Insect populations in Brazil suffer significant decline, analysis shows

An analysis of dozens of long-term studies on Brazil’s insect species indicates that they are experiencing significant declines, as seen in many other places on the planet. Many insects, from butterflies to beetles, are becoming less and less abundant, and there are indications that species diversity may also be declining.

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

“In informal conversations with colleagues, people sometimes joke: ‘Wow, that’s good, there’ll be less mosquitoes and flies to get in the way’. But it’s just the opposite — these urban species, which have adapted to the environments we create, will continue around and even multiply. The problem is the other species of insects, the vast majority, very important for the functioning of ecosystems”, explains André Victor Lucci Freitas, co-author of the study and professor at the Department of Animal Biology at Unicamp.

Monitoring the risks that insect species run is much more complicated than carrying out the same monitoring with species of mammals or birds, says Freitas. Among the difficulties are the rapid life cycle — which can last as little as a few weeks or a few months — and large population fluctuations from season to season and year to year.

“I, for example, who work with butterflies, generally only see adults, and it’s more difficult to follow caterpillars, pupae and eggs. It’s not like a herd of elephants, which you can count by flying over individuals or you can use radio transmitters to follow “, compares.

To try to get an idea of ​​the general picture of what is happening with Brazilian insects, the team searched the scientific literature available online, trying to find all the studies that addressed the topic with a follow-up of insect populations of at least four or five. years in duration. They also sent questionnaires to 156 researchers in the field.

With that, they arrived at a total of 75 analyzes on insect population trends in the country, which are part of 45 different studies. The average duration of the surveys is about 20 years, being longer in the case of terrestrial insects (there are also aquatic species, less studied, but very important for the fauna of small watercourses).

Not all Brazilian ecosystems were covered equally in this sample — there is no data for the Pantanal and the caatinga, for example, and the most studied areas are the Atlantic Forest. Even so, most studies on insect abundance (ie, number of individuals of each species) showed a downward trend (in 19 studies). Only five surveys indicated an increase in abundance, while 13 did not indicate any trend.

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

“It is an attempt to understand whether there is a decline or not, and, for the time being, the most solid data showing this is the decrease in abundance”, summarizes the researcher from Unicamp. “I think this is a fact that will provoke a lot of people and that will serve as a stimulus for more systematic studies.”

It is still difficult to be sure what is happening with the trajectory of individual species, but there are already some emblematic cases, such as the beach butterfly (ascanius parides), which has lost much of its habitat in the sandbanks —”Many have become golf courses”, laments Freitas — and the bumblebees Bombus bellicosus and Bombus bahiensis.

Both butterflies and bees are important for flower pollination, but insects perform a number of other crucial functions. “Numerous species of animals feed on caterpillars, for example. And we forget that, before bacteria and fungi, insects such as beetles and termites help to degrade the organic matter of forests and incorporate nutrients into the soil. the effects on the soil and water table can be serious.”