"now have biological contaminants, there's bugs and fungus"

Dude, we have rats running around, pigeons nesting and pooping, what biological contaminants?

Just because biological contaminants exist doesn't mean adding more creates more issues. More trees also means more rats and pigeons. What's your argument? That just because we already have a bad thing doesn't mean that a similar bad thing isn't bad? That doesn't make much sense and is a pretty lazy argument.

Either way, rats and pigeons feed on garbage, they dont eat oak trees.

We need to have less takeaway left on the street and garbage bins that are cleaned up on time.

How much irrigation that is needed very much depends on where you are and what kind of tree. After the first few years it take to settle, trees have deep roots and rarely need watering.

And I have never heard of trees contribution negatively to "biological contaminants", whatever that means. Rather, trees contribute to a cleaner and healthier environment.