Thousands of striking orange and black monarch butterflies began arriving to their winter home in central Mexico on Saturday (November 26) in their annual migration. The 4,800-kilometre mass migration of monarch butterflies in North America is one of the insect world’s fantastic feats, with millions embarking on the arduous journey from as far north as Canada down into Mexico and the California coast each autumn. The number of migrating monarchs has plummeted in recent years.
Experts say that while an estimated one billion monarch butterflies migrated to Mexico in 1996, that number stood at about 35 million last year. Threats to them include habitat loss due to human activities, pesticides and climate change, the experts say. Scientists at the Ecosystems Research Centre at the National Autonomous University of Mexico in Morelia, have in recent years developed an organic fertilizer that is being spread throughout Mexico’s forests to protect the butterflies. The National Commission for Protected Natural Areas has also stepped up monitoring across woodland areas near the U.S. border. Population losses suffered by the charismatic butterfly stem from destruction of milkweed plants they depend on to lay their eggs and nourish hatching larvae. The plant’s decline is tied to factors such as increased cultivation of crops genetically engineered to withstand herbicides that kill native vegetation like milkweed, conservationists say.