It is real grass (or recently laid turf). This doesn't look like a normal carpark, it may be used for special functions (like conferences in the lecture theatre) but I really don't know. The wall you see running along the left side of the photo is the main Northerly perimeter wall (that used to have the old reptile house behind it), and the Main entrance is just to the left of the photo, but out of shot. The multistorey carpark is to the right of this photo.
I took this shot because it used to be the "bottom carpark" - before the multistorey was built - when you drove into the carpark, this lower area was close to the main gate and you could park your car under the trees.