The world got together to try to save the monarch butterfly, and then climate change ruined the plan

In the winter months of 2015-2016, monarch butterflies had their best migration in years, arriving in record numbers to the Central Mexico forests where they hibernate. Unfortunately, those forests had a really bad year.

Severe storms toppled many of the oyamel fir trees where millions of the iconic orange-winged insects rest after their long trip from Canada. More than 70 hectares of forest were damaged, the biggest loss since the 2009-2010 winter, according to data (link in Spanish) released Tuesday (Aug. 23) by the World Wildlife Fund (WWF). In more bad news, experts expect the butterflies’ overwintering grounds to get hit by this sort of extreme weather more frequently in the future due to climate change.

*This chart shows winter seasons, starting in 2009-2010 and ending in 2015-2016.

The lost habitat is a depressing setback for monarch lovers. There are many along the butterfly’s international route who have been fighting for the monarch’s survival, including the presidents of the US and Mexico. The two countries, along with Canada, have been trying hard to bring back migrating populations to healthier levels after an 80% decline over the last decade.

President Barack Obama last year created a “flyway” along an interstate highway, from Duluth, Minnesota down to the the Texas-Mexico border, to help facilitate monarch migration. The plan involves lining the highway with milkweed, which has been depleted by herbicides used in industrial farming. That flower appears to be the only food picky monarch caterpillars will eat.

In Mexico, the government is working with environmental groups to replace damaged trees, and to get local communities to protect them instead of harvesting them for timber. It’s working, as the chart below shows. (Illegal logging, once the overwhelming reason for forest degradation, accounted for 15% of the lost hectares in the 2015-2016 winter season.)

*This chart shows winter seasons, starting in 2005-2016 and ending in 2015-2016.