Fall is the time to plant shrubs and perennials for the next year, and while people are planning, an entomologist wants them to view their garden as a habitat.
Doug Tallamy is a professor in the Department of Entomology and Wildlife Ecology at the University of Delaware and author of four books on nature. His most recent book is The Nature of Oaks: The Rich Ecology of Our Most Essential Native Trees. He started some kind of movement to convince people to give up some of their lawn and plant native trees, shrubs and plants instead.
Kara Holsopple from Allegheny Front spoke to him about it.
LISTEN to the interview
Kara Holsopple: Why should people choose native plants instead of lawn?
Doug Tallamy: There are many reasons. We have to start at the very beginning. We humans are part of nature. We rely on the life support systems nature provides us every day, but the way we design landscapes excludes nature and pretends that we are separate from nature. Lawn doesn’t do any of what we need for any landscape, and there are four of them that I keep talking about: storing carbon, managing the watershed, supporting a food web, and supporting pollinators.
“Lawn does nothing of what we need from any landscape: store carbon, manage the watershed, support a food web and support pollinators.”
Lawn is the worst crop choice for all of this, and we have over 40 million acres of lawn. We have the idea that what happens in parks and nature reserves is good enough. Well, it’s obviously not good enough because we only lost three billion breeding birds in North America. We have worldwide decline in insects. The UN says we will lose a million species in the next 20 years. That does not work. So now we have to do conservation outside of parks and canned goods. That means our private property, and turf is the lowest hanging fruit there is because it is an ecological dead zone.
Holsopple: In your book Nature’s best hope, You introduce the concept of Own national park. What is it and what does it look like?
Tallamy: If we have 40 million acres, and that’s a statistic from 2005, you know we now have more than what if we cut that area in half and transplant it into productive crops to produce these ecosystem services to regenerate biodiversity rather than destroy it? That would give us 20 million acres to spend on conservation where there is lawn now.
“This idea that we are separate from nature is killing us. We are totally dependent on nature. We have to learn to live together because we need ecosystem services everywhere, not just in parks and nature reserves. “
So I start adding, what is 20 million acres? And I’ve added up all the major national parks in the country. It’s bigger than all of them including Denali which is huge. And I said, ‘Well man, we’ll do this at home. Let’s call it Homegrown National Park. ‘ So it looks like that oak tree that is in your front yard. It looks like plantings under this tree, like ground cover, wild ginger, May apple, spring ephemeralies. [It’s] any productive, native plant that is not a lawn.
Holsopple: You mentioned ecological services. Can you say a little more about what that is?
Tallamy: These are all the things that keep us alive on planet earth. How about some oxygen? Pretty important. Plants produce oxygen. How about some clean water? Plants trap the water when it falls from the sky. They slow down its journey to the sea, where it becomes too salty to use. They allow it to penetrate the soil and keep it clean. They prevent flooding.
They don’t have flowering plants unless you have the pollinators that allow them to reproduce. So this is a feedback loop. You need the plants to have the pollinators in order for you to have the plants. But if you don’t have the plants the pollinators specialize in, you don’t have the pollinators.
“If you look at your garden and you have one-thousandth the number of species in your garden that you had before it was your garden, that is the destruction of the ecosystem.”
Native plants also support the food web. This is the one that everyone skips. The titmouse that wants to breed in your yard will need 6,000 to 9,000 caterpillars just to get their babies enough to leave the nest. You feed them caterpillars for another 21 days. You speak of tens of thousands of caterpillars to form a clutch of a tiny bird and think of all the birds out there. These insects come from native plants, not non-native plants that our insects cannot eat because they do not have the adaptations to eat them.
Why do we need these things? Because insects are the little things that rule the world. And why do we need birds? Why do we need the other animals? They are the things that control the ecosystems that provide these ecosystem services. Every time we lose a species from our ecosystem, it becomes more unstable and less productive.
If you look at your garden and you have one thousandth the number of species in your garden that you had before it was your garden, then that is the destruction of the ecosystem. And you know, if you’re the only person doing that, that’s fine. But if we do it over half the country, it’s not okay.
This idea that we are separate from nature is killing us. We are totally dependent on nature. We have to learn to live together because we need ecosystem services everywhere, not just in parks and nature reserves. And we all have this idea that nature is there for entertainment, but that’s about it. This is killing us.
Holsopple: I know there are some Pushback in the ecological world about this intense focus on native plants. Does it have to be all or nothing? Does it have to be all native plants? What about other plants that are not native, belong to the same family as native plants, or behave like native plants?
Tallamy: We have been dealing with this topic for 15 years. So why native plants? Because our insects are adapted to eat native plants. I use the monarch [butterfly] as an an example. It is a host plant specialist in milkweed. You can have the whole crepe myrtle, you can have all the sea buckthorn, all the multiflora rose and all the burning bush and the china berry and all those things that have escaped and supplanted our native plants in our natural areas. And you won’t make a single monarch.
This is true of 90 percent of the insects that eat plants. The ecologists who oppose native plants are not entomologists. They are botanists who don’t look beyond the plant. You’re not looking at the food web. They think if a plant makes a berry, that’s good enough. We need plants that produce the insects and the berries, not just the berries.
“You can have the whole crepe myrtle, you can have the whole sea buckthorn, all the multiflora rose, and all the burning bushes and china berries that have escaped and displaced our native plants in our natural areas. And you won’t make a single monarch. “
Birds do not reproduce on berries, but on insects. 96 percent of birds raise their young with insects. I talk about birds because they are the charismatic megafauna these days. It’s not that they’re the only things that insects eat. Insects are an important part of the food web, even aquatic food webs.
What about non-natives who act like locals? We did a garden experiment together and looked at each other CongenersSo things like Norway maple versus red maple, Norway maple is in the maple family. It’s “Acer”, in the same genus. Does that support as much as our native maples? We did this with generic comparisons and on average, even among conspecifics, closely related individuals, it reduced insect consumption by, what was that, 65 percent? Yes.
So it’s not as bad as if they are not related because then it’s reduced by 78 percent or so. So some insects will eat some non-native people, but it’s nowhere near what we need to have viable food webs.
And my question is what is the benefit? Our main invasive woody plants are all ornamental plants that escaped us by introducing them. And with that we brought a whole host of diseases that have devastated our forests. The cost is exceptional compared to the benefit of being able to use a Chinese facility. There are some exceptions like willows. The species reduction when using weeping willow versus native willow isn’t that much, and crab apples are pretty much the same.
Anything that hybridizes easily with the native means that it is closely related. Insects interact with plants through chemistry, and when the chemistry is so similar that they don’t recognize it, they use it. But most of them don’t. These are exceptions. I keep hearing about these exceptions, but we can’t rely on exceptions because it means the general rule won’t work.
Holsopple: We always have the example of the peony among our employees. Many of us have gardens and are thinking about planting native plants. And last year one of us said what if I just want some peonies in my garden? Can I have a few peonies and the rest native plants?
Tallamy: Yes you can. You know, one of the most important studies we’ve done was done by my PhD student Desirée Narango in Washington, DC, tit population.
So it was a four year study funded by the NSF published in Proceedings of National Academy of Sciences. Tits feed on woody trees, so this is what she looked at. She found that if you exceed 30 percent of the plant biomass in your garden as a woody non-native, the tit population will no longer be sustainable. Then not all birth rates are the same as death rates. So it gets smaller every year. But it suggests that there is an area for compromise.
You can have your ginkgo, you can have your peonies, you can have these other things as long as they don’t exceed 30 percent of the plant’s biomass. And in 84 percent of North America’s counties, there is nothing like oak trees. So if you have one or more oak trees in your garden, your peonies can be yours. It’s okay.
Doug Tallamy is a professor in the Department of Entomology and Wildlife Ecology at the University of Delaware and author of four books on nature.
Resources for native plants
Pittsburgh Parks Conservancy’s Invasive Plants of Pittsburgh Guide
Audubon Society of Western Pennsylvania Native Plant Horticulture
Guide to native plants
List of native plants
List of resources
Pa. Department of Conservation and Natural Resources Info on native plants
List of native plants
Native nurseries in Pa.
Penn State Extension Landscaping for Wildlife
This story is part of our Wild Pennsylvania series. Check out all of our stories Here.
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