Most desert oases are gardens that people built and keep alive
The storybook oasis is a pool ringed by palms that nature simply provided. In reality, most oases are human creations. Water has to be there, but it takes wells, canals, underground tunnels and constant weeding to turn it into a place where people can live, farm and rest their caravans.
Natural ones do exist. Rain seeps underground, gets trapped by impermeable rock or channelled along faults, and seeps up somewhere; birds drink there and drop seeds, and plants spring up at the edge. But human know-how does most of the work. Saharan communities dug tunnel systems with regional names such as foggara and khettara, and in Oman, networks called aflaj tap aquifers through channels cut into the ground or the rock and have avoided serious salt build-up. The word itself hints at settlement: it reached English through Greek and Latin from Egyptian, and its Coptic descendant means a dwelling place.
A working oasis is farmed in three storeys. Date palms form the canopy and provide both income and a staple food. Beneath them grow apricots, figs, olives and peaches, and at ground level, where moisture lingers, vegetables, cereals such as barley and millet, and animal fodder. The layers slow the wind, cast shade and release moisture, producing what is called the oasis effect. Measurements in several oases found potential evaporation reduced by 30 to 50 percent compared with the surrounding land. Manure from herders' livestock keeps the soil fertile.
The payoff is out of all proportion to the area. Oases in West Asia and North Africa cover only about 10,000 square kilometres yet support around 10 million people, and the Sahara holds about 90 major ones. Some have been lived in for a very long time; digs at Ein Gedi near the Dead Sea show settlement from 6,000 BC. Because caravans had to stop for water, whoever held an oasis often controlled a trade route. The Silk Road hopped between oasis towns such as Turpan and Samarkand, and Saharan hubs like Ghadames and Kufra linked routes running in every direction.
That fragile balance is slipping in places. Morocco has lost two-thirds of its oasis habitat in a century to heat, drought and water shortages. In Egypt's Western Desert, oases such as Siwa and Kharga once had flowing springs that overpumping for new farmland has dried up, and modern pumps can undermine traditional ways of sharing water.
Source: Oasis
