When Europeans first settled in Australia they introduced sheep, cattle, horses and crops. In 1856, near Geelong, a few rabbits were released and bred into millions in a few years. These additions were devastating to native plants and animals. Rabbits alter the structure of native plants and contribute to erosion. Myxomatosis and other controls have been introduced with little effect, and as a result rabbits continue to be one of the biggest threats to conservation of native grasslands.