This volume contains the texts of invited papers presented at the Fourth International Conference on Mediterranean Ecosystems (MEDECOS) held in Perth, Western Australia during August 1984. It thus follows three previous meetings, Chile (1971), California (1977) and South Africa (1980). There has been no formal international body to organize these meetings, merely a continuity of purpose provided by the common interests of the scientists concerned in the English-speaking world. Following previous themes on structure, fire and role of nutrients in mediterranean ecosystems, MEDECOS was structured around the theme ''Resilience in Mediterranean Ecosystems''. The invited speakers were requested to deal with particu¿ lar aspects of this subject, and offered papers were encouraged to do so as well. This provided a broad framework for discussions which at the same time highlighted many of the major conservation issues arising from extreme natural events and human-induced disturbances in the med