To many, Doug Tallamy needs no introduction. A renowned ecologist, his 2020 NY Times Best Seller, Nature’s Best Hope, showed homeowners how to turn their yards into conservation corridors. His latest book, The Nature of Oaks, was released in March 2021. Here he offers a message specifically written for Turf readers about why we should be planting more oaks.
In case you haven’t heard: life on Earth is in trouble. Distressing statistics about declining biodiversity are being reported so fast they are running into each other. North America has lost three billion breeding birds in the last 50 years; Earth has lost 45% of its insects with continuing declines reported nearly everywhere; and the UN predicts one million species will go extinct in the next 20 years. Not only are we in the midst of the sixth great Earth extinction event, but loss of populations in species not yet extinct is rampant. We hear much about the climate crisis, and rightly so. What many fail to appreciate is that our disregard for the well-being of biodiversity is as grave a threat to humans as climate change, because it is healthy, productive ecosystems—not Best Buy or Costco—that support us, and it is biodiversity that makes ecosystems healthy and productive. To put it bluntly, we are destroying the natural world that we cannot live without.
It’s not that we purposefully have nature in our sights. Rather, we have simply refused to share our spaces with the natural world. We have clung to the notion that humans and nature cannot coexist as if it were true (it’s not). And so, as our population has expanded, we have exiled nature to parks and preserves that are too small, too few in number, and too isolated. The grim statistics cited are a stark reminder that our protected lands (just 12% of the U.S.) are not sufficient to sustain the amount of nature our ever-growing populations require.
Four Landscape Imperatives
Fortunately, there is a solution to this existential crisis. We can save nature by learning to live with it. Rather than practicing conservation only within parks and preserves as we have done in the past, we must now also conserve nature outside of protected places, where we live, work, shop, farm, and play: that is, in built, human-dominated landscapes. There are four roles every landscape must play if we are to forge a sustainable relationship with the natural world that supports us.
- We must landscape with plants that support local food webs, for it is the transfer of energy from plants to animals that enables the animals that run our ecosystems to exist.
- All landscapes must pull CO2 from the atmosphere and store the carbon first in plant tissues and then long-term in the soil.
- All landscapes must help manage the local watershed. No one has the ethical right nor ecological permission to design a landscape that degrades its watershed.
- Finally, all landscapes must nourish a complex community of native pollinators by supplying the pollen and nectar they require to successfully reproduce.
This is where the mighty oak can help. Oaks accomplish three of these four essential landscape roles better than any other tree genus in North America. By adding one or more oaks to our yards, our corporate landscapes, our round-abouts and cloverleaf interchanges, and public parks, we can: support more animal species in higher numbers; sequester more CO2 by virtue of their large size, great age, and densely packed xylem cells; and improve our watersheds more quickly and thoroughly than if we choose other tree species (or no trees at all) due to their large crowns, immense root systems, and long-lived leaf litter.
The only thing oaks do not do better than other plants is support pollinators (oaks are wind pollinated), but three out of four isn’t bad.
Why are oaks best at helping animal populations? Two reasons: they serve as host plants to more species of caterpillars than other trees, and they produce large sources of fats and proteins in the form of acorns—up to three million acorns in the life of a single oak tree. The importance of acorns in supporting jays, titmice, towhees, chipping sparrows, nuthatches, woodpeckers, turkeys, ducks, rodents, squirrels, deer, and bears is self-evident; acorns are produced in the fall, right when these creatures need to store fat for Winter survival.
Beyond birds and animals, caterpillars are every bit as important in our landscapes, though the reasons are not so evident. Think back to grade school biology when we learned about photosynthesis. To be sure, plants are beautiful landscape decorations, but in terms of nearly all animal life on earth, plants are far more. They are the only life forms that, through photosynthesis, can turn light energy from the sun into food. Plants enable us and every other animal species to “eat” sunlight. But unless an animal has access to the food that plants make, it doesn’t do them any good at all.
How do most animals get plant energy? Not by eating plants themselves, as you might think, but by eating something that ate a plant. Most vertebrates do not eat plants directly; they eat insects that ate plants. And not just any insects. In most ecosystems, it’s caterpillars that transfer more energy than any other plant-eater.
Take birds, for example. Most (96%) of the terrestrial bird species in North America rear their young on insects, and in 16 out of the 20 most common bird families, caterpillars dominate nestling diets. And not just a few. Typical birds, like Carolina chickadees, require 6,000 to 9,000 caterpillars (depending on the number of chicks) to raise nestlings until they leave the nest. Parents then continue to feed caterpillars to their young for another 21 days after fledging. It takes well over 10,000 caterpillars to make one clutch of a bird that weighs 1/3 of an ounce, four pennies worth of bird. And chickadees are not exceptions. Most birds rely just as heavily on environments that produce huge numbers of caterpillars.
My point is simple: if we want robust populations of birds to be able to breed in human-dominated landscapes, we need to create landscapes that produce lots of caterpillars. Choosing plants that support many caterpillar species is a must, then, and no plant genus supports more species of caterpillars than Quercus, the oaks. In fact, oaks are the primary host for more than 950 caterpillar species nationwide. To put this extraordinary ecological accomplishment in perspective: in the Mid-Atlantic, native tulip poplars support 21 caterpillar species, crepe myrtles support three, and gingkoes support none. A yard landscaped with typical Asian ornamentals has no chance of producing the insect food birds need to reproduce.
Oaks At Risk
Despite these vital attributes, oaks are in trouble. The old giants that provided unique niches for layers of biodiversity are now largely absent from our landscapes. Oaks were prized suppliers of wood products and most large specimens were logged centuries ago. Long after the giants were gone, we continued to degrade oak habitats across the country. Vast tracks of oak forests have been ‘developed,’ converted to crop or pastureland, or have been highly altered by fire suppression. In fact, the oaks in eastern forests has dropped from 55% pre-European settlement to 25% today. Add pressure from the climate collapse that favored oak health over 8,000 years, as well as the human introduction of sudden oak death, oak wilt, and oak leaf scorch, and invasive pests like the gypsy moth, and many oak species are now on the ropes. An analysis by Morton Arboretum in Lisle, IL has found that 28 of the 91 oak species in North America (over 30%) are so diminished in numbers, they may soon disappear from the wild forever.
We humans live our lives out in a brief instant of ecological time. We cannot return ancient oaks to our landscapes during that instant, but we can (indeed, we must) start. I’ve planted a number of massive old oaks on our property, except they are only 20 years old and not so massive yet. They are growing, though, and several have topped 50′ at this writing. In a blink of time they will be large enough and old enough to assume their keystone positions in our yard.
HOMEGROWN NATIONAL PARKS
“…what if each American landowner converted half of his or her yard to productive native plant communities? Even moderate success could collectively restore some semblance of ecosystem function to more than 20 million acres of what is now ecological wasteland.” —Tallamy
Homegrown National Park®, a term coined by Doug Tallamy, is a call-to-action catalyzing the collective effort of individual homeowners, property owners, land managers, and anyone with some soil to plant in, to start a new HABITAT® byplanting native plants and removing most invasive plants. The idea is to regenerate biodiversity and ecosystem function and create new ecological networks.
In Tallamy’s words: “Our National Parks, no matter how grand in scale are too small and separated from one another to preserve species to the levels needed. Thus, the concept for Homegrown National Park, a bottom-up call-to-action to restore habitat where we live and work, and to a lesser extent where we farm and graze, extending national parks to our yards and communities.”
The HNP’s initial goal is 20 million acres of native plantings in the U.S. This represents approximately ½ of the green lawns of privately-owned properties. Progress is tracked in an interactive community-based visual map that shows each person’s contribution to planting native by state, county, and zip code. There’s also a gauge showing progress towards the goal. The map is also an important way for individuals to see their part in the greater whole–creating new ecological networks and restoring biodiversity. For more information, visit homegrownnationalpark.org.
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 106 research publications and has taught insect-related courses for 41 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. Besides the aforementioned books, he has written Bringing Nature Home, and The Living Landscape (co-authored with Rick Darke). His awards include recognition from The Garden Writer’s Association, Audubon, The National Wildlife Federation, Western Carolina University, The Garden Club of America, and The American Horticultural Association. Doug lives with his wife, Cindy, on their restored property in Oxford, PA.