Our blog this week is a letter written by Dr. Doug Tallamy, Professor and Chair of the Department of Entomology and Wildlife Ecology at the University of Delaware, and author of Bringing Nature Home. Written to the New York Times last week:
Subject: Misinterpretation/factual errors in article on Gardening for Climate Change
I am writing to correct the latest error in an article in the New York Times about native and nonnative flora and fauna, and their roles in our ecosystems.
In yesterday’s Sunday Review section, (May 11) an article entitled “Gardening for Climate Change” discussed the value of nonnative plants in urban settings. The author made an error in interpreting the implications of a study by UC Davis, which led him to a wrong conclusion. The fact that butterflies in the urban setting they studied were using nonnatives as host plants does not logically lead to the conclusion that we should plant more nonnatives in our developed areas.
In fact, the study cited is accurate, but the way it’s presented is a bit misleading. All of the butterflies in that study are “specialists” (i.e. they can only metabolize plants in a given plant family). They are using those nonnative ornamental relatives as hosts because their native host has been wiped out. It’s similar to our Black swallowtail using dill as a host. Dill is not native, but it is a close relative of native members of the carrot family. If we take away those natives and provide dill, the swallowtail can’t tell the difference because the leaf chemistry of the dill and the native carrots is nearly identical. This happens, but it is hardly the rule. In suburban California, the only butterflies to survive when the natives are eliminated (which includes most of suburban California) are ones that can use the close ornamental relatives of their native hosts. So, this does happen. However, for every example where it happens, there are 100 examples where it doesn’t.
The author asks, “What’s the big fuss about native plants?” implying that the “fuss” is overblown. But his own example of monarchs needing milkweeds is a perfect example of what the big fuss is all about. If natives weren’t important, monarchs, and the great majority of other butterflies could use any plant. But they can’t. The ones found in the UC Davis study were there because they had some flexibility in what they could eat. The reason most of them can eat nonnatives is not that butterflies are more flexible than we thought; it is that only those few with more flexibility can now survive in areas where there are no natives. (By the way, it is not primarily the weather that has hammered the monarchs, as the author claims. It’s the elimination of milkweed from the midwest farming belt. Because of that, the monarch population has been shrunken to such a tiny size that it is now highly vulnerable to environmental events like weather.)
Frankly, the implication that evolution has made everything OK in our ecosystems is totally false, and it is not helpful to promote that view among your readership. (First, it was Verlyn Klinkenborg (Sept 8, 2013, “Hey, you calling me an invasive species?”), then it was the Ethicist (March 23, 2014, “Should we privilege wild horses?”). And that’s just Sundays.)
Next time you are considering publishing something on this topic, I would be happy to review it prior to publication, or to refer you to someone in the correct discipline to help with fact-checking. It is not a service the public, or to our environment, to propagate the belief that the native v. nonnative issues are over and done with. Unfortunately, the slow pace of evolution and the rapid pace of environmental disturbances means that we are just getting started.
Chair, Department of Entomology and Wildlife Ecology, University of Delaware
Author, Bringing Nature Home
Blog editor’s note: Bringing Nature Home is a book that belongs on the shelves of every person seeking an understanding of why and how native plants play a critical role in the health of our environment. It’s as easy to understand as this letter is. Widely available at bookstores and online.