Organic farming, also known as organic agriculture or ecological farming, or biological farming, is an agricultural system that emphasizes the use of naturally occurring, non-synthetic inputs, such as compost manure, green manure, and bone meal and places emphasis on techniques such as crop rotation, companion planting, and mixed cropping. Biological pest control methods, such as the fostering of insect predators, are also encouraged. Organic agriculture can be defined as "an integrated farming system that strives for sustainability, the enhancement of soil fertility and biological diversity while, with rare exceptions, prohibiting synthetic pesticides, antibiotics, synthetic fertilizers, genetically modified organisms, and growth hormones". It originated early in the 20th century in reaction to rapidly changing farming practices. In 2019, the global area dedicated to certified organic agriculture amounted to 70 million hectares, with more than half of this area being in Australia.