Ohio butterflies die as monarchs, rare species, decline of one-third in two decades

Scientists have revealed that butterfly populations in Ohio have declined by more than a third over the past two decades.

Every year since 1996, all the populations of the 81 species of butterflies examined in the study published in the newspaper PLOS ONE dropped by an average of 2%, or 33% in total. Three times more species see their populations decrease compared to those whose trends are positive.

As part of the largest insect monitoring program ever conducted in North America, the team reviewed weekly volunteer data from 24,405 butterfly surveys. Citizen scientists monitored 104 sites from April to October, from 1996 to 2016. The 116,100 km of² An expanse of land on which the Midwestern state expands provides a variety of habitat types, ranging from grassland-type areas to mountains and forest.

Tyson Wepprich, a co-author of the study that studies the insect populations of Oregon State University, said Newsweek: "There is a lot of concern about the decline of insects, but very little data apart from some long-term monitoring programs in Europe.We use the best systematic insect monitoring dataset in North America to estimate the rate of change of abundance of butterflies. "

The team discovered that the monarch butterfly was the only migratory species in decline. Forty species have seen no significant change.

The authors wrote that climate change, as well as habitat degradation and changes in production methods, may explain this decline.

"Species with more northern distributions and fewer annual generations have experienced the fastest decline," Wepprich said in a statement. This may be because they can not withstand the heat as temperatures rise in Ohio.

The results reinforce the already gloomy outlook for insects, as previous research on 452 species suggests that numbers have fallen by 45% globally over the past 40 years.

Previous studies have shown that the eastern North American migratory monarch had decreased by more than 85%, while that of the North American monarch had declined by more than 95%. Wepprich said in a statement that some of the rarest butterflies are among those who fall sharply.

Butterflies provide a useful overview of the threats facing insects in general, as they face the same pressures due to factors such as climate change and habitat loss. And since most people love butterflies more than other insect species, it's easier to ask the public to participate in surveillance programs, the authors said.

The decline is similar to that observed in the United Kingdom, the Netherlands and Spain, said Wepprich. Newsweek.

"Although these declines are not as drastic as others recently reported, this monitoring program is designed to detect changes in abundance and shows that declines in insects are not just a source of concern in Europe, "he said.

Wepprich said Newsweek It is difficult to estimate population trends as the number of insects fluctuates depending on the season of activity, flowers blooming this week or favorable or unfavorable weather conditions. given year for the population.

"We have overcome this problem by using statistical methods developed by researchers for other surveillance programs," he said.

"I've been surprised by the decline of some common species suitable for living in human-dominated habitats, such as agricultural or urban areas," Wepprich said.

"Usually pests, like white cabbage, do not worry, but we think this shows that populations of some of the most resistant butterfly species could be affected by environmental changes."

Highlighting the limitations of the job, Mr. Wepprich said the team did not have the data needed to determine the status of other insects in Ohio and determine if trends would apply to them. other regions of the world.

Wepprich urged decision-makers to think of insects when they plan public spaces such as parks, farmland, roadsides, school yards and other public spaces where planting native flowers and food plants can be carried out on large areas at a time.

Although these actions have a greater impact than anything that individuals can do, Wepperich said that he always avoided using pesticides in his garden and had replaced some of the grass by native plants.

"I like to see native bees and other pollinators come in. Especially in urban areas, these little spots can benefit more butterflies and other insects than lawns," he said. declared.