Scientists have figured out a way to save the monarch butterfly and it involves planting about 1.6 billion new stems of milkweed, which monarchs need for reproduction, to the Midwestern United States.
The eastern migratory population of the iconic monarch butterfly has been decimated in recent decades. The species which breeds in the US and Canada and famously migrates to central Mexico every winter has seen an 84 per cent drop in numbers between 1996 and 2015, thought to be due to a number of factors including climate change, which has produced more severe weather patterns, deforestation in Mexico and, most importantly, the loss of milkweed and nectaring habitat on breeding grounds across Canada and the US.
Milkweed is the only plant that monarch caterpillars eat before developing into butterflies, but since industrial farming began growing herbicide-resistant versions of crops like corn and soy, less wild milkweed is available. Researchers estimate that since 1999, more than 861 million milkweed stems have been lost from breeding grounds in the Midwestern US, which include Minnesota, Iowa, Wisconsin, Michigan as well as parts of Ohio, Indiana, Illinois, Missouri, Nebraska and North and South Dakota.
"The main finding of our study is that an all-hands on deck approach could be essential to restoring the massive amounts of milkweeds needed to make the monarch population healthy again," said Wayne Thogmartin, scientist with the US Geological Survey and lead author of the new report, in a statement.
”These findings offer great hope for citizens from all sectors working together to reverse the substantial decline of these iconic butterflies." Researchers with the USGS, the University of Arizona and other partners created potential scenarios for milkweed restoration involving the re-establishment of over 1.3 billion milkweed stems, an amount which scientists believe would bring the eastern monarch butterfly up to a six hectare-sized population, predicted to be enough to mitigate the threat of extinction. (Monarchs are difficult to count by individuals, so population sizes are measured in terms of area covered in their wintering grounds, with the current estimate at 2.91 hectares.)
The proposed scenarios involved a range of land-use types, including protected grasslands, rights of way along roadsides, areas in or next to agricultural fields and even urban areas such as schoolyards and parks. Researchers looked at the biological potential for milkweed restoration of each type and found that converting half of all the Midwest’s marginal (as opposed to productive) agricultural fields to protected, milkweed-friendly habitats would do the trick.
More likely, though, the researchers found that splitting the 1.6 billion milkweed plants between marginal croplands and other non-agricultural lands is the more attractive option, especially as it would involve more public awareness and participation in the restoration efforts.
"Encouraging urban and suburban areas to participate along with the agricultural sector could create a crucial spark of public support and momentum for monarch conservation across the board," said said Laura López-Hoffman, conservation biologist at the University of Arizona and study co-author.
Many conservation groups have already begun advocating for the planting of milkweed in backyards and gardens both in the US and Canada. Since 2013, the David Suzuki Foundation has been operating a Got milkweed? campaign which offers milkweed seeds for monarch supporters across the country.