All of the orbits. I would rather have a Kessler syndrome around Mars than not.

In the lower orbits, everything will burn up in the atmosphere within five years or so. Orbital decay is very strong under some 400 km.

Also, space is pretty big. Even with a million destroyed satellites out there, the total density of debris would be very low. Imagine spreading debris of a million destroyed cars all over the planet - including the oceans - then walking around and trying to spot a piece. How often would you even see one, much less happen to walk directly over it (=equivalent of a collision)?

The thing is, in orbit you don’t really need to walk around to see the pieces of debris because they come blasting at you from all directions at 7km/s.

Nevertheless, they are still in one place at one time. If anything, my comparison overstates the danger, because Earth's surface is 2D and in space, many of those pieces will fly over or under you.

Your seemingly flippant attitude toward a catastrophic end does not mirror that of the world’s space agencies and leading minds.

They are quite concerned about that particular outcome, Kessler wasn’t just warning us, but predicting an outcome.

NASA sent China a nasty letter the last time China shot down one of its own satellites.

The why is simple. There are launch windows. The more debris in orbit the smaller the windows and shorter their availability.

I believe you overestimate how much orbital debris it would take to ground earthlings for centuries.

I'd actually hope that it leads to fewer, larger satellites that it's practical to go up and repair. At least with a bit of regulatory oversight and some international treaties once this model suddenly becomes feasible with Starship.