By the numbers

Amphibians are a class of invertebrates that includes frogs, toads and salamanders. The creatures are considered to be in precipitous decline. 300 million: Years that amphibians are known to have been on Earth6,300: Approximate known species1,856: Known species that are considered threatened2,469: Species found to be declining in the last two decades168: Species that have gone extinct in the last two decadesSuspected reasons for decline are habitat loss, invasive species, climate warming, chemical contaminants and disease.AmphibaWeb, University of California, Berkeley

Frogs, toads and salamanders are all over the place in the Lowcountry, slinking through wetlands, choraling from trees, even sticking to windows.

WHAT: Tyrone Hayes, subject of the children’s book “The Frog Scientist,” who researched the role of pesticides in the decline of the species, will give a public lecture on the environmental, health, racial and social justice implications of his work.WHEN: 2 p.m. todayWHERE: Sottile Theatre, 44 George St.COST: FreeIF YOU GO

When “frog scientist” Tyrone Hayes was growing up in Columbia, he could stand in Congaree Swamp and hear 30 species of frogs calling at the same time.

So it’s disturbing to realize that amphibians like those raise the most alarm among scientists monitoring the decline of species.

Worldwide, amphibians are disappearing so fast herpetologists say they might be facing mass extinction.

Amphibians are vital to the ecosystem, and to us: They eat insects such as mosquitoes. Their disappearance could very well be a “canary in a coal mine” about increasing environmental threats from man-caused contaminant pollution, habitat loss and invasive species.

Hayes, a University of California, Berkeley, biologist is at the College of Charleston today to talk about his work. A specialist on frogs, he researched the effects on them of the common pesticide atrazine — a project funded by its maker, Syngenta.

He found that the pesticide essentially turned males into females. The company refused the research. Hayes published it, and a nasty public relations battle ensued.

In its wake, Hayes has become an activist against pesticide use, a role model for the conflicts inherent in corporate-funded scientific research and something of a star in the field of biology.

“We can’t fix it. But we can stop it from getting worse,” he said about species decline and the threats.

Amphibians may tend to be more susceptible to contaminants because, unlike mammals, they breathe through their skin, said Allison Welch, College of Charleston herpetology professor; they ingest contaminants easier.

“Amphibians have been recognized as the most threatened group of creatures on the Earth. Frogs do seem to be the most threatened species,” she said. She called Hayes’ research powerful not only for findings but for reinforcing the need to make sure science is an open process.

“It kind of makes you wonder how much else we might not know (about research findings),” she said.

Hayes is continuing his research, now concentrating on whether frogs as a species can adapt to the effects of pesticides and what it means to the future of the species. As an example, the demasculized frogs can reproduce as females, but breed only males, he said.

“Pesticides very likely have a role in amphibian decline. This is a group of animals that has been around since the dinosaurs. I think that says a lot,” he said. “For the first time, a single species is causing that mass extinction.”

And that species is us.

Reach Bo Petersen at 937-5744, @bopete on Twitter or Bo Petersen Reporting on Facebook.