Which preposition to use with encroachers

on Occurrences 1%

These encroachers on the waste of nature, says our ally the Russian, if they succeed in their first effort of usurpation, will make war upon us for a title to Kamtschatka.

on Occurrences 1%

The accomplishments which gladden life, As music, drawing, dancing, are Encroachers on our precious time; Their praise or dispraise I forbear.

Which preposition to use with  encroachers