New studies reveal that warmer fall temperatures have a damaging effect on monarch migration and overall fitness. As a result, they face catastrophic repercussions for their species. Monarch butterflies undertake one of the most incredible migrations on our planet—3,000 miles from the United States and Canada to Mexico or Southern California. These vital creatures are increasingly threatened by climate change. The review underscores serious shortcomings across the conservation space, pointing to an urgent need to target and effectively tackle drivers of their decline.
Usually, monarch butterflies have a lifespan of only around a month in the summer. Their last summer generation of monarchs lives an exceptionally long life of close to eight months. This astonishing longevity is what enables them to survive the winter. Sadly, this incredible adaptation is being undermined by changing climatic patterns which affect their ability to successfully both migrate and breed.
Declining Populations and Habitat Loss
Unfortunately, as anyone who’s followed the plight of the monarch butterfly knows, these overwintering populations have experienced a dramatic decline in recent decades. Habitat loss is critically important in driving this downtrend. Climate change and pollution, urban development and agricultural runoff are poisoning or otherwise reducing the availability of these essential life-giving resources. Milkweed, the only food for monarch caterpillars, has been wiped out across the U.S. at an alarming rate. This dramatic loss in milkweed habitat is one of the main culprits behind the population collapse for our iconic monarch butterflies.
Beyond habitat loss, one of the biggest threats facing these butterflies is a parasite called Ophryocystis elektroscirrha (OE). This parasite does a considerable number on the butterflies. Ultimately, this makes it more difficult for them to finish their migration, causing increased mortality among those infected. As researchers strive to understand the full extent of these threats, the need for effective conservation strategies becomes ever more pressing.
The Impact of Temperature on Migration
In a new laboratory study, scientists kept 499 wild-caught monarch butterflies in conditions mimicking “warm” migratory temperatures. They examined the impact of over a 30-day exposure to “cold” temperatures. The results indicated a concerning trend: monarch butterflies that experienced warm migratory conditions exhibited a 28% greater risk of mortality compared to those in cooler environments. This discovery highlights just how important temperature is to the overwintering survival of monarchs.
Monarch butterflies enter a special stage known as diapause when they migrate. This tactic allows them to put off breeding and focus their energy on making it to their wintering grounds. Increasing fall heat disrupts this instinctive cycle, messing with everything from their migration routes to their physical well-being. Climate change is intensifying storms and altering weather patterns. When considering conservation strategies, it’s important to know what effects these changes have on both summer and winter monarch populations.
The Future of Monarch Butterflies
Climate change repercussions go well beyond just increasing predicted mortality. It could drastically change migratory pathways for monarch butterflies. As fall temperatures increasingly start to warm, the natural cues that signal it’s time to migrate can become inconsistent or not reliable. This can result in not only earlier departures, but timing out of sync with seasonal changes in their habitats.
Conservationists remind us that the best way to overcome these challenges is with steadfast commitment to habitat restoration and protection. By making more milkweeds available, we can make strides toward sustaining healthier monarch populations. Further, protecting important migratory corridors will help shield them from rapidly encroaching environmental change. Moreover, as highlighted in the study, public awareness campaigns play a critical role in building community support for conservation efforts.