The need for increased crop yields has led to growing interest and research in agricultural intensification, which has a myriad of extensive system, the intensive system requires considerable skills, efficient management and a great deal of animal feed. Extensive Farming Systems and the Ecological Environment. David Tilman, Kenneth G. Cassman, Pamela A. Matson, Rosamond Naylor & Stephen Polasky. Introduction The aims of this review are, therefore, to 1) develop a more complete understanding of