What if all the rats in NYC died tomorrow?

• Rats have lived in North America for at least 250 years.
• But they're technically an invasive species we could do without, according to one expert.
• We asked two rat researchers what would happen if the rodents disappeared overnight.

New York City has been touting its recently implemented method of killing rats. Though it's been very successful in limited capacities, it would take far more to completely eliminate the animals from any city.

It's a far-fetched scenario. Rats are highly adaptable and breed quickly. It would also require a lot of changes to human behavior.

Nonetheless, it's something many city-dwellers have likely dreamed of. After all, rats are widely disliked because of their association with disease and rooting around in garbage, Kaylee Byers, the deputy director of the Canadian Wildlife Health Cooperative in British Columbia, told Insider.

And besides, rats are "an invasive species, and we don't really need them here," in NYC, said biologist Jason Munshi-South, an associate professor at Fordham University.

How did rats get to the US?

"You can find newspaper articles going back decades that mentioned the war on rats in New York City," Munshi-South said. "This has plagued mayors for at least a century."

The Norway rat, also known as the brown rat, is widely dispersed throughout most of the world. It likely arrived in North America in the mid-1700s. From the East Coast, the rats started to spread.

By 1890, The New York Times had reported on a town-wide rat hunt that took place in Iowa.

Today, New York is the third most rat-infested city in the US, according to Orkin. And the bottom line is that we simply don't need them.

Cities don't need rats

Even though rats have been in North America for hundreds of years, they don't play an essential role in maintaining the ecological balance of the cities where they've gained a foothold.

"I don't think rats are an important part of the urban ecosystem," Munshi-South said. "If they were gone, it wouldn't affect us in any negative way."

One report estimated that since 1600, rats introduced to islands have caused between 40% to 60% of all reptile and bird extinctions. With abundant garbage available to them, city rats might not go after wildlife in the same numbers.

However, if all rats in NYC died tomorrow it would still save a lot of animals like birds, coyotes, foxes, and feral cats that die each year from rodenticide, the poison used to kill rats, Munshi-South said.

Byers agreed saying, "One of the big problems is that the poison just doesn't stay in the rats," she said. "It ends up in the animals that feed on the rats, like the predatory birds or other urban wildlife that eat those animals."

As scavengers, rats likely play some role in helping remove garbage from city streets and distributing seeds, Byers said. But Munshi-South countered that and said ants and other animals could fill the role of removing food.

The most positive impact would likely be on people experiencing homelessness or those who live in buildings where rats have invaded.

In her research, "we found that folks experienced a number of mental-health impacts from living alongside rats," Byers said, including stress and anxiety.

"They also can bite people and scratch people," Munshi-South said. "So you don't really want to be in an enclosed space with them or think about them running around your bedroom."

How would a city become rat-free?

Finding new and effective ways to kill rats won't eliminate them from any city, according to both researchers.

"When we're focused on this kill mentality, remove mentality, it often misses the underlying reason why rats are there in the first place," Byers said. "It's the food that we make available to them. It's the areas they can burrow. It's the water. It's our own interaction with our environment."

Better waste management, ensuring buildings are well maintained and inaccessible to rats, and a cultural shift about leaving litter around are some of the barriers the two scientists noted to creating a rat-free city.

"The reality is that in most places, a rat-free city is not going to happen," Byers said. Even if you lived on an island, "you also have to make sure that people don't continue to bring rats onto the island."