Idiotic comments like this.

No, I'm serious. None of the things he listed as observing are harmful to the lakes, they are just inconvenient for people.

How exactly, and what from, do they need to be protected?

Also: why the ad hominem? There was nothing idiotic about my simple question.

Stop downvoting and answer the question.

You mean like these?

>over-fished, ... polluted the living hell out of them

Zebra mussels you might be able to claim damage the lake, but the complaints against them are certainly primarily based on nuisance, so I'll exclude them.

  Since zebra mussels became established in Lake Erie, 
  water clarity has increased from 6 inches to 30 feet 
  in some areas. … One drastic impact of the zebra mussel
  invasion is the near extinction of native American 
  unionid clams in Lake St. Clair and in the western 
  basin of Lake Erie.

http://www.glsc.usgs.gov/_files/factsheets/2000-6%20Zebra%20...

Protect the lakes from the sorts of abuses they suffered on a massive scale prior to modern environmental regulations were enforced, and from additional threats like microplastics, fertilizer run-off, sewage, contamination from watercraft, future outbreaks of invasive species transported by ocean-going shipping vessels, large-scale diversion for irrigation or urban water consumption, and a host of other things.

The way you asked it was like "What problems?" when it's obvious that a water-system that vast needs controls or it'll be abused and ruined for everyone.