WORCESTER - The fur is flying over free-ranging cats and their impact on wildlife and public health. Some area researchers are calling for more calm, comprehensive debate.

At issue is the validity of evidence that cats pose a significant threat, and the ethical ramifications of public policy to address cats and biodiversity, which has gone as far as mass extermination plans for feral cats, according to an essay published last month in the journal Conservation Biology.

“A moral panic over cats” is authored by Clark University research scientist William S. Lynn, Tufts University veterinarian and public health researcher Joann Lindenmayer and four other scientists and ethicists from the United States and Australia.

“Cats get essentially profiled as an enemy of the people,” Mr. Lynn said in an interview.

He pointed to policies enacted in places such as Australia, which decided in 2015 to try to kill 2 million cats by 2020 out of concern for native wildlife.

Lethal policies are “in people’s minds” in the United States as well, Mr. Lynn said.

The American Bird Conservancy launched a Cats Indoors campaign, claiming on its website that cats kill more than 2.4 billion birds in the U.S. each year. The organization opposes nonlethal trap, neuter and return (sometimes called release) programs to limit the feral cat population.

The authors raised particular concern about a letter published in Conservation Biology in 2018, “Merchants of doubt in the free-ranging cat conflict,” by Peter P. Marra of Georgetown University, who formerly was the director of the Smithsonian Migratory Bird Center, and Scott R. Loss of Oklahoma State University.

Mr. Marra and Mr. Loss argued in their 2018 letter that free-ranging cats threaten humans as hosts of diseases such as toxoplasmosis and rabies, cause “tremendous wildlife mortality,” have contributed to at least 63 species extinctions, and negatively affect wildlife populations worldwide.

“Conservation professionals generally view free-ranging cats as invasive species, whereas TNR (trap, neuter and return) advocates view them as individuals with a right to roam free,” Mr. Marra and Mr. Loss wrote.

The letter writers suggested that those who raised questions about the science and ethics behind cat-removal policies were duplicating “past approaches of cigarette and climate-change fact fighters,” essentially calling their critics special-interest science deniers who seek to misinform the public.

“This is the hottest debate I’ve ever worked on,” Mr. Lynn said.

The response on Twitter has gotten emotional and vulgar at times. A Twitter screenshot sent by Mr. Lynn showed Mr. Marra referring to cats as "one of the most destructive invasive species on earth."

But he said he’s also heard from conservationists who agreed that discussions about free-ranging cats and wildlife need to be more thoughtful than the push to eliminate cats.

Mr. Lynn said the team wrote the essay to clarify the science, the ethics and the public policy implications.

He said, “We can’t kill our way back to biodiversity.”

Are cats a major problem?

“No one really knows,” Mr. Lynn said.

In certain circumstances they can suppress some species, just like any predator, he said. In contained island ecologies, they can be a threat to biodiversity.

But in general, cats often suppress other wildlife like rats and mice, which cause more harm as disease carriers.

He said in urban areas, the potential for damage to biodiversity was very small.

“It’s always ecologically complex,” he said.

Mr. Lynn acknowledged that more could be done to keep cats indoors, particularly during the night, when they’re likely to hunt, and in the spring fledgling season.

Catios, cat enclosures that can be added to a house, are an option for cats to get a taste of the outdoors but still be kept from roaming free.

Cat colonies shouldn’t be located by wildlife sanctuaries, he said.

And there should be stricter spaying and neutering of cats. He called trap, neuter and return programs a good step, but not the total solution.

Mr. Lynn and his colleagues argued that discussions about the ecological and public health issues needed to grapple with the intrinsic value of all animals and how we think about cats as members of our society.

“I think it’s been overblown, as far as birds and biodiversity go,” Dr. Lindenmayer said.

She noted that any species carries diseases, including humans. For example, Ebola, one of the world’s deadliest recent epidemics, is transmitted by people.

Access to veterinary care and responsible cat ownership, including keeping cats inside, play a role in how big a threat cats present, she said.

According to the American Veterinary Medical Association, 57% of households in the U.S. own a pet. Dogs are No. 1, in 38% of households, while 25% of households own cats.

Human activity and human neglect are mostly responsible for the damage attributed to cats, according to Dr. Lindenmayer.

Still, she said, she knows wildlife veterinarians who are “simply closed to the idea that maybe we should think again before we go killing all cats.”

She said, “The evidence may not be there to take that kind of slash-and-burn approach.”

Experience in countries where dogs have been targeted for elimination, by police with shotguns or by poisoning, which Dr. Lindenmayer witnessed as a Peace Corps volunteer in Southeast Asia and Africa, haven’t worked. Other dogs moved in to replace those eliminated.

“There’s a ton of research on how ineffective this is,” Dr. Lindenmayer said. “It’s appalling.”

“It’s not decimating the (wildlife) population,” said Melanie DuLac, cat adoption and foster care coordinator at Worcester Animal Rescue League. “It’s basically survival of the fittest.”

Ms. DuLac said that the shelter receives mostly strays brought in by the public, by animal control officers or from area animal hospitals.

Despite what critics of trap, neuter and return programs say, according to Ms. DuLac, national studies have shown that they can be very successful in reducing free-ranging cat populations. In Waco, Texas, for example, regional coordination of animal control officers, volunteer trappers and free spay/neuter clinics have gotten the problem under control.