1. The public debate about genetically modified organisms has concentrated largely on concerns about food safety and potential risks to the environment. In both cases there appears to be an assumption that existing crops and animals are safe. I discuss the experience we have to date from traditional methods and conclude that most concerns about environmental harm are more relevant to existing crops.2. The flow of genes among species, and even within different genera, is discussed with due attention being paid to the need for inherited genes to confer a selective advantage on hosts.3. A reason why so many people are critical of intensive agriculture and biotechnology is that virtually all changes in agricultural practice have an adverse impact on wildlife, particularly when such change leads to increased intensification. The problem of deciding how to manage agriculture to ensure that we maintain or enhance species diversity of wild plants and animals is discussed against the background that most of the UK environment is the result of human intervention.4. Nature and dense human populations cannot coexist without the former suffering. Our objective should be to develop and exploit our understanding of ecology to provide the information required to enable us to develop a far more enlightened future for agriculture and wildlife.