This unit analyses four relatively strong civilizations both in the New World and the Old over the past two thousand years that weakened so much that their civilizations ended, became memory and eventually legend. There is ample evidence that their populations' use of the natural resources so stressed their fragile ecosystems that when the climate changed they were unable to continue with their lifestyles. We also make a comparison with the climatic shift that we humans have caused in our pursuit of progress' and the unwillingness of our industrialists and political leaders to recognize its magnitude. Therefore we analyze some of the evidence that global warming is already having on Houston and the Texas Gulf Coast wondering if the excessive modifications to the landscape in order to accommodate to the intensive demands of industry, agriculture, construction and urban demands will hold firm.

The lesson plans are designed to awaken in fifth graders and older curiosity about the planet Earth and its physical morphology, the different causes of climate changes, human's proper usage of natural resources. Woven into all of this is the effort to rouse in the students, an acceptance that we are part of the natural world and as such should strive to find sustainable ways to satisfy our real needs.

(Developed for Science, Physics, Biology, Earth Science, Social Studies, Geography, and Populations, grade 5; recommended for Science, Physics, Biology, Earth Science, Social Studies, and Geography, grades 4-12)