Two years ago, the monarch butterflies came by the dozens. The hundreds. Here on Long Island, we sat on the beach in September and watched them flutter west all day long. They were following the edge of the ocean on the way to their wintering grounds thousands of miles away in central Mexico. The next fall, we saw none.
Monarchs migrate. The eastern butterflies complete one of the longest, most complicated migrations in the world, starting from high mountain forests in central Mexico where the population spends the winter. In the spring, the monarchs wake from hibernation, mate, and fly north. This generation pushes as far as Texas, laying eggs as they go. Then, after a few short weeks of flight, they die. Their babies continue the northward journey as soon as their wings are dry. It takes three generations, three cycles of mate-fly-lay-die, for monarchs to cover the continent east of the Rockies. The fourth generation hatches at the end of the summer. These monarchs are born with different instructions, and a genetic compass that points them south.
The fourth-generation butterflies travel to the exact same forests where monarchs have wintered for thousands of years, even though they've never seen them. Not a one stops to ask for directions.
When the monarchs arrive at their destination, they line up, warm fuzzy body next to burnt orange wings, along every branch of every tree. They cluster close for warmth. The effect is a forest breathing in butterflies.
I've had just a taste of what it might feel like to stand in those butterfly forests. That September two years ago, I passed a small grove of pine trees by the beach just as the sun was setting. I noticed the trees seemed animated, stirring like a sleeping animal, though there wasn't any wind. When I stepped into the grove for a closer look, the branches burst into wings. The stream of migrating butterflies had paused for the night, weighing down the limbs with their velvety bodies just as they would in another few weeks, another few thousand miles.
That may be the only chance I'll ever have to see them.
The population of monarch butterflies that migrates through eastern North America has been declining for 20 years, but after steep drops several years in a row, the monarchs are now in serious trouble. Researchers in Mexico count the wintering monarchs by how much forest they fill. This past January, they announced lowest coverage of butterflies on the wintering habitat in 20 years. The butterflies covered just 0.67 hectares, down from a high of 21 hectares, a 43.7 percent decline from the year before. Only about 30 million butterflies arrived to winter in the forests.
Of the many problems that might contribute to the monarchs' decline, one stands out: milkweed plants, the exclusive food of monarch caterpillars, are disappearing as fast as the butterflies. Development and changing agricultural practices in the corn belt have eliminated about 30% of the monarchs' breeding habitat, around 167 million acres of land, since 1996. Today, monarchs could travel several hundred miles of their northward journey and not find any milkweed on which to lay eggs. For many, it's just too many miles to the next milkweed plant and they die without laying their eggs.
The prospect is grim. But there's some good news: we can plant more milkweed.
We can buy seeds and plants for our yards. We can share them with our friends and neighbors. We can encourage our towns and counties to let medians go fallow, and we can fill the space with milkweed and other native plants. We can ask park districts to set aside more habitat for butterflies, and encourage utility companies to cultivate their right-of-ways to benefit monarchs and other pollinators.
Ideally, the butterflies would find a corridor of milkweed from Mexico to Canada, a highway for the adults, a buffet for caterpillars. We can't create it instantly, but we can all help make it a reality in the next few years, one backyard and highway median at a time.
The butterflies have already left the mountains in Mexico, but there's still time to plant milkweed to fill the gaps as their descendents continue north. You can find milkweed seed and plants for your backyard or community garden through native plant societies, Audubon Society groups and state cooperative extensions. Project Monarch Watch has spent the past year growing thousands of milkweed plants from seed to feed this year's butterflies. You can order flats of milkweed at http://www.monarchwatch.org/ or visit https://www.livemonarch.com/free-milkweed-seeds.htm to request free milkweed seeds.