Organic farming, also known as ecological farming or biological farming, is an agricultural system that uses fertilizers of organic origin such as compost manure, green manure, and bone meal and places emphasis on techniques such as crop rotation and companion planting. Biological pest control, mixed cropping, and the fostering of insect predators are encouraged. Organic standards are designed to allow the use of naturally-occurring substances while prohibiting or strictly limiting synthetic substances. Organic farming advocates claim advantage in sustainability, self-sufficiency, autonomy and independence, health, food security and safety. Organic farming can be beneficial on biodiversity and environmental protection at local level. However, because organic farming has sometimes lower yields compared to intensive farming, additional agricultural land is needed elsewhere in the world, which means that natural and forest land has to be converted into agricultural land.