chapter 17 summary i have lived a thousand years

It is estimated that drought results in more crop yield losses than by all pathogens combined. Notably, the salinization of irrigated lands in Mesopotamia and filling up of ditches with sediments, often dug and maintained by enslaved peoples, resulted in lost land fertility and an inability to sustain large centrally governed civilizations.

But water management failures were also responsible for the collapse of societies. Moreover, new water management schemes forced societies to get organized, work together on irrigation and drainage schemes, and develop laws on water allocations. This led to important innovations like markets, writing and transportation. High yields in drained and irrigated areas allowed for the development of trade specialization because crop surpluses no longer required everyone to provide their own food supply. Examples include Mesopotamia, literally the “land between the rivers” Tigris and Euphrates, the lower Nile Valley and northeastern China. In fact, the first major civilizations and population centers emerged when farmers started to control water, resulting in more consistent yields and stable food supplies. It is estimated that more than half of the global food supply depends on some type of water management. Growing seasons around the world rarely have the right amount of precipitation, and deficits and excesses of water are the most significant overall yield-limiting factors to crop production. … When evaporation rates are high, sustained irrigation can generate enough salt to eventually poison the crops. Groundwater in semiarid regions usually contains a lot of salts. Soils for Urban Farms, Gardens and Green Spacesīut the irrigation that nourished Mesopotamian fields carried a hidden risk. Irrigation Management at the Farm Level.Environmental Concerns and Management Practices.Recycled Wastewater and Desalinized Seawater.Managing for High-Quality Soils and Focusing on Organic Matter Management Soil Degradation: Erosion, Compaction, and Contamination What Is Organic Matter and Why Is It So Important Or call to order: (301) 779-1007 Table of contents

Chapter 17 summary i have lived a thousand years