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Nature and Nurture From the April 2003 issue of "The Buckeye", the official magazine of the Ohio Nursery & Landscape Association. Joe: Nature vs. nurture? Why that topic this month, Jim? Is this really going to be a discussion of whether genetics or environment play the biggest part in raising our offspring? Jim: Not nature vs. nurture, Joe. Nature and nurture. Your own words belie the dichotomy. “Raising” implies the home environment, “offspring” implies genetics. Its obviously not “either/or”, but rather “both + and”. Lets speak though, not of raising children, but of horticulture. Joe: Okay. For my first sally, here are the words of a sage of antiquity, Horace: Naturum expelles furca, tamen usque recurrat. You can drive out nature with a pitchfork, but she always returns. Jim: Without a doubt, nature tends to have the last laugh or cry; horticulturists who ignore natural processes do so at their own peril. However, the very word “culture” in “horticulture” implies our desire to modify nature. Joe: But have you not heard: “Man makes mistakes; nature doesn’t.” Isn’t that what natural selection is all about? If natural selection works for the best forms and most balanced interactions that could possibly exist in any one spot, then native must be best. Jim: What leaps of logic and topic. I see you are handing me the points the late Stephen Jay Gould counterpoints in his essay on “An Evolutionary Perspective on the Concept of Native Plants”. Gould argues that natural selection does not mean that whatever is found in nature at any given point is the optimal “natural” rightness of what should be living in a particular environment. Gould says: “The evolutionary fallacy in equating native with optimally adapted can be explicated most clearly by specifying the central theme of natural selection as a causal principle. As Darwin recognized, and stated so forcefully, natural selection generates adaptation to changing local environments - and nothing more...Many native plants evolved from natural selection as adaptive to their regions, fare poorly against introduced species that never experienced the local habitat. If natural selection produced optimality, this very common situation could never arise, for native forms would prevail in any competition against intruders.” Gould argues that the idea that native must therefore be right and best because God made each creature to dwell in its proper place is not what natural history shows us; plants grow not just where they are most “appropriate” - there is considerable chaos, contingency and randomness involved. Joe: But wait, Jim. Those intruders are a big problem. Let me broaden the issue a bit to discuss not just native plants, but also native insects. Consider the example of the native bronze birch borer insect and its interaction with birches native and non-native to the U.S. As Dave Neilsen has shown through the birch plantings at OARDC in Wooster, over several decades, native birches fare much better than non-native birches against this native insect. Exotic birches such as the European white birch and Monarch birch are much more infested (they died much sooner) than native birches such as gray birch, Betula populifolia and river birch, Betula nigra, the latter of which is essentially not affected at all in the plot. This is a strong argument for use of native birches... Jim: ... No argument... Joe: ...Why, even consider your beloved disease triangle and the case of Dutch elm disease. In the early 1920s, elms susceptible to the pathogen Ophiostoma ulmi were abundant here, and the environment was conducive to disease, but we did not see Dutch elm disease in the U.S. because the pathogen was not here. Then elm logs brought over from Europe were infested with O. ulmi (with the assistance of their vector, European elm bark beetles, I might add), and voila - the non-native pathogen had arrived and we had problems on our native American elms... Jim: ...No argument... Joe: ...And have you no sympathy for the grounds manager having to deal with the invasive alien weed species garlic mustard, and... Jim: ...Joe, I have no argument with the fact that invasive non-native (and native) insects, fungi, and plants are a problem for landscapes and woodlands and wetlands and people in the U.S. and everywhere else. I am simply arguing that we must get beyond the idea that natives at any given point in time are somehow best adapted or best suited or most ethical for a particular niche. Would or should you really be willing to give up our Ohio vegetable gardens with their pre-European colonization non-native tomatoes, corn, lettuces, garlics, green peppers, and on and on? Non-natives all, a product of human horticultural efforts. Not to mention the fact that there were no well-weeded vegetable gardens naturally growing in pre-European colonization woodlands and prairies. Humans, with all our propensity for mischief at times, are after all part of nature and their modification of nature is not inherently un-natural.. Joe: Naturum expelles furca, tamen usque recurrat. Jim: Of course. We must never drive out nature with a pitchfork; we need to understand nature better and use our horticultural tools wisely, to learn the sensitive cultivation of plants as Gould says, rather than starting from the premise that native is morally best. Gould quotes Rudolph Borchardt in his essay. Borchardt was reacting to the incredible extreme of nativism argued for by the Nazis and their call for horticultural use of only Aryan plants: “If this kind of garden barbarian becomes the rule, then neither a gillyflower nor a rosemary, neither a peach-tree nor a myrtle sapling nor a tea-rose would ever have crossed the Alps. Gardens connect people, times and latitudes. If these barbarians ruled, the great historic process of acclimatization would never have begun and today we would horticulturally still subsist on acorns. The garden of humanity is a huge democracy.” Within the context of native and non-native, as Gould points out, “Homo sapiens after arising in Africa, seems able to prevail in any exotic bit of real estate, almost anywhere in the world!...Do we become more “democratic” when we respect organisms only in their natural places (how then, could any non-African human respect himself?” Our natural challenge must be to learn and study and do the best we can to determine which non-natives and natives are invasive and best to prevent and control from damaging natural areas and landscapes. Gould paraphrases another sage of antiquity, Plato, who urged that “art” should be defined as the caring, tasteful and intelligent modification of nature for respectful human utility. Without a doubt, as you say, Joe, “Man makes mistakes”. The journey is ever imperfect. Blending nature with nurture, not nature vs. nurture, though, is the goal. As Michael Pollan writes: “Up with multihorticulturalism!” Jim Chatfield and Joe Boggs |