bacteria. While the scientific community generally acknowledges the possibility of these risks, the scenarios are hard to quantify, particularly in a Risk-Cost Benefit Analysis (RCBA) model commonly used in public policy. Proponents of the technology dispute many of these findings or the significance of the risk factors. They generally contend that the GE strains have no further evolutionary advantage than any other new strain introduced into a local ecosystem and that they behave in the same way. They also cite less need for pesticides than conventional non-organic crops. Opponents, by contrast, adhere to the precautionary principle, which advocates waiting until further study is done and puts the burden of proof on the producer to prove that their productive activities are no threat to the environment or human health before continuing. The precautionary principle has become the foundation of environmental policy for the EU. Causes The promulgation of agricultural biotechnology follows a trajectory that began in what is commonly referred to as the "green revolution". In the twentieth century, industrial methods were increasingly applied to agriculture for the mass production of monocultures, large tracts of land used for the production of single high yield crops with the use of fertilizers and pesticides. The actual physical problem GEOs seek to address, most commonly, is the destruction of crops from pests. The gradual shift towards monoculture has increased the frequency and severity of pest invasion and infestation because of the lack of agricultural diversity. Many pests that threaten different crops are natural predators to each other, which helps to offset their impacts. When many miles of the same crop are planted, however, it leaves the local habitat more vulnerable to the threat of single pest. GEOs have brought short-term benefits in the control of pests by having genetically programmed immunities to the pesticides that are produced to be used along with them, such as the well-known post-emergence herbicide Roundup produced by Monsanto. The primary forces that are driving the production of GEOs, however, are social and economic. GEOs are the latest development in the drive to produce higher yields with less inputs, according to the profit maximization model. Proponents of the technology see it as an answer to growing food shortages in the face of rising global population. They also cite potential benefits, such as the creation of more healthy strains of produce, aquaculture or livestock, with higher nutrient content and less fat.