On a recent trip to the Brockport area to see the new dam restoration, I noticed the slopes had been planted with clover, lots of it.

I thought they said they were planting grass? So why all this clover?

And then I remembered! Many years ago I was a sales rep for a cattle feed company, so I was trained to diagnose and recommend different diets for ruminants (cows, sheep etc). Clover (a legume) mixed into the grass in a field is a good source of nitrogen as it extracts this element from the air and stores it in its roots. As the plant dies off, it leave this element in the ground for grasses to use.
Unfortunately, for some cows, eating too much clover can cause bloat and they can die easily. In a few cases a trochar and cannula punched through the side of the animal into the rumen will relieve the gas.

I doubt we'll be seeing herds of cattle or flocks of sheep on our slopes, so we won't have this to worry about, but no doubt as to why clover has been added to the grass mix, it's to 'fix' nitrogen into the soil to promote grass growth.  Very clever and environmentally sound, in my opinion.

90% of what I saw was clover. Little grass.  Someone mixed up the seed ratio. It doesn't matter much as there is a good mix, which will ultimately lead to a healthy  cover.