Why America's opossum is an important species as its only native marsupial, and how they are actually very helpful to humans (the first link is audio, the second is text):

http://whyy.org/cms/youbetyourgarden/are-opossums-dangerous-or-natures-helpers-2/

http://www.gardensalive.com/product/did-possums-make-holes-in-the-ground?ai=1378