The Decline of Butterfly Populations

Butterflies, celebrated for their vibrant colors and essential role in pollination, are disappearing from the U.S. at an alarming rate. A recent comprehensive study published in the journal Science highlights that 22% of butterfly populations have vanished between 2000 and 2020.

This significant decline serves as a critical alert regarding the future of these beloved insects. Dr. Eliza Grames, an assistant professor of biological sciences at Binghamton University and a co-author of the study, emphasized the urgency of the situation: “Losing one out of every five butterflies over 20 years should be a big wake-up call to people. These declines are not stopping.”

Research Findings

In contrast to previous studies that were often localized or specific to certain species, this extensive research analyzed data encompassing over 12.6 million individual butterflies across 342 species, compiled from 76,000 surveys in 35 monitoring programs nationwide. Funded by the U.S. Geological Survey, this is the first study to integrate such a comprehensive dataset.

The findings are alarming: a third of butterfly species examined have experienced significant population losses within the last 20 years. Out of the 342 species, 107 have seen their populations decline by more than 50%, with 22 species suffering declines exceeding 90%. Conversely, only 3% of the species have shown an increase in their populations.

The Case of the Monarch Butterfly

Among the most affected species is the iconic monarch butterfly. The U.S. Fish and Wildlife Service proposed listing the monarch under the Endangered Species Act in December 2024, citing an 80% decline in its eastern population and a staggering 95% decline in the western population since the 1980s. Additionally, the International Union for the Conservation of Nature designated the monarch as endangered in 2022.

The Broader Insect Crisis

The decline in butterfly populations is part of a larger global decline in insect populations, with estimates suggesting an annual decline of 1-2%. This loss is concerning because butterflies play a vital role in ecosystems, particularly in pollinating flowers, crops, and other plants. Their decline could disrupt plant reproduction and ultimately threaten ecosystem health.

Causes of Decline

According to the study, several factors are driving the decline of butterfly populations, including:

• Habitat loss
• Climate change
• Pesticide use

Climate change is particularly detrimental, as it can disrupt breeding cycles, diminish food sources, and stress habitats. The use of insecticides has been identified as a primary contributor to butterfly population declines. The authors suggest that policy interventions, such as restricting harmful insecticides and promoting integrated pest management, could help mitigate these impacts.

What Can Be Done?

Despite the ongoing decline, individuals can play a role in fostering butterfly recovery. Dr. Grames notes, “One of the really positive messages about insect conservation is that the things we do in our own backyards actually make a difference.” She advocates for:

• Allowing portions of yards to grow wild with native plants
• Reducing pesticide usage
• Creating insect-friendly habitats, such as brush piles
• Planting native flowers that support pollinator populations

On a community and global scale, experts emphasize the importance of conservation efforts, habitat preservation, and strategies for climate adaptation to protect vulnerable species and ensure butterfly populations remain resilient amid ongoing environmental challenges.