are carefully designed and integrated, they bridge the gap between production agriculture and natural resource management. Supported by four decades of research and demonstration agroforestry practices have been found to provide environmentally and economically sound alternatives to many of our unsustainable forestry and agricultural systems. While if offers opportunities for small farms to regain their relevance and viability it also provides humanity the opportunity to heal our planet by constructively addressing climate change, improving the quality of our air, our waters, and protecting and enhancing soil health.

      The 3^rd edition of North American Agroforestry‐‐An Integrated Science and Practice (now shortened to North American Agroforestry) comes at a critical time as the nations of the world debate the pros and cons of making forestry and agriculture production system decisions based more on economics than on the future health of our planet. In addition to updating the topics found in the 2^nd edition, this edition adds to the science with a new 6th practice of “Urban Food Forests” and chapters on: Agroforestry for Air Quality Benefits; Agroforestry for Soil Health; Agroforestry at the Landscape Level; An Overview of Agroforestry and its Relevance in the Mexican Context and Agroforestry Training and Education.

The chapter authors are all recognized authorities. Their writings, when taken collectively, are meant to provide a state‐of‐the‐art understanding of agroforestry. Agroforestry is rapidly becoming recognized as a science that has great merit in helping address many of our nations’ environmental problems while serving to the economic benefit of our nations’ small farms.

      Harold E. “Gene” Garrett

      School of Natural Resources

      The Center for Agroforestry

      University of Missouri

      Columbia, Missouri

      Shibu Jose

      College of Agriculture, Food and Natural Resources

      University of Missouri

      Columbia, Missouri

      Michael A. Gold

      School of Natural Resources

      The Center for Agroforestry

      University of Missouri

      Columbia, Missouri

Acknowledgments

      The 3rd edition of North American Agroforestry would not have been possible were it not for the assistance of two supporting co‐editors in the preparation of the 1st edition. The current editors express their thanks to W. J. “Bill” Rietveld and R. F. “Dick” Fisher for making this 3rd edition possible. Many hours are spent preparing chapters of the nature found in this text, as is also the case for reviewers who give freely of their time. The editors wish to extend a very special thanks to the authors and dedicated reviewers for their contributions. We also are grateful to Caroline Todd at the University of Missouri Center for Agroforestry for the logistical support she provided during this project.

      The senior editor would be remiss if he did not acknowledge his wife, Joyce, who provided guidance and computer skills in revising and formatting chapters. Without her very capable assistance and encouragement, his job as a co‐editor would have been many times more difficult. And last but not least, to the many contributors to the temperate zone, agroforestry literature, the editors express acknowledgement and appreciation for a job well done!

      This work is partially supported by the University of Missouri Center for Agroforestry and USDA ARS Dale Bumpers Small Farm Research Center, Agreement number 58‐6020‐6‐001 from the USDA ARS.

Section I Agroforestry Fundamentals

1 Agroforestry as an Integrated, Multifunctional Land Use Management Strategy

      Shibu Jose, Harold E. “Gene” Garrett, Michael A. Gold, James P. Lassoie, Louise E. Buck, and Dean Current

      Agriculture is in the midst of a 21st century technological revolution, and we are well into the digital age of farming. The development of agriculture over 10,000 yr, including the technological advancements of the 20th century, has helped push the world population to 7.5 billion, with projections of 9.8 billion by 2050 (Searchinger et al., 2018). While the Green Revolution has helped to feed billions of people, the global environmental footprint of modern agriculture threatens the very existence of the socio‐ecological system in which we live (Funabashi, 2018). The natural resource base, including soil and water, that supports agriculture is experiencing immense pressure. The world is looking for sustainable solutions not only for food security but also for environmental security for the burgeoning population (Searchinger et al., 2018).

      The United States led the agricultural revolution with a massive commitment to enhancing food and fiber production capabilities. The overall strategy was to become self‐sufficient with respect to agricultural crops and timber while improving the health and welfare of rural Americans. Obviously, this was successful within well‐defined limits—today, food remains plentiful and relatively inexpensive, the timber famine was averted, and forest and farm lands abound. Such gains, however, did not come without some high environmental costs, and by the 1970s the public was demanding more environmentally benign land use practices (Laurence, 1987).

      As a consequence of the environmental transgressions committed during the construction of our industrialized nation, new criteria for defining successful land use management strategies were identified during the late 1980s (Turner, 1988). Sustainability, stability, and equability have now joined increased production efficiency as objectives for agriculture (Conway, 1987), and forestry is developing new management strategies that optimize the yield of many products and multiple uses rather than merely maximizing the production of one—timber (Coufal & Webster, 1996; Gillis, 1990; Maser, 1994). But what about the hybrid between agriculture and forestry that is practiced worldwide—integrative management systems far more common than the developed world’s often myopic approach to the production of a limited number of monocultures? Many professionals believe that agroforestry is a strategy for sustainable land use management that might be useful throughout North America (Garrett et al., 1994; Gold & Hanover, 1987; Kremen & Merenlender, 2018; Wiersum, 1990).

As we have moved into the 21st century, concerns have been raised about our dependence on foreign sources of fossil fuels, and the CO₂ emissions from our past and continued use of fossil fuels have increasingly been linked to global warming issues. The production of biofuels and energy from herbaceous and woody biomass has become a major interest with increasing amounts of research funding and private investment. Agroforestry practices combining herbaceous and woody species could play an important role in both the production of biomass for biofuels and energy as well as systems that enhance the ability of agricultural cropping to sequester and store carbon without the ecological problems of currently utilized agricultural systems (Downing, Volk, & Schmidt, 2005; Feliciano, Ledo,