INVASIVE SPECIES: Sheep at N.Y. state preserve cut down on nuisance plants Published: Tuesday, August 26, 2014 Sheep at New York's Rockefeller State Park Preserve are helping to control invasive species and improve soil health. Please subscribe to Greenwire to read the full story. Username: Password: Forgot your access codes? Recover them. Not a subscriber? Sign up for a trial. Ready to subscribe? Click here.