The large and most important factor was the heavy depends on the environment and the land that these civilizations had. With the large expansion of civilizations new forms of technology where developed. The granary regions, which contained most of the good growing crops, formed irrigation ditches. Most large developed cities where riverreins and depend on the river for all their agriculture purposes. Every year the cities would wait for the river to flood so it would fertile the land with silt from the river. Civilizations depended on these large annually floods to occur. Ponting explains, Agriculture involves clearing the natural ecosystem in order to create an artificial habitat where humans can grow the plants and stock the animals they want. The natural balance and inherent stability of the original ecosystem are thereby destroyed( 68 Ponting). Due to deforestation (wood for fires, clearing land for agriculture, houses) and erosion (from clearing the trees) change the climate over hundreds of years and stopped the floods from happening and brought a huge drought or a very wet year which cause crops to decline in yield an food production. This cause falling nutritional standards and increased diseases and other infections. With the cause of poor crops comes starvation and a decline in domesticated animals. Ponting says, clearing forests, therefore ran the risk of bringing about soil deterioration and declining crops yields and this would be exacerbated by lack of domesticated animals to provide manure to maintain soil structure and fertility (Ponting 82). Due to these occurrences, many of the most powerful civilizations where weak and were easily invaded by other civilization and easlily to form a rebellion against them. Many civilizations expanded and couldnt control their expansion, this could have been because of poor leadership. Leaders that had power but wanted more by invading others and to have the big populations where us...
