consider fruit in the supermarket, that came in plane from another continent. By not buying them, in the short term, there'll be a bit of waste and donations to associations. In the mid/long term supermakets reshape their strategy, stop buying them as well, exporters then reduce their shippings, etc..

same goes for fish/meat productions, if you cut down the consumer stream, the producers will be forced to adapt, takes time sure..

About pets, our planet is overpopulated (at least over-consuming), the fact there are over a billion of pets is already a nonsense, it's like virtually increasing human population by 5-10%, do we really need this?