The Monarch butterfly population is shrinking due to illegal logging in Mexican forests and herbicides used in Canada and the United States along its migration route, said a new study.

The orange and black butterfly travels from Canada every year to hibernate in central Mexico between November and February, but its population is showing a "clear downward trend," said Omar Vidal, director of the World Wildlife Fund's Mexico office.

A total of 2,179 hectares of forest was lost in its winter homes in the states of Mexico and Michoacan between 2001 and 2013, Vidal told a news conference on Monday to present the study published in the journal Conservation Biology.

In the 2012-2013 season, the hibernating colonies occupied an area of 1.19 hectares in the 56,259-hectare reserve, the lowest area occupied by the species in 20 years, he said.

Over the past decade, large-scale logging by organized crime groups was responsible for the loss of 1,503 hectares of forest while small-scale operations by communities living near the reserve cut down 554 hectares to build homes.

Another 122 hectares were lost due to droughts and floods.

After peaking between 2005 and 2007, large-scale logging was not a factor last year thanks to government action to protect the forests as well as private donations to assist local communities create jobs and conduct community surveillance, the study found.

In the United States and Canada, where the Monarch begins its 4,500-kilometer trek, the use of herbicides has drastically reduced the number of milkweed that butterfly larvae feed on.

"Neither the government of Canada nor the United States government are doing what they need to do to protect the habitat of the Monarch butterfly," Vidal said.