Monarch butterflies wintering in Mexico could nearly quadruple in number this year thanks to actions taken by the United States, Mexico and Canada to protect the migratory species, authorities said Thursday. After years of sharp decline, the three countries agreed at a summit in February 2014 to form a working group to foster the insect’s survival. More than a year later, the measures “are having an effect,” Mexican Environment Minister Rafael Pacchiano said at a news conference at the Piedra Herrada monarch reserve alongside US Interior Secretary Sally Jewell. Pacchiano said authorities hope the orange and black butterfly will occupy between three and four hectares (7.4 and 9.9 acres) of the mountain forest, located in central Mexico, this season. “This is almost four times (the population) that arrived in the previous season,” Pacchiano said, before a tour of the mountaintop, where hundreds of butterflies were resting or flying around fir trees.

The insect occupied 1.13 hectares of forest in the past season, slightly better than in 2013-2014, when the population hit an all-time low of 0.67 hectares. The goal is to reach six hectares by 2020. This compares to a high of nearly 19 hectares in 1996-1997. Officials measure the size of the population by the area they cover instead of individual numbers.

The falling population has been blamed on illegal logging in their Mexican wintering grounds and the drop in milkweed on which they feed due to the use of pesticides in the United States. Pacchiano said Mexican authorities have launched more operations to combat illegal logging while Jewell said the United States is working on replanting milkweed in three million hectares of land and designating pesticide-free areas.

“Mexico, the US and Canada have many species that don’t know our political borders, that cross the borders freely,” Jewell said. The goal, she said, is “225 million monarch butterflies returning right here to Mexico every year. We believe we can get there by working together and it sounds like we may be on our way, we hope.” The number of butterflies has dropped by 90 percent in the last 25 years.

The butterflies fly 4,000 kilometers (2,500 miles) from Canada to spend the winter in a mountain reserve straddling the states of Mexico and Michoacan. They usually arrive at their nesting ground between late October and early November and head back north in March.