Yarrs Flat is on the north western edge of Te Waihora / Lake Ellesmere. The Lake is recognised as being of national and international importance for wetland birds including migratory species. Yarrs Flat Wildlife Management Reserve is on the margins of the Arariri / LII River. It is considered to be of outstanding value for wading birds, high value for waterbirds and swamp birds. Fresh water ponds are used by international waders and numerous wetland birds including Pied Stilt and Banded Dotteral. The Australasian Bittern is known to feed in the area and has been heard booming. Marsh Crake are also present. Animal pests in the reserve are: rats, hedgehogs, mice and mustelids (stoats, ferrets). Possums are also present around the margins of the Arariri / LII.