There's a reason why the incredible Monarch Butterfly was featured on one of our Nature Blows My Mind columns. The species makes a 2,500 mile annual journey that takes four generations of butterflies to complete. That's right, four generations of butterflies are born, live their life, and die as the species continues the annual migration.
An Incredible Journey for a Small Insect
Millions of monarchs make the trip from northern areas of the North American continent south to California and Mexico. The first three generations of monarchs live anywhere from a few weeks to two months. But the fourth generation born at the end of summer enters a phase called diapause, where they do not reproduce and can live for seven to eight months. It is this fourth generation that spends the winter months in the south before beginning the journey north as the weather warms in February or March.
What is really amazing is that these butterflies typically use the exact same trees each winter that their great-great-grandparents used. They were never shown which trees to cuddle up in, yet they somehow know and return to the very same trees every year without fail.
This return to a very specific place is actually part of what puts the species in danger.
Illegal Logging and Roundup-Ready Crops
Monarch Joint Venture reports that the Eastern North American monarchs that travel to the same locations in Mexico every year face habitat loss from legal and illegal logging, land conversion for farming, and climate change -- all of which destroy or alter the microclimate and habitat the species needs to survive the winter. Meanwhile, Western North American monarchs that travel to the same locations in California every year also face a downward trend that, while it is not fully understood, ties partly back to habitat loss from municipal and commercial development.
But loss of a place to over winter isn't the only threat.
As reported by The Kansas City Star, "The monarchs' numbers have been cut in half in recent years, some researchers say, and they put much of the blame on hardier farm crops here in the Midwest. Monarchs lay their eggs on milkweed plants. But thanks to genetically modified corn and soybeans that withstand herbicides, farmers can now wipe out milkweed from their land without damaging their crops. That means monarchs can no longer find milkweed on 100 million acres of farmland."
Without food, monarch butterflies face decline throughout the year. But importantly, without a safe place to overwinter, this fourth generation of butterflies responsible for returning the species north for the spring may not survive to return at all. Sanctuaries that protect trees where monarchs return are one of the most important things keeping the species from disappearing entirely.
There are more than 300 overwintering sites where monarch butterflies return each year in California alone, ranging from north of San Francisco to south of Ensenada, Baja California. Sanctuaries have popped up along the coast to protect some of these spots, including Pacific Grove, Santa Cruz, and Pismo Beach. Additionally, several sanctuaries have also been set up in Mexico, including the famed Monarch Butterfly Biosphere Reserve which is also a World Heritage Site. These sanctuaries are a paper-thin wall that help protect the butterflies from what would quickly turn into a mass die-off if not complete extinction.
But even with these sanctuaries, the butterflies are imperiled by how we farm.
As reported recently by the Associated Press, "A new study of the Monarch butterflies' winter nesting grounds in central Mexico says small-scale logging is worse than previously thought and may be contributing to threats facing the Monarch's singular migration pattern. The reserve's 33,482-acre core zone lost 41 acres of pine and fir trees so far in 2013, about half of that because of illegal logging, said the study by Omar Vidal, head of Mexico's chapter of the World Wildlife Fund, the WWF, and other authors. The rest of the loss was due to drought or disease-control removal of trees... The Monarch migration is under serious threat. A report in March said the number of butterflies making it to Mexico this year had dropped 59 percent, the lowest level since comparable record-keeping began 20 years ago. It was the third straight year of declines for the orange-and-black butterflies. Six of the last seven years have shown drops, and there are now only one-fifteenth as many butterflies as there were in 1997."
The Washington Post just reported, "Last winter, just 60 million butterflies arrived at their overwintering habitats, a record low. And early signs suggest that this winter's population might be even lower — though, do note, we're still awaiting final numbers."
How to Support Monarch Butterflies
If monarch butterflies are in your area, support them by providing milkweed plants in your garden, which are their food source and where they lay eggs for the next generation.
You can also help monarch butterflies by supporting one of the several sanctuaries set up for them in California and Mexico to protect the trees to which they return every year as well as the surrounding trees necessary to create the microclimates the species depend upon. You can help these sanctuaries ensure the butterflies have somewhere safe to overwinter before beginning their incredible journey north again.
As Monarch Joint Venture notes, "While increasing awareness of monarchs and their decline can help to boost conservation efforts, increasing tourism inspired by monarchs can drive an increase in development and pollution near overwintering sites, which can have harmful effects on overwintering clusters."
So, if you needed an excuse to go see the incredible phenomenon of millions of overwintering monarch butterflies, you couldn't ask for a better one than "I'm helping to save the species."