Whilst farming practices (as opposed to hunting and gathering) have existed for eons, by the twentieth century these had evolved in many parts of the world into large-scale commercial enterprises. Contemporary practices incorporate crop and animal specialisation, uniform monocultures, mechanisation of labour, consolidation of farms and market concentration, the application of chemical inputs, and the use of genetically modified crops. Evolving cultural values and political sensibilities mean that modern agriculture is fraught with conflict, with animal welfare and climate change being most prominent. Agriculture broadly and farmers individually can be pre-eminent in environmental harm and crime. Farmers are also victims of the effects of climate change and in some instances are at the forefront of conservation efforts.