And, this is the official site for the survey in question:
https://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/technical/nra/ceap/na/?cid=nrcs143_014159
Their ‘affiliates’ include (dun dun dun):
“State of the Nation’s Ecosystems offsite link image by The Heinz Center is an important effort to develop indicators for ecological values of what they call grasslands and shrublands.”
I’m worried they might try to designate your land as some “endangered species habitat”.
Tell them, certified mail, that they do NOT have permission to be on your land, and that you will prosecute trespassing to the full extent of the law. Better yet, invest some money in having your attorney send the notice.