Butterflies disappearing from Earth at ‘alarming’ rate: study

By Stephen Beech

Butterflies are disappearing at an "alarming" rate, warns new research.

More than one in five butterflies in the United States has disappeared since 2000, say scientists.

And the largest-ever analysis of its kind, involving more than 12.6 million butterflies across 342 species, raises the possibility of a world without them.

Researchers looked at data from 76,000 surveys of the colorful insects that play a vital role in pollination.

Their findings, published in the journal Science, showed that butterfly abundance fell by 22% between 2000 and 2020 in the US.

The results also revealed that 13 times as many species declined as increased – with 107 species losing more than half their populations.

Study co-author Professor Elise Zipkin, of Michigan State University (MSU), said: “Action must be taken.

“To lose 22% of butterflies across the continental United States in just two decades is distressing and shows a clear need for broad-scale conservation interventions.”

Co-author Professor Nick Haddad, also of MSU, said: “My neighbors notice it.

“Unprompted, they’ll say, ‘I’m seeing fewer butterflies in my garden, is that real?’ My neighbors are right. And it’s so shocking.”

Butterfly populations dropped an average of 1.3% annually across the US, except for the Pacific Northwest.

But the apparent 10% increase in overall abundance in the Pacific Northwest over the 20-year study period was credited largely to the California tortoiseshell butterfly, which was enjoying a population boom not expected to be sustained.

Study lead author Dr. Collin Edwards said: "This is the definitive study of butterflies in the US.

“For those who were not already aware of insect declines, this should be a wake-up call.

"We urgently need both local- and national-scale conservation efforts to support butterflies and other insects.

"We have never had as clear and compelling a picture of butterfly declines as we do now.”

The research team pointed out that butterflies play important roles in cycling nutrients and are a "significant" food source for other organisms such as birds.

Over the last 50 years, North America has lost nearly three billion birds, a decline at almost identical rates of the butterflies.

Zipkin said: “People depend on plants, microbes, and animals for the air we breathe, the water we drink, and the food we eat.

"Yet, we are losing species at rates that rival the major mass extinction events on our planet,

“The US plays an important role in setting policies and creating laws that conserve and protect biodiversity from local to global scales.

"Our leaders and the federal government, in particular, are responsible for making sure future generations have the necessary resources to thrive.”

The team warned that widespread use of insecticides is a key factor in the decline of butterfly numbers.

However, there are different drivers across different regions of the US. For example, in the Southwest, there are concerns about drought, whereas in the Northeast, it’s more about climate.

Haddad said: “Prophylactic and near-universal application of insecticides harms butterflies and other beneficial insects, with no proven benefit to crop yield.

“What is applied as ‘insurance’ is extracting a great debt to agroecosystems.

"The good news is that the widespread application of insecticides can be reversed, and butterflies and other pollinators will recover.”

The research team hopes the study could help drive important conservation efforts, such as prioritizing species for the International Union for Conservation of Nature (IUCN) Red List of Threatened Species or Endangered Species Act protection.

Study co-author Dr. Eliza Grames, an Assistant Professor of biological sciences at Binghamton University, New York, added: “Insects are declining at rates of about 1-2% per year, which has come out across several studies.

“This was another study finding a super similar rate of decline, which really adds evidence to the growing picture of insect declines globally.”