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Darwinian Agriculture

Darwinian Agriculture: How Understanding Evolution Can Improve Agriculture

Copyright Date: 2012
Pages: 248
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  • Book Info
    Darwinian Agriculture
    Book Description:

    As human populations grow and resources are depleted, agriculture will need to use land, water, and other resources more efficiently and without sacrificing long-term sustainability.Darwinian Agriculturepresents an entirely new approach to these challenges, one that draws on the principles of evolution and natural selection.

    R. Ford Denison shows how both biotechnology and traditional plant breeding can use Darwinian insights to identify promising routes for crop genetic improvement and avoid costly dead ends. Denison explains why plant traits that have been genetically optimized by individual selection--such as photosynthesis and drought tolerance--are bad candidates for genetic improvement. Traits like plant height and leaf angle, which determine the collective performance of plant communities, offer more room for improvement. Agriculturalists can also benefit from more sophisticated comparisons among natural communities and from the study of wild species in the landscapes where they evolved.

    Darwinian Agriculturereveals why it is sometimes better to slow or even reverse evolutionary trends when they are inconsistent with our present goals, and how we can glean new ideas from natural selection's marvelous innovations in wild species.

    eISBN: 978-1-4008-4281-0
    Subjects: Botany & Plant Sciences, Biological Sciences, Ecology & Evolutionary Biology, Technology

Table of Contents

  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-vi)
  3. List of Illustrations
    (pp. vii-x)
  4. 1 Repaying Darwin’s Debt to agriculture
    (pp. 1-8)

    This book explores new approaches to improving agriculture, inspired by nature and informed by evolutionary biology. Biologists are nearly unanimous in accepting the multiple lines of evidence that life on earth has evolved and is evolving,¹–³ so applying evolutionary biology to agriculture should be no more controversial than applying chemistry and microbiology to soil science. Yet some implications of past and ongoing evolution for agriculture have often been neglected.

    In particular, I will argue that two popular approaches to improving agriculture have tended to ignoreevolutionary tradeoffs—that is, cases where an evolutionary change that is positive in one...

  5. 2 What Do We Need from Agriculture?
    (pp. 9-27)

    If our goal is to improve agriculture, what do we want to improve? Some important criteria include productivity (yield per acre, to use no more land than necessary), efficiency in the use of scarce resources (to use no more water than necessary, for example), stability over years (to prevent even occasional famines), and sustainability (to maintain all of these benefits over the long term). Improvements in any of these will affect the billions of us who live in cities, both through effects on our food supply and through effects on the availability of land and water for other uses. Other...

    (pp. 28-42)

    This chapter reviews the basic vocabulary and fundamental principles of evolutionary biology. My main focus here is on the power of natural selection to improve the adaptation of individual plants and animals to their environment.

    The power of natural selection and the many millennia over which it has operated are key to one of the central themes of this book:It will often be difficult for biotechnology (genetic engineering) to improve on what past natural selection has already achieved. There are some important exceptions to this claim, however, that will be explored in later chapters. In particular, we may be...

  7. 4 Darwinian Agriculture’s Three core principles
    (pp. 43-53)

    With agriculture’s goals and the power and limitations of natural selection as background, here are three proposed core principles for Darwinian agriculture. A unified field-crop theory would require additional principles from ecology, soil science, and other fields, but these principles and their implications will be the main focus of the rest of this book.

    1. Prolonged natural selection rarely misses simple, tradeoff-free improvements.

    This principle hinges on my definitions ofsimpleandtradeofffree, as explained in the following section, and leads to several corollaries. For example, when natural selection has already balanced tradeoffs in ways consistent with our own goals,...

    (pp. 54-75)

    This chapter discusses the challenge of improving crop resourceuse efficiency, using biotechnology or traditional plant breeding. I use the tradeoff principle from chapter 4 to argue that it will be difficult to improve efficiency more than natural selection already has, unless we pay more attention to tradeoffs. This hypothesis is supported by biotechnology’s failure to deliver on past promises, relative to natural selection’s successes. One human innovation missed by natural selection is discussed, as a possible counterexample. I close with a brief discussion of biotechnology’s risks.

    Plant breeding has traditionally relied on selection of visible or measurable traits.Back-cross breeding,...

  9. 6 Selfish Genes, Sophisticated Plants, and Haphazard Ecosystems
    (pp. 76-94)

    Our second core principle is that competitive testing is more rigorous than testing merely by persistence. This chapter uses that principle, and actual data, to argue that the overall organization of even ancient natural ecosystems may be relatively imperfect, compared to individual adaptations that have been repeatedly tested through competition. Natural ecosystems are still important, however, as the context where sophisticated adaptations of wild species evolved.

    Aesthetics alone can justify preserving natural ecosystems. I would usually rather visit a natural prairie than a corn field, or a natural forest instead of an orchard. Returning to the airport from our honeymoon...

    (pp. 95-119)

    In this chapter, I will discuss four of the most-popular ideas for improving agriculture that have been inspired by nature: perennial grain crops, reliance on only local sources of nutrients,polycultureorintercropping(that is, deploying crop diversity as mixtures, as in many natural ecosystems), and reliance on biodiversity to control pests. All of these were suggested in one classic paper by Wes Jackson and Jon Piper, “The necessary marriage between ecology and agriculture.”¹⁴ I will argue that their ideas are representative of many self-styled “agroecologists.” I will then discuss each of their proposals in light of my conclusion from...

    (pp. 120-144)

    Up to now, I have emphasized the limitations of two popular approaches for improving agriculture. In chapter 5, I suggested that much of the current effort in biotechnology will fail, mainly because it ignores tradeoffs. In chapter 7, I was almost as critical of copying the overall organization of natural ecosystems. The rest of this book has a more positive tone, discussing approaches that have worked in the past, as well as those with unrealized potential.

    While rejecting the extreme positions taken by some advocates of biotechnology and some advocates of “farming in nature’s image,” I am not advocating splitting...

    (pp. 145-163)

    Crop plants often depend on other species for pollination, nutrients, or defense against pests. In this chapter, I discuss some examples of between-species cooperation, the evolutionary tradeoffs that can undermine such cooperation, and opportunities for improvement.

    Cooperation between species might seem even more difficult than cooperation among wheat plants or among chickens, but the opposite may be true. Plants compete with neighboring plants for sunlight, water, and soil nutrients. A plant that takes up more nitrogen than it needs might thereby suppress the growth of a neighbor, which would otherwise compete with it for water. As discussed in the previous...

  13. 10 Stop Evolution Now!
    (pp. 164-176)

    Up to now, I have emphasized agricultural insights from understanding past evolution, but evolution continues today. Weeds and insect pests, in particular, can evolve quickly, with major effects on agriculture. For example, over 180 weed species have evolved resistance to a variety of weed-killing herbicides.³¹⁶ This ongoing evolution will be the main focus of this chapter.

    We have already developed some effective strategies for slowing the evolution of resistance to our pest-control measures. Consistent with our ideas-from-nature theme, we might get additional ideas from studying wild plants and their interactions with the insects that plague them. But let’s start with...

  14. 11 Learning From Plants, Ants, and Ecosystems
    (pp. 177-189)

    We can learn much from natural communities, if we don’t mistakenly assume perfection. Natural selection tends to improve the fitness of each participant in multispecies interactions, regardless of the impact on the community as a whole. Understanding this, can we learn how to optimize such interactions in an agricultural context?

    The previous chapter explained how gaseous chemicals that benefit aphids in one context (warning them of predators) can harm them in others (scaring them away host plants). I will start this chapter with an evolutionary perspective on chemicals as either signals, cues, or manipulation. Then I will revisit the fungus-growing...

  15. 12 Diversity, Bet-hedging, and Selection among Ideas
    (pp. 190-216)

    In this final chapter, I begin by summarizing my main conclusions. Then I will explain the sort of evidence that would make me change my mind. I also consider the possible risks of following my advice, should I turn out to be wrong. In agriculture, as in financial investments, the best insurance against guessing wrong is bet-hedging, by maintaining a diversified portfolio.

    I have argued that the way plant diversity is arranged in natural ecosystems (resembling intercropping) is not necessarily optimal, but that doesn’t undermine the importance of diversity itself. Greater crop diversity, optimally deployed in time and space, is...

  16. Acknowledgments
    (pp. 217-218)
  17. Glossary
    (pp. 219-226)
  18. References
    (pp. 227-248)
  19. Index
    (pp. 249-258)