Illegal logging in Mexican forests, where the monarchs hibernate during winter, has traditionally been to blame. But large-scale logging by companies appears to have been halted. And now small-scale logging by local people for firewood and timber — a “growing concern in 2013” — has also stopped, according to a study published last month (27 October) in Biological Conservation.
This is partly due to “decade-long financial support from Mexican and international philanthropists and businesses to create local alternative income generation and employment”, it says. Schemes such as community tree nurseries, the growing ecotourism sector and community surveillance of illegal logging have generated new sources of income for local people.
Twenty years ago, around a billion monarchs arrived each year in Mexico. Last year, just 35 million arrived, the lowest number since monitoring began 20 years ago, says Omar Vidal, director of WWF-Mexico, a national office of conservation organisation the World Wide Fund for Nature, and a coauthor of the study.
“Our decade-long research shows that action to stop illegal logging in the monarch overwintering grounds are working thanks to efforts from local communities, authorities, civil society organisations and the private sector,” he adds.
Each year, the butterflies migrate up to 4,500 kilometres from their North American breeding grounds east of the Rocky Mountains to spend the winter — typically from October to March — hibernating in the fir and pine forests of central Mexico.
Until just a few years ago, large-scale illegal logging was devastating the Monarch Butterfly Biosphere Reserve, a 56,000 hectare area of forest established by the Mexican government in 1980. But this has now largely stopped. Between 2001 and 2012, Vidal and his WWF-Mexico colleague Eduardo Rendón-Salinas monitored the amount of forest damaged by illegal logging.
In a study on this research published in Conservation Biology last year, they found that 731 hectares of the reserve were affected from 2005 to 2007. In 2012, thanks to law enforcement and surveillance efforts, none of the reserve was damaged, they reported.
A far greater problem for the butterfly now is the sharp decline in milkweed — the only plant on which its caterpillars feed — in the monarch’s North American breeding grounds, says Vidal.
“It is now time for the United States and Canada to redouble their efforts to protect and restore breeding and migrating habitat within their territories,” he says. “Only then will there be hope that monarchs in North America will recover.”
This view is echoed by 40 leading monarch scientists and 200 organisations and businesses in the United States, who earlier this month (13 November) wrote to the US Fish and Wildlife Service calling for the butterfly to be protected under the Endangered Species Act.
This follows a formal petition in August led by the Center for Biological Diversity, the Center for Food Safety and the Xerces Society for Invertebrate Conservation. Unlike in Mexico and Canada, the monarch has no legal protection in the United States.
“It is now time for the United States and Canada to redouble their efforts to protect and restore breeding and migrating habitat within their territories.”
Omar Vidal, WWF-Mexico
"The biggest threat to monarchs is now loss of habitat in their summer breeding grounds in the United States," Tierra Curry, a senior scientist at the Center for Biological Diversity, tells SciDev.Net.
The cause is the use of herbicides on soya bean and maize crops in these areas in the Midwest, she says. The crops are genetically engineered to be resistant to the pesticide, but milkweed is devastated, she adds.
“Especially at this time of increasing human population and resource demand, and when corporate interests are intent on making huge profits even at the expense of endangered species and their habitat, accurate data [on butterfly migration patterns] is key to gaining and enforcing legal protection for species,” Curry says.
In their recent study, Vidal and Rendón-Salinas say joint action by Mexico, Canada and the United States is urgently needed, and that “only through an immediate, coordinated and well-funded effort that involves politicians, managers, scientists and the public to protect and restore habitat along its migratory route in the three countries” will the monarch be saved.
In Mexico, this will hinge on ensuring local people have other forms of income, and on continuing the on-the-ground surveillance to avoid the resurgence of illegal logging, they say.
> Link to full paper in Biological Conservation
> Link to full paper in Conservation Biology
Biological Conservation doi: 10.1016/j.biocon.2014.09.041 (2014)
Conservation Biology doi: 10.1111/cobi.12138 (2013)