"Neglect in protecting our heritage of natural resources could prove extremely harmful for the human race and for all species that share common space on planet earth. Indeed, there are many lessons in human history which provide adequate warning about the chaos and destruction that could take place if we remain guilty of myopic indifference to the progressive erosion and decline of nature’s resources. Much has been written, for instance, about the Maya civilization, which flourished during 250–950 AD, but collapsed largely as a result of serious and prolonged drought. Even earlier, some 4000 years ago a number of well-known Bronze Age cultures also crumbled extending from the Mediterranean to the Indus Valley, including the civilizations, which had blossomed in Mesopotamia. More recent examples of societies that collapsed or faced chaos on account of depletion or degradation of natural resources include the Khmer Empire in South East Asia, Eastern Island, and several others. Changes in climate have historically determined periods of peace as well as conflict. The recent work of David Zhang has, in fact, highlighted the link between temperature fluctuations, reduced agricultural production, and the frequency of warfare in Eastern China over the last millennium. Further, in recent years several groups have studied the link between climate and security. These have raised the threat of dramatic population migration, conflict, and war over water and other resources as well as a realignment of power among nations. Some also highlight the possibility of rising tensions between rich and poor nations, health problems caused particularly by water shortages, and crop failures as well as concerns over nuclear proliferation."