The climate and readily available natural resources determined building styles and construction techniques in ancient Mesopotamia. These factors not only influenced the appearance of buildings and how they were decorated but also their survival in our archaeological records.
The geography of each area and the natural resources found there affected the ways that people lived. Northern Mesopotamia is made up of hills and plains. The land is quite fertile due to seasonal rains, and the rivers and streams flowing from the mountains. Early settlers farmed the land and used timber, metals and stone from the mountains nearby.
The civilized life that emerged at Sumer was shaped by two conflicting factors: the unpredictability of the Tigris and Euphrates rivers, which at any time could unleash devastating floods that wiped out entire peoples, and the extreme fecundity of the river valleys, caused by centuries-old deposits of soil.
Thus, while the river valleys of southern Mesopotamia attracted migrations of neighboring peoples and made possible, for the first time in history, the growing of surplus food, the volatility of the rivers necessitated a form of collective management to protect the marshy, low-lying land from flooding.
This area is called the fertile crescent. The total precipitation is indirectly known from the deposit of organic material in the sediments on the sea floor in the Gulf of Persia, from radiocarbon dates in lake sediments. The ratio of the Oxygen-18 isotope in lake sediments is an indicator of the total lake volume of water. There is no systematical trend (e.g. it is not getting dryer and dryer) in the last 5000 years (historical times), but there are three large scale dry periods effecting the entire Near East: 3200-2900, 2350-2000 and around 1300 BCE.
Aside from the fertile soil and the rivers, however, Mesopotamia had few natural resources. Lacking wood, for example, the Mesopotamians built their dwellings out of mud brick, one resource that was plentiful. Such bricks were also used to build defensive walls around the city-states, which had no other means of protection. What the Mesopotamians lacked in natural resources they could trade for; throughout Southwest Asia, they traded figs, dates, grain, and other crops for items such as gold, ivory, and other precious stones.
The Sumerians made their clothing by using the natural resources that were available to them. Clothing was made from wool or flax which Sumerians could raise and harvest. (Flax is a plant with blue flowers. The stems of these plants are used to make the clothing.)