Scientists like Brown, however, aren't advocating that domesticated animals go the way of the eight-track tape.
"Any claims on the Earth's resources, whether it's having pets or having children, we need to think about. It doesn't necessarily mean getting rid of your pet now. But when the pet dies, as they eventually do, you might want to think about whether you replace it or not," he said.
"I don't think there's any way of saying how many pets somebody should have or a country should have," Brown added. "But it is useful to think about the environmental demands that pets make in the same way that people do."
Pets are an "irreplaceable feature of our lives and our culture," Pacelle said. "And there's no stepping back."