Sustainability Repport 2019;
One of the missions of today ’s ecologists is to clarify the mechanism of how groups of organisms survive environmental changes and contribute to sustainable fishery and forestry and the conservation of biodiversity. With researchers of the University of Minnesota, Akira TERUI and other researchers have clarified that the complexity of the branching structure (ecosystem form) of river networks with numerous tributaries contributes to the stable maintenance of groups of organisms. The spatial size of the ecosystem used to be considered the key. This study showed the complexity of a river ecosystem’s form is the key factor supporting the long-term sustainability of groups of organisms based on a mathematical model and The analysis of long-term monitoring data.