Role of rice paddy fields in our finite planet earth

Abstract

Our ability to control our climatic and financial well-being is being severely challenged, as the IPCC Fourth Evaluation Report of 2007 and the recent global financial crises will testify. At the Summit at Toyo Lake in Hokkaido, Japan in 2008, the delegates gathered to discuss what could be done to tame the global warming phenomenon and the dramatic rise in food and oil prices resulting from globalization. The Japanese Government ratified in June 2007 a strategic plan to make Japan an environmental country for the twenty-first century, as a result of which the Ministry of Environment is committed to the development of what could be called a ‘‘low carbon society’’ or ‘‘natural symbiotic society’’ or ‘‘recycle society’’. The university community has a central role in educating the future leaders of society, especially in environmental science and research so as to enable them to tackle the difficult and complex problems facing us now and in the future. On this point, in this article, I will offer my thoughts on how to deliver practical solutions for many of these problems. In several courses on the environmental science and engineering that I have organized over the years, I have always emphasized lessons learned from natural processes. The most useful source of my inspiration came from the book ‘‘Finite Ecology—Stable and Symbiotic system—’’ by Professor Yasushi Kurihara, which has been re-published as Doujidai-Library194 by Iwanami Publisher. Indeed, more than 30 years ago, when I was a graduate student, Professor Sueshi, my teacher of the ecology class elaborated on the idea of finite ecology as applied to human growth and sustainability. The theory of environmental carrying capacity was central to finite ecology. Since then finite ecology has become my favorite obsession in my teaching and research. Professor Kurihara has experimentally elucidated the intriguing phenomenon that many organisms can survive in a flask where no substrate is supplied. He has named the system of organisms that coexist on subsistent level in this way the co-existence and co-poverty system. Furthermore, Professor Kurihara has proposed other systems, for example, the co-existence and co-prosperity system such as exists in cow rumens, or a system where tension exists always among the constituent members, such as would occur in a space ship. Coming back to the co-poverty system, bacteria first proliferate in a flask under sun light, followed by growth of protozoa. However, as the available substrate is consumed concurrent with a decrease in protozoa, the water surface becomes transparent and changes to green because of chlorella growth by sunlight. After a while, chlorella decrease due to shortage of nutrients, resulting in growth of rotifers in the bulk and of filamentous blue-green algae. As the microorganisms repeat growing and decaying, this ecosystem leads to a steady-state where they stably coexist for a long time. In other words, a sustainable microcosm emerges in the flask. Although a single microorganism decays after substrates are depleted, why can these microorganisms survive in the flask for a long period? Development of such a sustainable microcosm is not created by us; the microorganisms spontaneously design the system in the flask based on light energy and nutrient concentrations in the flask. We can, therefore, learn the basics of material recycling and the energy flow in the natural systems. In addition to the recycle system intertwined with the mechanistically balanced interaction M. Hosomi (&) Department of Chemical Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Nakamichi, Koganei, Tokyo 184-8588, Japan e-mail: hosomi@cc.tuat.ac.jp