The number of Monarch butterflies has dropped in recent years and experts say that the annual migration is in danger of disappearing as a result.

According to the Associated Press, the number of the beautiful butterflies dropped sharply to its lowest level since record-keeping began in the early ‘90s.

The butterflies now only cover 1.65 acres in a forest near Mexico City, down from 2.93 acres last year, cites a report by the World Wildlife Fund, Mexico's Environment Department and the Natural Protected Areas Commission.

The unique butterflies are known for the yearly migration that brings millions of them to Mexico every winter, the National Geographic notes.

The Monarch’s depend on the forest habitat in central Mexico to survive in the winter. The entire population overwinters there together.

Scientists believe a number of factors may have contributed to the dramatic decline including summer droughts, excessive heat, cold temperatures and unproductive breeding.

Now, the annual cycle is threatened to become non-existent unless conservationist can pinpoint the exact cause of the population drop and work on a possible solution.