The combination of threats are contributing to a dramatic decline in the monarch butterfly population.
Monarch butterflies may be facing more threats than initially thought. Many previous studies have associated the decline of the monarch butterfly population with the lack of milkweed, which is the primary food source for monarch larvae, excessive use of pesticides and genetically modified crops. But a new research suggests that problem is not limited to just those few threats.
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Researchers from Cornell University suggest that lack of autumnal nectar sources, weather and habitat fragmentation are also responsible dwindling population of iconic orange and black butterfly.
Monarch butterflies cover a long distance over the United States and Southern Canada before reaching Mexico. Milkweed is only a food source for monarch butterflies in summer but the problem occurs when they begin epic southern migration in autumn.
Each year four generations of monarchs travel over 2,000 miles across North America which begins in early spring when they leave Mexican wintering grounds. Millions of monarchs flow through Texas and Oklahoma and then move to Midwest and Northeast until the start of fall. From roughly late October through February, monarchs live in the forested mountains of Mexico where temperatures are mild enough for their survival and provide them protection from rain and snow.
“Thanks to years of data collected by World Wildlife Fund and citizen scientists across North America, we have pieced together the monarch life cycle to make inferences about what is impacting the butterflies,” said Anurag Agrawal, professor of ecology and evolutionary biology at Cornell University.
“Given the intense interest in monarch conservation, the blame being put on herbicide use and the national dialogue about potentially listing monarchs under the endangered species act, we have to get the science right.”
Due to coordinated conservation efforts, monarch butterflies are now on a rebound and according to a separate research, last December they have covered vast amount of forested areas in Mexico. While that’s positive, the monarchs are still struggling to touch the intended mark.
“The consistent decline at the overwintering sites in Mexico is cause for concern,” said Agrawal.” Nonetheless, the population is six times what it was two years ago, when it was at its all-time low.”