or call the cops. I'd think the fire department might have a problem with that too. I know they don't like vehicles parked so tight to buildings that their guys can't squeeze by.

Waste of time for the most part & have you seen how cops handle even simple problems nowadays?. The tenant could end up dead because of such a call.
County if you want to call anyone but maybe figure it is hard to recycle with Covid limitations at the recycle centers.

Sounds like the start of a hoarding situation. NIP IT IN THE BUD.

And the homeless rely on the proceeds a great deal. It does stop the littering problem.

But it is nearly impossible to recycle nowadays. At least in my area.

It was a chore before but I got it done on a semi monthly basis. And now I have about 5 months worth waiting because the lines are so long to get your deposits back.
This is almost $200.00 worth for my family.

I'd suggest Y'all lighten up for heavens sake.

And, of course, once they have found a nice refuge those rodents chew everything and try to eat everything.

As noted by others a fire hazard both as something which burns readily and something which will get in the way of firefighters if something else is burning and they need access.

And it will trap moisture against the side of the building. Depending on the climate and construction materials/techniques, this could facilitate mold/mildew/fungi/moss or termites/other insects damaging the building.

The landlord should care but you would know best of they actually will or not. Also you're in the best position to judge whether or not it is worth it to try to get them involved -- depends on the various personalities, etc.

And how long does the tenant say they be removed?

If they render cash when recycled, and they actually will be recycled... I'd leave them be, some folks aren't willing to talk about money issues and this could just be one way the other tenant has to gain a little pocket change.