We have big box stores for pets.
We have semi trucks burning diesel to bring pet food and pet supplies to all parts of the world.
We devote some amount of farm land and livestock to feeding those pets.
It’s interesting when people suggest to reduce global human population but I have never heard anyone suggest to reduce pet populations as a method for combating climate change or for simply reducing resource usage.
The worldwide dog population is estimated to be 900 million.
There are 600 million to 1 billion cats living in the world today.
Most pet food is made from the unwanted scraps/guts left over from processing human food. There are not additional pet food farms - they’re the same farms. Where will the guts go if pets don’t eat it? Cheaper fast food, probably, i.e. more fast food, or waste.
I don’t know that this would reduce anything - just move resources around and probably have other effects that you and I aren’t imagining.
Cats and dogs do require meat to live, unlike humans. Reducing the meat industry will drive up pet food prices, and that may reduce pet ownership. But we better fucking make sure pets are spayed and neutered - doubly so if that ever happens.