Scientists have been able to successfully genetically modify plants, animals and micro-organisms for a number of years. They do this by manipulating genes to produce genetic changes, which could in theory occur naturally. Supporters of genetically modified (GM) organisms claim that the benefits, such as being able to produce crops that are resistant to disease, could help alleviate world food shortages. Many environmentalists believe that the accidental release of genetically modified organisms into the environment is genetic pollution and they fear that the uncontrolled interbreeding of modified organisms with those occurring naturally will contaminate the environment in unforeseen and possibly dangerous ways. They point out that experiments done by researchers to reassure the public about the safety of GM crops have been carried out under scientifically-controlled conditions which are far-removed from the actual working conditions of food producers.