Since the turn of the century, butterfly populations have plummeted by 22%.

According to research, the population of butterflies in the United States has declined by over a fifth in this century. This includes hundreds of species such as the red admiral, the American lady and the cabbage white.

Researchers said that data from 76,000 surveys of butterflies conducted by different groups, which documented millions of insects representing 554 types, showed a 22% drop in their number from 2000 to 2020 within the contiguous United States. Scientists attributed this decline to habitat loss, pesticides and climate change.

The southwestern region, which includes Arizona, New Mexico and Texas, has seen the largest population decline.

The study documented 342 species of butterflies. Of these, 114 - or about a third - suffered losses. 107 of them were down more than 50%, and 22 by more that 90%. Four butterflies, the Florida white butterfly, Hermes copper butterfly, tailed Orange Butterfly, and Mitchell's Satyr, saw their numbers plummet by over 99%. Nine species, or about 3% of all species, showed increases.

The red admiral has declined by 58%. The cabbage white has fallen by 50%. And the American lady is down by 44%.

The results of this research are quite depressing. "But butterflies can recover if we improve things for the them," said Collin Edwards. He is an ecologist who was formerly at Washington State University and currently works with the Washington State Department of Fish and Wildlife.

Butterflies are known for their rapid life cycles. They produce at least two or three generations per year. Each of these generations lays tons of eggs. Edwards said that butterfly species can respond quickly to our efforts and benefit from them if the world is made more welcoming for them.

Monarch butterflies were included in the study. The study included monarch butterflies. However, because the most clear evidence of their numerical declines is from their wintering grounds in Mexico, and the researchers only used U.S. monitoring information, it was not possible to identify a clear pattern for these butterflies.

In just 20 years, we've lost 1 out of 5 butterflies. If you were to go out and watch butterflies in 2000, you'd see 100 butterflies. In 2020, you'd only see 80. This is a staggering loss in such a short period of time," said Eliza Grames, conservation biologist at Binghamton University.

It is difficult to identify just one stressor that affects butterfly populations. In the Southeast for instance, drought may be a major threat. In the Midwest insecticides are driving the loss of butterfly biodiversity. The story in other regions is less clear. It is more likely that a combination anthropogenic stressors is causing the dramatic declines.

Although reliable data on butterfly populations worldwide is not available, studies conducted in other countries have shown declines that are roughly similar to the U.S. data.

Butterflies are among the most closely monitored insects in the United States. Researchers calculated that there were 650 species of butterflies whose range overlapped with the contiguous United States. At least some monitoring data was available for 554 of these species.

Insects play a crucial role in many ecological processes, and their loss is particularly alarming given the fact that they have been on Earth for over 100 million years.

"Ecologists treat butterflies as a canary for coal mines." Edwards stated that the results of this research suggest there could be a decline in many insect species, for which we do not have reliable data.

The beauty of butterflies inspires me. "They deserve to exist just for the sake that they exist," Grames stated. In terms of ecosystem function butterflies are important pollinators and herbivores, as well as serving prey to insectivores, especially birds.

(source: Reuters)