To answer your question, the firearms are needed for protection from both wildlife and people, but much more so people. It's useful to have a rifle to put down a cow that's been hit by a vehicle and/or broken a leg or something.

However, I live in an area where stumbling upon foreign cartel marijuana grows is relatively common. They are known to aggressively defend them with firearms which are not legal to own in the jurisdiction they're in. It's also not uncommon for a truck full of guys intent on committing armed robbery to roll up onto a client's property.

An AR-15 would be an ideal defensive weapon for that use-case.