The Twenty-Ninth Day: Accommodating human needs and numbers to the earth's resources

 In France a riddle is used to instruct schoolchildren in the nature of exponential growth.  The riddle starts with a single leaf in the lily pond, with the number of leaves doubling each day.  The teacher asks when is the pond 1/2 full if it is full on the 30th day, and the answer is "on the 29th day." The world, now with a population of 4 billion, may already be at least 1/2 full.  If doubling of population occurs within the next generation, the "pond" could be entirely full.  A doubling of population would mean that a great majority of countries will be confronted with ecological, economic, and political stresses that may be unmanageable.  Signs of stress on the world's principal biological systems and energy resources indicate that in many places they have already reached their limit and simply cannot withstand a tripling or quadrupling of population pressures.  Population growth multiplies the number of people who are in need of social essentials at the same time it reduces the resources able to satisfy them.  Attention here is focused on understanding the threat of population growth, the dimensions of ecological stresses and the consequences, the impact of population growth on food needs, and economic stresses.  The question remains as to how humankind will accommodate to the earth's natural systems and resources.  Although analysts can define the elements of accommodation and prepare the timetables for making the required changes, only governments have sufficient power to implement them by means of legislation, budgetary and fiscal policies, taxation, and the analytical and educational capacities of government institutions.

Johns Hopkins Bloomberg School of Public Health,Center for Communication Programs,Population Information Program