What's So Great about Native Plants, Anyway?

Another take on the birds and the bees

Did you know that it can take more than 800 caterpillars a day to feed a nest of chicks?  Or that 90 percent of insects, including those yummy caterpillars, can eat only a single type of plant?

©torange.biz

If you did know, then scroll on by. You’re way ahead of me. If you didn’t, then bear with me for a minute as I explain why these facts matter to all of us, and not just to the insect- and bird-lovers in our midst.

First some background. I’m a political scientist by training and an international development nonprofit manager by vocation. Or I was. Until I decided I was ready for a second chapter in my career, this time around in the areas of biodiversity restoration and sustainable landscape design. The point here is that I’m not an expert ecologist, botanist, entomologist, horticulturalist or landscaper. I’m an amateur, and a newbie amateur, at that. There are plenty of people who have dedicated their lives to these subjects and they have my utmost respect and gratitude. I’m writing as a layperson who’s on a steep learning curve, but hoping to share with neighbors, friends and family any interesting observations and discoveries I encounter along the way.

One thing I’ve learned is that I’ve made more than my fair share of ecologically unfriendly decisions in my yard out of sheer ignorance. If I can help a few readers avoid my mistakes or leapfrog straight to contributing to healthier ecosystems in their communities, I’ll be happy.

One more bit of context. The book that launched me on this adventure is Nature’s Best Hope by Doug Tallamy. Much of what I’m sharing here is drawn directly or indirectly from Doug’s research.

Back to the birds and the bees. As humans, we’re wholly dependent on the life-support systems Mother Nature provides. These include producing oxygen, cleaning water, controlling flooding and pests, photosynthesizing, pollinating crops, moderating severe weather, building and protecting topsoil and removing atmospheric carbon. The term for this is “ecosystem services.” Without these functions, we’d be toast.

Once upon a time, when there were fewer humans and lots of undisturbed nature, there were plenty of ecosystem services to go around. And thanks to Teddy Roosevelt and other visionaries, in the US we have a network of national and state parks and preserves to keep parcels of land undisturbed in perpetuity. But unfortunately, these are too small and disconnected to sustain ecosystems to the levels needed. Development swallows more than two million acres per year in the U.S. Since 1985, the Chesapeake Bay watershed has been losing 100 acres of forest to development each day. The national parks are no match for current rates of development.

Also important is that 83 percent of land in the US is in private hands. East of the Mississippi it’s 86 percent. So if we’re going to see more conservation, it’ll have to happen on private land -- which includes farms and ranches, corporate property, and -- importantly -- private homes and yards. That’s where we all come in.

What I didn’t realize until recently is that most plants and animals have specialized relationships with one another. Just one example: monarch caterpillars feed exclusively on milkweed. They’re one of the few species able to tolerate milkweed’s poisonous, milky-looking sap. On the downside, though, monarch caterpillars don’t have the adaptations to eat any other plants. This means that monarch butterflies -- which may sip nectar from a variety of flowers -- will lay their eggs only on milkweed plants. No milkweed, no monarch caterpillars. And no monarch caterpillars means less food for baby chicks and fewer monarch butterflies to pollinate other plants.* Now multiply this example by thousands of other specialized relationships in any given ecosystem. The foundation of an ecosystem is native plants and the insects and other wildlife species that have co-evolved with them. Once you start substituting non-native plants, the whole food web starts to fall apart.

A monarch caterpillar prepares to munch on the leaves of Asclepias incarnata (swamp milkweed) in my backyard

The other thing I didn’t appreciate is how hard bird parents have to work. In North America, caterpillars are the diet mainstay for most birds, especially chicks. It has to do with how squishy and protein-packed those caterpillars are. Like nutritious marshmallows. A typical nestling eats 30 to 40 times a day, meaning a nest of five chicks is expecting mom and dad to make 150 or more meal deliveries a day. The mom and dad can thus hunt only within a small range or they’ll wear themselves out. Given the logistics, they won’t even set up housekeeping if they’re not confident in the foraging prospects. If I had to go to the supermarket 150 times a day you can bet I’d build my nest in the Safeway parking lot.

©torange.biz Meal delivery #139 of the day?

In other words, to support one family of breeding birds, a yard needs to also support thousands of caterpillars. And to support thousands of caterpillars, it needs to contain a large volume and diversity of native plants.

Native plants turn sunlight into energy, create and hold onto soil, store carbon, and soak up water, among other cool feats...their indispensable helpmates are the insects that have co-evolved with them...native bugs pollinate plants, control pests, break down organic matter and provide nutritious meals to other animals that don’t eat plants...the small animals feed the big animals...and around and around it goes...

We depend on the plants and animals indigenous to our specific geographic communities to keep us alive by fueling those ecosystem functions. (If you live in the Bethesda, MD or DC area, that’s the Piedmont region.) But the dependency goes both ways. In order to have red foxes and red-tailed hawks in our neighborhood, we also need to have Eastern redbuds and red chokeberries in our yards. Those foxes, hawks, redbuds and chokeberries are counting on us to keep them alive.

We can’t leave this job to the park rangers and the ecologists. We have to step up, too.

If you’d like to learn more about creating healthy ecosystems in your own yards, please subscribe to this newsletter. I’ll be writing about the whos, whats, whens and wheres of native plants and critters — as I learn them.

Please also let me know what you’d like to hear more about.

Thank you!

*After publishing this article I learned that there’s some debate about whether or not monarch butterflies are actually pollinators.