My brain spent about 2.5 seconds wondering how the hell you spay or neuter a rat before giving up.

I'm sure I read a [news] story about this many years ago and have wondered what became of it, perhaps these guys?

https://senestech.com/contrapest/

It can be done to drosophila, as alluded to in https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3197105/

It's expensive and risky, and it can be hard to find a specialist vet. I kept pet rats once, and it was easier to just separate the males and females from each other.

I know yours is a joke comment, but without the dogs eating the food (the garbage), some other animal is going to eat it instead. I predict an explosion of rats in another decade.

Not really. Dogs often topple over garbage bin, and spill content on streets. Some countries use garbage bags, dogs break those. Without dogs, there is a good chance garbage just stays in bins, and gets actually collected!

Rats are quite good at climbing and chewing - they are very able to get into garbage cans, unless they are metal and latched.