Ohio's butterfly populations have dropped more than a third over the past two decades, scientists have found.
Since 1996, in the study published in the journal, the total populations of the 81 butterfly species have been studied each year. PLOS ONE decreased by an average of 2 percent or a total of 33 percent. In three times as many species, the populations decline compared to the species with positive trends.
In the largest insect monitoring program ever conducted in North America, the team examined the data collected weekly by volunteers in 24,405 butterfly surveys. The citizen scientists monitored 104 locations between April and October from 1996 to 2016. The 116,100 km2 of land across the Midwestern state offers a variety of habitat types, from prairie-like areas to mountains and forests.
Tyson Wepprich, co-author of the study that examined insect populations at Oregon State University, said to Newsweek "There are many concerns over the decline of insects, but very few data We use the best systematic Surveillance dataset for insects in North America to estimate the rate of butterfly frequency change. "
It was found that the monarch butterfly is the only migratory species in Europe to sink, the team found. Forty species showed no significant changes.
Climate change, degradation of habitats and changes in farming practices could explain the decline, the authors wrote.
"Species with more northern spreads and fewer annual generations decreased the fastest," Wepprich said in a statement. This could be because they can not withstand the heat of rising temperatures in Ohio.
The results contribute to the already bleak outlook for insects, as studies of 452 species in the last 40 years suggest a 45 percent decline worldwide
Earlier studies have shown that the migratory monarch in eastern North America has declined by more as 85 percent has declined, while the monarch has fallen by more than 95 percent in western North America. Wepprich said in a statement that some of the rarest butterflies are among the most rapidly falling.
Butterflies provide a useful insight into the threats that insects are generally exposed to, as they are under the same pressure from factors such as climate change and habitat loss. And since most people like butterflies more than other species of insects, it is easier to invite the public to participate in surveillance programs, the authors said.
The decline is similar to that in the UK, the Netherlands and Spain. Wepprich told Newsweek .
"Although these decreases are not as dramatic as others reported recently, this monitoring program has been developed to detect changes in abundance and it shows that the decline of insects in Europe is not only a matter of concern," said he.
Wepprich said Newsweek it is difficult to assess population trends as the numbers of insects vary depending on the season in which they are active or on the flowers that happen to bloom this week in a given year is good or bad for the population.
"We have overcome this problem with statistical methods developed by researchers for other surveillance programs," he said.
"I was surprised that some common species adapted to life in human-dominated habitats such as rural or urban areas are declining," said Wepprich.
"Normally people do not care about pests as the cabbage white shows that the populations of some of the hardest butterfly species may be affected by environmental changes."
Wepprich highlighted the limitations of the work and said the team did not have the Data to find out how other insects in Ohio endure whether the trends would apply to other parts of the world.
Wepprich urged policymakers to think of insects when planning public spaces such as parks, farmland, roadsides, school grounds and other public areas where native flowers and food crops can be planted simultaneously on large areas.
While these actions would have a greater impact than anything individuals can do, Wepperich said he still avoided the use of pesticides in his farms and had replaced grass with indigenous pesticides.
"I enjoy visiting native bees and other pollinators, and especially in urban areas, these small spots can be more beneficial to butterflies and other insects than lawns," he said.