Monarch butterfly numbers fall on wintering grounds

Monarch butterfly numbers on their wintering grounds were lower in 2020 than in the previous year.
Credit: Charlie Marchant

The number of monarch butterflies landing on their wintering grounds in central Mexico in 2020 has dropped by about 26% from the previous year. Rather than counting individual butterflies, researchers size up the amount of land monarchs occupy when they gather in clusters to winter in pine and fir trees. This past year, illegal logging has taken four times more trees as usual, likely leading to these monarch declines. The butterflies covered 2.1 hectares in 2020 compared to 2.8 hectares the previous year. Experts also believe wind storms, drought and trees dying from beetles or disease may have also played a role in the monarch decline.

Read more in The Guardian.