USA - First they say have no children, now no pets! According to a study out Monday on global climate change, your dog (or your cat) is probably killing the environment, and if you want to stem the tide of global warming, it's time to say "good-bye" to Fido and Fluffy. Researchers at the University of Sydney in Australia claim that those 163 million pets have a detrimental impact on the environment, from the food they consume to the waste they produce. Alternatively, the researchers recommend having your pets go vegetarian, something that's not recommended by veterinarians or animal health and welfare experts who concede that having some type of meat-based protein is best for your four-legged friends — particularly those whose ancestors were carnivorous.