Monarch butterflies are finally on the rebound. With the colorful pollinators threatened by everything from pesticides to habitat destruction, the U.S. government pledged $3.2 million to the cause last year. Back in March, a World Wildlife Fund (WWF) Mexico survey found reason for hope, showing a substantial population increase in migration numbers. But the butterflies aren’t in the clear just yet.

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According to University of Chicago professor Marcus Kronforst, in 1996 around one billion monarchs migrated, but in 2013 there were just 35 million. The March WWF Mexico survey revealed the insects were rebounding, with numbers rising to roughly 150 million. More milkweed planted has played a part in the rebound, as has weather that suits the butterflies.

Related: 8 Ways that you can help save monarch butterflies

Natural Resources Defense Council scientist Sylvia Fallon recently told Reuters they are hopeful about curbing butterfly losses. But, she warned,”we must be careful not to declare victory too soon.”

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She was all too right. Researchers from the United States and Mexico utilized drones and satellite images to uncover evidence of illegal logging in Mexico’s Monarch Butterfly Biosphere Reserve, a UNESCO World Heritage site. They published a paper in American Entomologist, in which they report around 25 acres of trees have been chopped down in the last year, destroying important habitat.

Mexico environmental officials arrested 35 loggers in early to mid 2015, but landowners claim logging has been ongoing despite the arrests. The researchers began to grasp the scope of the illegal activity through imagery. Sweet Briar College professor Lincoln Brower, lead author on the paper, told TakePart, “You can’t have huge trucks removing all of this wood without knowledge of what’s going on. It really questions the governance of the reserve.”

Xerces Society for Invertebrate Conservation Endangered Species Program Director Sarina Jepsen said that monarch conservation efforts have centered around the problems of pesticides and planting milkweed, but that we shouldn’t forget butterflies also battle deforestation.

Via TakePart and Reuters

Images via Wikimedia Commons and Luna sin estrellas on Flickr