November 29, 2022
Insect numbers in Brazil have a significant decline - 09/30/2022 - science

Insect numbers in Brazil have a significant decline – 09/30/2022 – science

Analysis of dozens of long-term studies on insect species in Brazil indicates that they are experiencing a significant decline, as has been seen in many other places on the planet. Many insects, from butterflies to beetles, are becoming less abundant, and there are indications that species diversity may be declining as well.

The conclusions have just been published in the specialized journal Biology Letters by a team that includes scientists from unicampGive UFSCar (Federal University of São Carlos) and gives UFRGS (Federal University of Rio Grande do Sul). These are still preliminary data, and there are many gaps in knowledge on the subject of the country, but there are good reasons to consider that the clues available so far are worrisome.

“In casual conversations with colleagues, people sometimes joke: ‘Wow, that’s good, there will be fewer mosquitoes and flies to get in the way.’ But quite the opposite – these urban species, which have adapted to the environments we create, will persist and multiply. The problem is species. Other insects, the vast majority of them, are very important to the functioning of ecosystems,” explains André Victor Lucci Freitas, co-author of the study and professor in the Department of Animal Biology at Unicamp.

Monitoring the risks to insect species is much more complex than doing the same monitoring with mammal or bird species, Freitas says. Among the difficulties are the rapid life cycle – which can last for a few weeks or a few months – and large population fluctuations from season to season and year to year.

“I, for example, who works with butterflies, generally only see adults, and larvae, pupae and eggs are hard to follow. It’s not like a herd of elephants, which you can count on flying over individuals or you can use radio transmitters to follow,” he compares.

To try to get an idea of ​​the overall picture of what’s going on with Brazilian insects, the team searched the scientific literature available online, trying to find all the studies that addressed the topic while at least following insect populations. four or five years. They also sent out questionnaires to 156 researchers in the field.

In doing so, they came up with a total of 75 analyzes of insect population trends in the country, part of 45 different studies. The average duration of surveys is about 20 years, which is longer in the case of terrestrial insects (there are also aquatic species, which are less studied, but are very important for animals of small watercourses).

Not all Brazilian ecosystems were covered equally in this sample – no data on wet land and the Katingafor example, the most studied areas are Atlantic Forest. However, most studies on insect abundance (ie, the number of individuals of each species) showed a downward trend (in 19 studies). Only five surveys indicated an increase in abundance, while 13 surveys indicated no trend.

As for species diversity, 14 studies indicated a decrease, while five indicated increases, but most of the studies analyzed (19) did not indicate a clear trend.

“It is an attempt to understand whether or not there is a decline, and at the moment, the most solid data that shows this is the decrease in abundance,” summarizes the researcher at Unicamp. “I think this is a fact that will excite a lot of people and serve as a catalyst for more systematic studies.”

It is still difficult to ascertain what happens to the trajectory of individual species, but there are indeed some emblematic cases, such as the beach butterfly (Ascanios Paredes), which has lost much of its habitat in the sandbanks — “many of them have become golf courses,” Freitas laments — and bumblebees. Bombus Pelicosos And the Bombus Bahnsis.

Both butterflies and bees are important for pollinating flowers, but insects perform a number of other crucial functions. “Many animal species feed on caterpillars, for example. And we forget that before bacteria and fungi, insects like beetles and termites help degrade forest organic matter and incorporate nutrients into the soil. Effects on soil and water can be dangerous.”