THE OASIS MODEL

Pietro Laureano
Faculty of Architecture, Polytechnic of Bari (Italy)
E-mail: ipogea@ipogea.inet.it
Web site: www.laureano.it

The main, defining environmental features of arid or desertified areas can be summarized as a lack or absence of meteoric and surface water, scarce vegetation and lack of soil. In deserts, rocky surfaces look bare without the soil which has been dehydrated by the sun and crushed by thermal expansion and blown away by the wind because there are no trees to offer shelter.

Plant cover is the result and the prior condition for the existence of topsoil. Seeds can put down roots in the soil and derive sustenance from it. For their part, plants protect the humus and ensure that it is constantly regenerated thanks to dry cast-off plants. Desert surfaces which are bare of vegetation are exposed to the harsh atmospheric agents, to the brutality of erosion which crushes the rocks and produces sand. All of this in turn reinforces the erosion factors and worsens the drought in that hard silicon particles are blown away by the wind, thereby becoming an abrasive force which can destroy even the hardest of rocks. Sand contributes to the disappearance of running surface water by settling in and filling up river beds, thus forcing the water to change its course and to become stagnant over vast surface areas where the water can evaporate or seep below ground. Where there is no shade, exposure to the sun can create high temperatures which act like a pump and suction up the moisture from underground strata. The outcoming water carries a salt load and when it evaporates it leaches salt into the soil, sterilizing it and killing vegetation. It is a closed circuit: soil, water and vegetation are interconnected in such a close way that the absence of any one factor can cause the absence of another factor with a multiplying effect. Once the cycle of desertification has begun it continues speeding up.

These general trends can be interrupted in given specific situations which create environmental niches and microenvironments which run counter to the overall cycle. A shallow depression collects moisture, a rock casts a shadow, a seed thrives. In this way, positive feedback begins: the plant generates its own protection against the sun rays, it concentrates water vapour, attracts insects which will produce biological material, it creates the soil which will then nourish it. Thus, a biological system is produced which uses other organisms making their own contribution. A symbiosis is set up; a microcosmos is created as the result of co-existence.

The peoples inhabiting the Sahara use these processes to create their oases. Often, the origin of an oasis was a simple palm tree planted in a shallow depression in the soil and surrounded by dead branches protecting it from the sand. Over time, vast cultivated stretches grew along terraced canyons or else green archipelagos rose up from the sand dunes thanks to diversified and complex water production techniques, land organization and the creation of a microclimate. Though on entirely different scales, the same principle, the oasis effect applies: a virtuous cycle is established which can run itself and regenerate itself.

These techniques are typical of settlements in the deserts of the Sahara and Arabia and are widespread throughout the Near East and on Mediterranean islands and peninsulas and in a number of geographical areas. The features they share are fragmentation and geomorphological harshness, arid climates and unusual humidity conditions. Thus, what we have is an enormous and quite varied reality of oasis systems which are autopoietic and self-sustaining in a gamut of conditions: adobe oasis cities such as those along the dry river beds in Yemen which use the inhabitants' organic waste to fertilize the sterile sand and render the sand suitable for use in bold architectural designs; stone oases which from prehistorical times onwards have been dug out of the tufa stone of the Sassi of Matera and in the Gravine and Lame of Apulia where the water necessary for survival is condensed in the caves and on the adobe constructions; religious oases carved out of the erosion valleys in Cappadocia, in Palestine, in Thebaid and in Ethiopia organized in the form of hermitages and walled gardens irrigated by drainage tunnels, cisterns and ditches; sea oases spread throughout the arid islands of the Mediterranean and the Red Sea and supplied by air-borne sources of water; and even oases of humid forests where due to the special karst environments no surface water courses can form, which makes the settlements completely dependent upon meteoric water collection and conservation, such as the chultun in Yucutan, Mexico.

Thus a wider oasis model takes shape. It includes those types of human settlements which are able to create conditions hospitable to life in adverse situations, thanks to appropriate use of local resources and strong community links. They are cultural systems in which all elements are tightly connected and in particular, technique, symbolism and aesthetics cannot be separated.

The relationship between the individual and the world sets up a pact between culture and nature; the symbol and the tradition are witnesses and guardians of this pact which ensures the maintenance of universal harmony. It is in this solid relationship, that man can find consolation to his precarious existence, and the environment becomes holy which is necessary for its safeguard and protection. The strict link between actions and nature’s harmony imposes a set of forbiddances, bonds and prescriptions since even the simplest actions can contribute to the maintenance of universal balance. Therefore, in the oasis the constant relationship between microcosm and macrocosm is not a metaphysical idea but it is an ethical principle based on specific material needs.

Pietro Laureano
Architect specializing in urban and landscape restoration, lecturer on Urban and Territorial History at the Polytechnic of Bari -School of Architecture- and Director of IPOGEA. Italian Research Centre on Local and Traditional Knowledge.
His experience includes eight years in the Sahara desert within the framework of oasis conservation projects. He is UNESCO’s expert in arid zones, Islamic civilization and fragile ecosystem and the Italian representative to the UNCCD (United Nations Convention to Combat Desertification) Committee on Science and Technology)