Saving Monarch Butterflies

Monarchs face threats at every phase of their journey. In 1983, the International Union for Conservation of Nature listed monarch migration as an “endangered phenomenon.” The butterflies themselves, while not officially endangered, are in decline.

Climate change is a major threat to monarchs, says Oberhauser. Scientific models predict that as the planet warms, storms that can slow migration and kill overwintering populations will happen more often. Milkweed is the only plant monarch caterpillars eat. The plant’s range is expected to move northward into Canada. If that occurs, the monarchs will need to travel farther north to their summer breeding grounds. In turn, their offspring—the migratory generation—will have to fly greater distances to reach the sacred fir forests in Mexico. There, a drought and warming climate are already affecting the sacred fir trees.

Another huge threat is loss of milkweed and other flowering plants, which adult butterflies depend on to fuel their flight. Growing caterpillars need a lot of milkweed. For every 30 milkweed plants, one monarch lives to adulthood. Unfortunately, modern agriculture is not friendly to the plant, which is considered a weed. Milkweed once grew in corn and soybean fields. But in the late 1990s, people began planting crops genetically modified to tolerate herbicides. “Farmers could spray their fields with herbicide that killed off the milkweed,” Oberhauser says.

Development, like building houses, roads, and farms, also destroys monarch habitat. In Mexico, illegal logging is shrinking the butterflies’ winter habitats.

Monarchs face threats at every part of their journey. In 1983, the International Union for Conservation of Nature listed monarch migration as an “endangered phenomenon.” The butterflies themselves are not officially endangered. But they are in decline.

Climate change is a major threat to monarchs. Scientific models predict that there will be more storms. The storms can slow migration and kill butterflies where they spend the winter in Mexico. Milkweed is the only plant monarch caterpillars eat. The plants are expected to move northward into Canada. If that happens, the monarchs will need to travel farther north to their summer breeding grounds. In turn, their offspring that migrate south to Mexico will have to fly greater distances to reach the sacred fir forests. There, a drought and warming climate are already affecting the sacred fir trees.

Another huge threat is loss of milkweed and other flowering plants. Adult butterflies drink the plants’ nectar as they fly back north. Growing caterpillars need a lot of milkweed. For every 30 milkweed plants, one monarch lives to adulthood. Unfortunately, modern agriculture is not friendly to the plant. That’s because it is considered a weed. Milkweed once grew in corn and soybean fields. But in the late 1990s, people began planting crops modified to resist herbicides. “Farmers could spray their fields with herbicide that killed off the milkweed,” Oberhauser says.

Development, like building houses, roads, and farms, also destroys monarch habitats. In Mexico, illegal logging is shrinking the butterflies’ winter habitats.

Sáenz-Romero has already seen monarchs passing through the sacred fir trees he’s planted. It will be decades, though, before the trees are large enough to shelter the overwintering monarchs.

But you can help the butterflies right now. Planting milkweed and other flowering plants creates monarch habitat, says Katie-Lyn Bunney, education coordinator for the Monarch Joint Venture, a collaboration for monarch conservation. Just make sure that your plants have not been treated with pesticides, which can kill the butterflies. You can also participate in citizen-science projects by reporting monarch sightings to organizations like Journey North and the Monarch Larva Monitoring Project. “A lot of what we know about monarchs is because people are out collecting data,” says Oberhauser.

Sáenz-Romero has already seen monarchs in the sacred fir trees he’s planted. However, it will take years for the seedlings to grow into trees large enough to shelter the monarchs.

But you can help the butterflies right now. Planting milkweed and other flowering plants creates monarch habitat, says Katie-Lyn Bunney. She’s the education coordinator for Monarch Joint Venture, a group for monarch conservation. Just make sure that your plants have not been treated with pesticides first. Pesticides can kill the butterflies. You can also participate in citizen-science projects. You can report monarch sightings to organizations like Journey North and the Monarch Larva Monitoring Project. “A lot of what we know about monarchs is because people are out collecting data,” says Oberhauser.