After The United Nations Conference On The Human Environment in Stockholm of 1972, people finally realized that Earth is a closed system and that mankind cannot continue to grow (proliferate) forever. From the beginning of the 18th century till the end of the 21st, mankind has experienced massive growth, the largest proliferation in history and something which will probably never happen again. Various methods of estimation and logistic curves which roughly describe the population change in a closed system have been used to predict that the saturation point for the population on Earth is around 10 billion.

从1972年的斯德哥尔摩人类环境会议以来，人类切实地了解到地球是一个封闭的体系，人类不会无限繁殖。从18世纪初到21世纪末，人类在近代文明史上描绘出有史以来最大的、恐怕也是历史上唯一的一次大繁殖。利用各种推算法和大略记述着封闭体系的人口变化的逻辑曲线等而预想出来的地球的饱和人口是100亿人左右。

Professor Tambo advocated a new post modern paradigm as early as 1970’s for the 21st century and assumed that at least half century might be needed to materialize his concept in real city plan.  The new paradigm of water system for the 21st century post modern world that he proposed is that the urban/regional water metabolic system of the next era will be designed to supply optimum quality of water for specific usages with necessary amount for the use through appropriate integrated systematic use and recycle of water resources at minimum cost (energy-consumption rate) with the technological and managerial goal that the cities and regions involved in water usage and drainage (urban water metabolism ) should take direct and proper responsibilities over the water environment.  He suggested an importance to graduate from the rather rude conventional/modern water system to supply top quality water en bloc for every purpose (modern water supply system) and then to dispose the used water again en bloc as “sewage” (modern sewage work system).  He thought that the conventional modern water and wastewater systems are possible to sustain only when ample regional water resources exist.  The above concept became the basis of the Singapore Green Plan 2012.