Genetically modified crops engineered to resist herbicides are now more available than conventionally bred resistant varieties.[7] They comprised 83% of the total GM crop area, equating to just under 8% of the arable land worldwide.[7] Approval has been granted to grow crops engineered to be resistant to the herbicides 2,4-dichlorophenoxyacetic acid,[8] dicamba,[9] glufosinate[10] glyphosate,[11] sulfonylurea,[12] oxynil[13] mesotrione[14] and isoxaflutole[15] Most herbicide resistant GM crops have been engineered for glyphosate tolerance, in the USA 93% of soybeans and most of the GM maize grown is glyphosate tolerant.[16]