The eastern population of monarch butterflies seems to like spending the winter months high above sea level There they can hibernate until spring The oyamel fir forests in Mexico have just the right climate for monarch butterflies It’s cold but not so cold that they must use their fat reserves to survive The moisture from humidity helps to keep them healthy And the trees are big and strong enough to support millions of butterflies as they gather for the winter Some monarch butterflies fly as far as 3,000 miles 4,828 kilometers to reach these special places Monarch butterflies on their way to their winter habitat rest on the pines and eucalyptus trees in Monarch Grove Sanctuary in Pacific Grove California 6
But in recent years tourism and logging has taken away much of the monarch’s winter habitat And in the United States their food supply has been depleted because of the use of herbicides Scientists such as Lincoln know that monarch butterfly caterpillars only eat one thing milkweed Milkweed protects the caterpillars from being eaten by birds or other predators because to them milkweed is poisonous The brightly colored monarch butterfly caterpillars only eat milkweed Their bright colors are a warning to predators that they are poisonous FIELD NOTES The Mexican government recognized the importance of oyamel fir forests in 1986 They created the Monarch Butterfly Biosphere Reserve for monarch butterflies 7
Milkweed was once abundant in the prairies across the Midwestern United States Milkweed used to be a common wild plant in the prairies across the Midwest It continued to grow along with planted vegetable crops but was considered a weed Farmers sprayed milkweed and other plants with herbicides In order to grow more crops farmers developed herbicide-resistant seeds They could now spread herbicides over a much wider area without killing the crops too With the loss of milkweed monarch butterflies had no place to lay their eggs Lincoln believed that climate change was also affecting the survival of these creatures 8
In 2014 Lincoln filed the first petition to have the monarch butterfly listed as threatened under the US Endangered Species Act If the insects get the protection Lincoln has more plans for them He wants land to be set aside for their food supply He wants incentives for farmers not to put weed killer on all of their croplands Even if counties would just wait until after the frost to mow the roadsides that would make a big difference Lincoln said And he hasn’t stopped there In order to track illegal logging in the roosting grounds Lincoln formed a Geographic Information Systems team Students and professionals from the University of Mexico NASA and Sweet Briar College work together to monitor logging activity He also participated in conservation efforts to help local populations preserve and protect their forests where the butterflies roost FIELD NOTES The Center for Biological Diversity estimates that monarch butterfly numbers have gone from a billion to only 35 million in recent years Their numbers seem to dwindle each year 9
