Habitat for the monarch butterfly has rebounded 69 percent from last year’s dismally low levels, according to the Associated Press and the World Wildlife Fund. Last year was the lowest year on record for the species – a poor sign of the species’ condition.
Each autumn the butterflies make their 3000-mile annual migration from Canada through the U.S. to Mexico, traveling across the sky as massive orange and black clouds. The monarchs travel to their ancestral breeding grounds in the temperate volcanic mountains just outside of Mexico City – a destination unknown until 1977. Even though no creature lives to make the round trip, the butterflies return to the same fir and pine forests as their ancestors had, covering every branch of the trees, often forming beautiful chandelier shapes.
Record keeping only began in 1993, but scientists have collected enough data on the delicate species to know when the butterflies are in danger.
In 1996, scientists saw monarchs wintering across 44.5 acres (18 hectares) of the breeding grounds. Last year was a record low for monarch butterflies, with the species only found within a tiny 1.66 acres (0.67 hectares) of the grounds. Scientists were glad to see 2.79 acres (1.13 hectares) covered with monarchs this year – a significant 69 percent rebound from last year and a hopeful sign of the species’ recovery.
Omar Vidal, head of the World Wildlife Fund in Mexico, said that this year is great news for the species’ welfare. He continued skeptically, “But let’s be crystal clear, 1.13 hectares is very, very low, and it is still the second-smallest forest surface occupied by this butterfly in 22 years of monitoring.”
In discussing the monarchs’ population, Sweet Briar College entomologist Lincoln Brower explained that if only an area below 4.1 acres (2 hectares) is occupied, “they will remain in the danger category and I will continue to be concerned.” According to Brower, a population covering 9 to 12 acres (4 to 5 hectares) would signify a promising recovery.
While last year was the smallest the monarch population has shrunken in recorded history, it had not been the first time the population took a dive.
In 2001, extreme weather including heavy rains and large cold fronts led to the death of millions of the butterflies. While scientists predicted that population numbers would be significantly lower in 2002, twice as many miraculously returned to the breeding grounds the following year.
Also, in 2004 the monarch population took a drastic decline before bouncing back the next winter. This is thought to have been due to excessive pollution, poor weather, and deforestation within essential monarch habitat.
Despite these various population rebounds, there has been a steady and threatening decline in monarch population over the past 22 years. Even with each rebound, the species has not returned in full.
While the species is not actually in danger of extinction – experts fear that the migration might be disrupted as fewer monarchs successfully make the journey. The migration and its route are inherited traits, while it still remains an enigma to scientists how these traits are actually passed on. One theory suggests that the monarchs release a chemical throughout their migration route that provides a trail for future generations to follow. With a decline in population this chemical trace may lose its ability to lead descendants to the breeding grounds– a serious threat to the customary migration.
Monarchs are threatened most by extreme weather and drought, a concern that is increasing with global climate change. Illegal logging in the mountains outside of Mexico City destroys the habitat that safeguards the butterflies’ breeding grounds, although Mexican authorities have largely halted these activities.
One of the biggest threats to the vitality of the species’ population happens in the United States. The monarchs’ main food source – milkweed – has almost entirely been replaced by pesticide-resistant crops throughout the nation, leaving little food for the delicate butterflies. As we look forward, saving this food source could be the biggest hope for restoring the species’ population.
Do you want to see this amazing migration? Visit Mexico’s lush green mountains to experience the kingdom of the monarchs with Nat Hab and WWF!