New Scientist puts notes the ecological foot paw print of pets.
The calculations are done in terms of energy per acre, which is something of an apples and oranges comparison. A better calculation would be in terms of pollutants as there are many energy sources with much greater energy densities than the land use given here.
Moving to a CO2e calculation, one finds that beef is really bad - puff and fido should be eating meat in the form of chicken. Of course you should too or, better yet, move to as much of a vegetarian diet as you can. You can't put a dog, cat or ferret on a vegetarian diet though - they aren't made for it.
A huge point is missed. Assuming we manage other areas of carbon emissions, we don't have to drop to zero. Having a pet, for many, is seriously important. Some people have companion animals rather than children. Probably the worst thing you can do to the environment is have children past the number required to sustain population. The emissions produced by an extra American are enormous.