How little we know

This Backyard Environmentalist column was written over 10 years ago, when I still routinely saw dozens of monarch butterflies in summer and then again in fall.

A great work of literature written thousands of years ago contains a profound lesson for environmentalists. At the end of the book of Job, after Job has worried and wondered and fretted and fumed, for 37 chapters, over the terrible things that have happened to him, God sets him right—by telling him how little he knows about the world: “Have you ever commanded the day to break/ Assigned the dawn its place . . . / Have you penetrated to the sources of the sea,/ Or walked in the recesses of the deep? . . . Have you surveyed the expanses of the earth?” People do not understand the world beyond our own small, everyday concerns, the book implies.

Job doesn’t know how the world works, and therefore he overestimates his own importance in it; 3,000 years later, we do the same thing. We do not understand our place in the natural world, we assume that nature revolves around us, and we do not know the effects our actions have on the environment. Therefore, we often act irresponsibly. But we can learn more and do better.

The natural environment is complicated almost beyond our ability to comprehend. Scientists are just beginning to unravel the most basic interactions among plants and animals. For example, we all love to see monarch butterflies, and many people know that they migrate long distances, winter in California and Mexico, and depend on milkweed plants along the route (plants that some people think of as weeds and destroy). But did you know that monarchs need milkweed only to breed—they lay their eggs on this plant, which is poisonous to most other creatures, and their caterpillars eat only milkweed leaves. However, the adults need other nectar-rich flowers, such as goldenrods and asters, as food sources, so if you plant only milkweed, but destroy a patch of wild asters, you’re not really doing the monarchs much good.

The story gets more interesting. Monarch caterpillars absorb the poisons in the milkweeds, and the caterpillars and adult butterflies are themselves poisonous to most birds and other animals. As a result, monarch butterflies have few predators but many mimics (species that have evolved to look just like them to fool potential predators). Milkweed itself has a complicated ecology: many other insect species, such as milkweed bugs and milkweed beetles, are adapted to live only on milkweed. All of them, like monarchs, have bright orange markings to warn predators. So if you grow milkweed species, as I do, all these critters appear as if by magic (where do they come from, if there was no milkweed in my garden before I planted it?). They chew leavea dnd seed pods, and gardeners don’t like that. But if you zap them with pesticides, you will also kill the monarch eggs and caterpillars. And the critters do very little damage to the plants: the milkweeds (a large group of species) and the many animals that depend on them have coevolved and have a mind-bogglingly complex relationship.

And where do those monarch butterflies come from? In late July, they simply appear in my garden and begin laying eggs on my milkweed plants. I watch the females checking out the plants, looking for the right plants on which to lay their eggs (how do they determine which plants are milkweed species?). Each butterfly flutters slowly over the prairie garden (how do they find this four-foot-wide patch in a sea of lawns?), and when she finds a milkweed, she alights on a leaf. Then she curls her body around beneath the leaf, gently deposits a single tiny egg on the underside, and moves on to do the same again and again. (Imagine if I had used pesticides on the prairie garden.) In early fall, my New England asters attract dozens of migrating monarchs, probably the children or grandchildren of the ones that grew up on my milkweed plants in July.

Unlike most native butterflies, monarchs can’t survive freezing temperatures, even as pupae, so the butterflies we see here in New Jersey are migrating through. From their winter grounds, monarchs migrate north and then south again, some through the midwest and some along the eastern seaboard, all spring, summer, and fall. Each generation lives only a few weeks, and in that time it must find plentiful food (flower nectar) to eat as an adult as well as milkweed plants on which to lay its eggs. The monarchs that arrive in Mexico this winter will be the great-great-grandchildren of the ones that left last spring, and they will find their way to the same roosting tree their ancestors used last year. (Think about all the unknowns comprised just in that last sentence.) One August, on a boat ride to Monhegan Island, ten miles off the coast of Maine, we saw monarchs several miles out at sea, migrating toward the mainland. How do they find that tiny island, or the mainland, for that matter? And once they’ve found the mainland as the first leg of the long trip south, how do they find food all along the way? Every new subdivision threatens them by supplanting the lovely weedy growth they depend on; every new shopping mall can snap the fragile chain that extends through thousands of miles and many generations. Think about that the next time you are annoyed by weeds springing up along the edge of your perfect lawn. Those weeds are food and shelter to some wild creature. (Go to for more information about monarch ecology and biology.)

Monarchs are only one example of the complex interrelationships that exist in nature. Another is our beloved native fireflies. Did you know that firefly larvae eat nothing but slugs? So if you kill slugs, as many people do, you are indirectly killing fireflies. Think about that before you sprinkle salt or diatomaceous earth around your hostas. A few leaves with holes in them is a small price to pay for summerlong fireworks.

Another interrelationship is that between violets and fritillaries, a large family of gorgeous butterflies. Do you routinely zap the broadleaf weeds in your lawn with herbicides? Those “weeds” include violets, most likely. But fritillary caterpillars eat nothing but violet leaves. If you eliminate violets, you’re also killing butterflies. Before spraying that herbicide, think about it from the point of view of the butterflies, or of the birds that eat their caterpillars, or of the ants that collect and spread violet seeds (ants are another complex and fascinating story).

The environment includes not just plants and animals but limited resources like water. The next time you water your lawn, think about where the water will go after it sinks into the ground. Do you know what stream will carry the water away or what body of water it will flow into? If you don’t, you don’t know where the fertilizers and pesticides and fungicides you spread on your lawn will wind up: you don’t know where those chemicals will go, how long they will remain there, what changes they will cause to that environment, what animals and plants they will affect. Lawn fertilizers are a major source of water pollution, and that’s something we can all easily do something about.

The next time you pick up a can of pesticides to zap some bugs that are bothering you, think about the effects of those chemicals. What types of creatures do they kill? Most likely they kill “good” bugs, like ladybugs, fireflies, and butterflies, along with “bad” ones you don’t like. How will those chemicals affect you, your children, your pets, wildlife? All life is related, all life is based on the same chemical structure, so any chemical that can kill an ant can kill you too if you use enough of it. And why do you want to kill those ants on your patio? What harm are they doing, and what benefit might they be providing: What birds are they feeding? Are they perhaps improving your soil by aerating it? If you are killing them to prevent them from coming into your house, are you sure that this type of ant ever does that? Probably not.

Or suppose you see a pretty plant in a garden center, buy it, and plant it in your garden. Do you know where that species came from? If you’re buying it to attract butterflies or other pollinators, is it actually a sterile hybrid that doesn’t produce pollen? If it’s not native, does it have the potential to become invasive and to crowd out important native species? Is there a native species that would be equally beautiful and much better for the environment that you could plant instead? Every alien invasive—Norway maples, purple loosestrife, English ivy, cotoneaster, ailanthus—is a big ecological problem today because the first person who planted it didn’t ask these questions.

And once you start asking, you realize two important things: everything you do has consequences for the environment, and there’s a lot you can do to improve it. Suppose you leave your car engine running in a parking lot because you don’t want to come back to a very hot or cold car. How much gasoline will you use up in that time, and how much carbon dioxide will you release into the atmosphere? Maybe you should just switch off the engine.

We all like to think that we are responsible for our own actions, and we all want to act in responsible ways, but we can’t if we don’t know the consequences of our actions. Because the environment is so complex, it’s sometimes hard to see those consequences. But we can all learn more, consider our actions carefully, and weigh their cost to the environment and to the world we are leaving to our children and grandchildren. We can all do a lot if we act mindfully.