I think it is the easement too. I think also ANY TIME during those 18 years they could have blockaded the property or at least sent a letter advising them they were not to tresspass.
ANYTHING TO SAY the tresspass was known and not welcome.
People forget the key to adverse possession is INACTION by the owner.
” McLean and Stevens were unable to provide any photographs of any paths existing prior to one year ago, even though they claimed these paths were obvious for more than 18 years.”