Helping Nature Take Its Course By Doug Tallamy
Helping Nature Take Its Course
By Doug Tallamy
The natural world we encounter today is not the same world we would have encountered 500 years ago, 100 years ago, or even 20 years ago. When I was a boy (60 yrs ago), I could count on finding a box turtle, a spotted turtle, and several species of salamanders any summer day on a walk through a nearby woodlot. I would have kicked up scores of grasshoppers in the meadow I crossed before I reached that woodlot, and I never worried about picking up a deer tick because I didn’t know what a deer tick was; I had explored those fields and woods for years without ever encountering one. If I saw a white-tailed deer, it would have been a very special day, for they were rare in north central New Jersey where I grew up. I didn’t know much about plants, but nearly all of the species I walked by in those days were native to North Jersey. I still remember my first encounter with invasive multiflora rose shortly before I moved from the area. I was used to running pel mel through the meadow, bursting through tangles of vegetation without a scratch. But not that day. I ran full speed into this new bush I had never seen before and got sliced to ribbons for my troubles. Little did I know that that invasion was just the first of many more to come as the ornamental plants used in the surrounding yards escaped cultivation and took over my early stomping grounds.
Today were I to ramble behind my old neighborhood, I would find no box turtles and the woodland pond that was home to spotted turtles and the breeding ground for local salamanders was long ago filled in with old refrigerators and air conditioners. I would not be able to spend an afternoon in the woods without meeting several deer and the deer ticks they support, and most of the understory shrubs, trees, and vines would be non-native autumn olives, barberries, Callery pears, Amur honeysuckles, Norway maples, Ailanthus trees, oriental bittersweets, privets… and, of course, those thorny multiflora rose bushes.
As I speak to the public about why these ecological changes are a primary cause of the declines in native species that are regularly headlined today, and how such declines threaten ecosystem function and thus the production of our life support systems, I am often asked why we don’t just let nature take its course to bring white tailed deer populations back below destructively huge sizes; to control the tick populations and the Lyme disease they transmit that have swelled along with the deer; to control the invasive plants that have escaped our gardens to run amuck in our natural areas, replacing native plant communities as they spread. In other words, why can’t we let nature fix all of the ecological threats we humans have unleashed on earth’s biosphere? This question goes hand in hand with a related query; is it wise for us to interfere with natural competition among plants and animals? After all, I am told, if invasive plants are more competitive than natives, better at living in North America than the plants and animals that evolved here, shouldn’t we just sit back and let them win? And finally, there is the philosophical question regarding our right as mere human beings to “play God” and decide what lives and what dies.
These are all good questions and fortunately they have good answers. Let’s start with why we can no longer rely on natural processes to control deer, ticks, and invasives. Believe me, I wish we could, because nothing would be easier or more cost effective than letting nature mend all of those human-inflicted ecological wounds. We can’t let nature take its course, though, because she is no longer able to. Quite simply, we have removed the means by which nature used to restore balance in disturbed ecosystems. In the case of invasive species, we have created unnatural competitive interactions by importing plants, insects, mollusks, reptiles, birds, mammals and diseases from other continents without any of their natural enemies. This gives invasive species a huge competitive advantage over our native species whose populations are tightly regulated by dozens or hundreds of natural enemies. Throughout most of the country we have eliminated the wolves, cougars and bears that used to keep deer populations in check. In fact, unnaturally high deer populations further tip the balance against native vegetation because deer prefer to eat native plants over Asian species. This has become such a serious issue that U.S. Forest Service Botanist Tom Rawinski claims with much evidence that unregulated deer populations are a greater threat to eastern forests than climate change.
In short, by eliminating the mechanisms by which mother nature used to take her course, we have, in essence, tied her hands behind her back. She no longer has the means to correct the imbalances we have created. Non-native invasive species are not superior beings that deserve to win competitive interactions with native species. They are plants and animals we humans brought to our shores simply because they were pretty, or because they were accidental hitchhikers as we moved products around the planet far faster than organisms can adapt to new comers.
As to whether we have the ethical right to decide whether a plant or animal lives or dies, I could easily argue that we do not have that right. Although it would be hard to find someone who did not believe humans are superior beings and therefore more important than any other species, I can assure you that lions, toads, houseflies, and earthworms feel the same way. The reality is that even those who question our inherent right to manage invasive species make decisions about what lives and dies every day. Every time you choose to plant a non-native species over a native plant, you are deciding whether the chickadee in your yard can feed its babies or watch them starve to death because there aren't enough caterpillars? Every person who installs or continues to maintain acres of lawn is inadvertently deciding whether hundreds of species of native plants and the thousands of animal species those plants support will live in that space or whether they will be replaced by one species of European grass. Every person who hires Mosquito Joe to fog his or her property is condemning not just mosquitoes, but all of the butterflies and bees on their property to death as well.
The real question is, on what basis should we decide how to manage our landscapes? I think the best approach is to base such decions on how they will affect the greater good. For example, if I plant porcelainberry, a highly invasive Asian ornamental, I have inadvertently sentenced generations of native plants to death, because the seeds of that plant will escape from my yard and overgrow just about anything in its path. The same applies to other invasives like privet, buckthorn, cheatgrass, Himalayan blackberry, burningbush, autumn olive, kudzu, Amur honeysuckle, Japanese barberry, Callery pear, etc, etc, etc. Invasive plants are ecological tumors that spread continuously unless checked by us or some environmental factor. And everywhere they spread, they are killing the native species that run our ecosystems.
If you are diagnosed with a cancerous tumor, I doubt if you would ponder whether it is ethical to kill those tumor cells in order to save your healthy cells. In the same way, once invasive plants are established, we have to decide whether to remove them (kill them) or not. If we do remove them, we are opening space for hundreds of species of native plants and thousands of species of the animals that depend on them. That is, we are providing opportunities for life. If we don't kill the invasives, we continue to starve our birds, shrink the distribution of native plants, and further compromise the ecosystems that support us. I wish we could let mother nature take its course, (which, by the way, includes life and death interactions all day long), but when we by-pass the hard won evolutionary checks and balances that have kept communities of plants and animals in balance since life evolved some 3 billion plus years ago, we have shackled mother nature. She can no longer take her course within reasonable time frames. We have created conditions that require us to manage the landscapes around us for the greater good. That is, we have created conditions that now demand we garden the world, which means we have to decide which plants live and which ones die. If we make those decisions wisely, more species will live. if we make them foolishly, more will die.
Doug Tallamy is the T. A. Baker Professor of Agriculture in the Department of Entomology and Wildlife Ecology at the University of Delaware, where he has authored 104 research publications and has taught insect related courses for 40 years. Chief among his research goals is to better understand the many ways insects interact with plants and how such interactions determine the diversity of animal communities. His book Bringing Nature Home was published by Timber Press in 2007 and was awarded the 2008 Silver Medal by the Garden Writers' Association. The Living Landscape, co-authored with Rick Darke, was published in 2014; Nature's Best Hope, a New York Times Best Seller, was released in February 2020, and his latest book The Nature of Oaks was released by Timber press in March 2021. Among his awards are the Garden Club of America Margaret Douglas Medal for Conservation and the Tom Dodd, Jr. Award of Excellence, the 2018 AHS B.Y. Morrison Communication Award and the 2019 Cynthia Westcott Scientific Writing Award.
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