La scomparsa delle oasi
Le oasi che hanno segnato e accompagnato la civiltà, con le loro linee d’acqua, le verdi macchie, il percorso delle rotte commerciali – nel deserto del Sahara come nei terreni rocciosi del Colorado – rischiano di sparire. Minacciate dalla nostra cultura “artificiale dell’acqua e dell’esotismo” ( fontane e giochi d’acqua , piscine, parchi acquatici e giardini tropicali nelle città e metropoli…) Un articolo originale e molto interessante
di Rebecca Lawton
Seen from the air, the single verdant parcel of land with its straight borders and sharp edges resembles a green postage stamp pasted on a great expanse of manila envelope. Inside the boundary, a screen of trees hides a palatial estate, acres of emerald turf, a paved circular driveway, and an extensive array of tumbling, marble fountains. Outside the rectangle, a hot, rock-strewn fan of tan alluvium extends unvegetated and unwatered for half a kilometre to another such parcel, then another, then another. Toward the city centre eight kilometres away, residences cluster closer together but emulate the lush feel of the outlying estates with their surfeit of palm trees, water features and improbably green turf.
Downtown, a shimmering strip of casinos, restaurants, luxury shops and lounges lures visitors indoors off the sunburnt street. Fountains and gazing pools convey a sense of plentiful water, as if the strip were supplied by healthy dousings of rainfall. One cannot tell by looking that the city, Las Vegas, normally receives less than 11 centimetres of rainfall a year in a climate where summer temperatures regularly soar above 32 degrees Celsius (90 degrees Fahrenheit). To build an oasis at a desert resort requires more sleight of hand than a card shark playing a casino. Yet Las Vegas, like other arid communities, routinely pumps water for just this purpose from underground or outlying systems – in this case, the Colorado River impounded in Lake Mead, a reservoir 50 kilometres away.
The green succour of true oases has been part of humankind’s experience for millennia, occurring where precious below-ground springs and aquifers nearly reach the surface. For centuries, oases have marked the locations of communities and trade routes. In recent generations we’ve extended the oasis habit into our built environment, pumping water into faux oases – such as Las Vegas – to complement what nature provides. But our human impulse to convert the desert, to build oases wherever our surroundings are arid, has produced an 11th-hour crisis of water mismanagement and shortages worldwide.
A landscape deemed forsaken, ‘desert’ derives from the Latin desertum, ‘something left waste’. In the geographer’s lexicon, a desert is an area receiving less than 25 centimetres of rainfall a year. The world’s largest are the polar deserts, each approximately 14 million square kilometres of ice, snow and tundra in the Arctic or of bedrock in the Antarctic. Next comes the Sahara, 9 million square kilometres of gravel plain, sand and dune spread over 13 countries and covering a quarter of the African continent. After that, the Arabian Desert comprises 2.5 million square kilometres and reaches into six countries. Equal to one-fifth the area of the continents, often inhospitable due to extreme temperatures and lack of water, deserts are also the settings where natural oases, some of the most appealing land- and water-forms on the planet, can be found.
The moist, fertile zone of the oasis consists of a central pool of open water surrounded by a ring of water-dependent shrubs and trees, notably palms, which are in turn encircled by an outlying transition zone to desert plants. In contrast to the vast expanse of the world’s deserts, the oasis ecosystem is relatively minute, rare and precious, the largest measured in dozens and hundreds, rather than millions, of square kilometres.
Oases figure prominently in human survival and evolution. The earliest people lived and hunted around surface water, matching their ranges to the persistent springs and pools that also attracted wildlife and watered vegetative sources of food. Paleontologists studying early evidence of Homo sapiens at Olduvai Gorge, Tanzania found that our forebears probably relied on isolated oases when other potable water became scarce during times of drought.
Oases also formed bridges between larger bodies of water, anthropologists hypothesise, allowing humans to migrate within and ultimately out of Africa. Natural oases determined the trajectory of trade routes and desert settlements. From the sure signs of underground water signalled by a grove of fan palms in the Sahara to the early dwellings along great rivers on the Colorado Plateau in North America, water determined the locations of communities and pathways among them.
The longest known network of trade routes, the 7,400-kilometre Silk Road across Africa, Asia and Europe, traced its course from water hole to water hole, relying on oasis communities such as Turpan in China and Samarkand in Uzbekistan. The Darb el-Arba camel route in middle Egypt and Sudan, the Moroccan caravan route from the Niger to Tangier, and the aboriginal foot trails in the Mojave Desert in the American southwest were all oasis-linked routes that otherwise would have been impassable.
Over time, cultures integrated the oasis experience of rest and recreation into the built world. In ancient Rome, thermae (large-scale imperial baths) and balneae (small-scale public and private baths) were created through elaborate systems of aqueducts leading from rivers and springs to most towns and villages. The public baths were the community centres of their time, where citizens could meet for conversation, soaks, massage and exercise. The Latin adage for the healthful properties of water, ‘In Aqua Sanitas’, conveyed the philosophy that water immersion for recuperation and rejuvenation was central to good health and even good citizenship.
In the tradition of Rome, resort towns elsewhere became popular, their engineered waterworks full of healing waters from naturally occurring mineral springs and shallow stores of groundwater. The community of Spa, Belgium, gave its name to a soaking custom replicated worldwide: toplice in Slovenia, bain in France, Bad in Germany,fürdő in Hungary, città thermale in Italy,hot springs in America – destinations that were and are cultivated to offer respite to those who want to ‘take the waters’.
In arid regions, recreating the experience of healing waters requires some doing. Water must be pumped from a natural source up inclines, over artificial ledges, often into buildings or fenced areas where cement-rimmed swimming pools emulate the grass-sloped natural pool. Resort gardens are made to order, their fully mature trees installed by cranes and work crews, their water needs met through irrigation and timed sprinkler systems. The hot dry desert of the Las Vegas valley, one of the world’s greatest faux oases, serves up a modern-day mirage – the fantasy that we can keep taking large quantities of water from elsewhere to make the desert green, without paying the price.
The oasis has beckoned and tantalised us for millennia, offering the weary desert traveller a dip in an open pool, the green shelter of palm fronds and the relief of shade and refuge. These are not just creature comforts; they also enhance health.
As it happens, water immersion also enhances the function of the brain, by improving the ability of blood to transport oxygen and nutrients to it. In a 2014 study from the University of Western Australia published in the American Journal of Physiology, subjects immersed heart-deep for 10 minutes in a tank of water at 30 degrees Celsius (86 degrees Fahrenheit) experienced greater cerebral blood flow over the duration of immersion.
Similarly, an oasis’ green foliage is likely to promote wellbeing. Testing what nature‑lovers have long intuited to be true, researchers in environmental psychology are measuring the electrical response of the brain to green space. An article on the ‘urban brain’ in the British Journal of Sports Medicine in 2015 reports that subjects exhibited ‘lower frustration’ when moving into natural areas and ‘higher engagement’ when moving out. Compared with brain response to other zones, such as shopping or commercial districts, the improved mental state measured in subjects moving along paths in green zones showed the potential for restoration and recovery from stress.
The oasis also helps us stay focused. The common experience of feeling a kind of brain fog in the hot sun isn’t just imagined; it’s real and measurable. Studies have shown that mammals, including humans, require a two- or three-fold increase in natural evaporation to maintain reasonable body temperature when exposed to desert sun; conversely, slipping into shade increases performance and physiological measures. Getting to an oasis at the end of a day spent in desert heat fulfils the simple and necessary function of preventing overheating. Brain temperature stays about 0.2 degrees Celsius higher than the rest of the body, says a 2011 study from the University of Copenhagen. In hot environments with no relief, we become unable or unwilling to continue walking or performing other forms of exercise. The simple break of an oasis can keep us on track.
Given all this, it makes sense that the resort or spa, the modern emulation of the ancient oasis, adds therapeutic treatment to the natural benefits of water, plants and refuge. Some benefit comes through stimulation of endorphins, morphine-like molecules associated with the experience of deep pleasure. Candace Pert, the late American neuroscientist and pharmacologist, discovered that endorphins attached to opiate receptors not just in the body, but also the brain. Ultimately, an entire system of hormones and receptors was discovered in neuroscience labs, powering the nascent field of psychoneuroimmunology – the study of an interconnected brain-body loop driving mood, health and disease. The ‘way in which [chemicals] circulate through the body, finding their target receptors in regions far more distant [from the brain] than had ever been thought possible,’ Pert wrote in her book, The Molecules of Emotion (1997), ‘made the brain communication system resemble the endocrine system, whose hormones can travel the length and breadth of our bodies.’
Poised to deliver that sense of wellbeing to the length and breadth of our bodies and brains are faux oases, today represented by the $40 billion resort and spa industry, one of the fastest-growing sectors of leisure travel worldwide. Wherever there are spas, travellers can find water, in whirlpools, steam rooms, fountains, mud baths and other assorted features, all in the service of relaxation, rejuvenation and health.
In arid regions, the bulk of water is, of course, already directed to agriculture and urban use. Yet desert biomes also host tourists, who come for built oases, above all else. In 2007, the architect Aziza Chaouni at the University of Toronto conducted an investigation in the Sahara Desert, where a resurgence of tourism in the 1980s ‘induced both the extension of existing colonial accommodations and the creation of new large hotels, a phenomenon which not only drained the scarce water resources but also shifted local economies from agricultural to service‑based’.
Installing greenery and engineered water features to create resort complexes stretches already-exhausted water budgets in Dubai, where 2.4 million residential users consuming 492 litres per capita daily long ago outgrew freshwater supply. A destination for foreign tourists and workers, Dubai has the advantage of being a wealthy seaside resort that can meet its water needs through desalination plants. Though roughly twice as expensive as water from recycling or impounding, desalination is still an option in oceanfront locales.
Land-locked Las Vegas, on the other hand, is restricted to freshwater supplies. With 603,000 residents inside the city limits, more than 2 million in the greater metropolitan area, and a tourism-based economy, the area’s once-adequate surface and groundwater no longer meets its needs.
The Colorado River fulfils 86 per cent of the Las Vegas valley water portfolio, apportioned and piped annually to the state in the amount of 500,000 acre-feet (617 billion litres). The river allotment is supplemented by groundwater, which contributes another 10 per cent to metropolitan and urban use; recycled water makes up the last 4 per cent. The Southern Nevada Water Authority, which controls supply, estimates that casinos and resorts use 32,000 acre-feet of Colorado River water (7 per cent of the apportionment) and 4,000 acre-feet of groundwater from private wells, or 36,000 acre-feet in all.
A large quantity of this water – some 60 per cent of all water delivered to homes and businesses in Las Vegas – goes to irrigate landscaping and create water features, according to the Water Authority. An estimated 70 per cent of residential use and 20 per cent of casino and spa use is applied outdoors on turf, landscaping and swimming pools.
In fact, in Nevada, most outdoor use is consumptive – that is, fully used and lost to the system. As a result, groundwater has declined more than 100 metres and associated land has sunk several metres. Resulting earthquakes, irreversible ground collapse and property settling have caused billions of dollars’ worth of damage in the Las Vegas valley alone.
Similarly extensive pumping of groundwater from the San Joaquin Valley aquifer system in California for agricultural and urban use has ‘caused groundwater levels to decline’, according to the United States Geological Survey, ‘resulting in as much as 28 feet [8.5 metres] of land subsidence’. Once an aquifer is drawn down, the underground space for it closes up, and the land’s ability to hold water in its best, natural location – the cool underground – is eliminated as an option.
Pulling surface water from rivers also puts civilisation at risk. When flow is reduced too much, the water remaining in streams can no longer sustain native aquatic life or even the habitat critical to climate resilience for a range of species, including humans.
Taken to an extreme, mismanaging water supply destabilises cultures. The Syrian refugee crisis can be understood as a direct result of water instability driven by a changing climate. According to a 2014 United Nations report on drought in the Middle East, an estimated 800,000 people have lost their livelihoods due to water mismanagement in the region. ‘Water scarcity is forcing people off the land,’ said Hussein Amery, a Middle Eastern water management expert at the Colorado School of Mines, in an interview with National Public Radio in 2015. ‘These refugees are very much water refugees, a product of water scarcity in the region.’
In the American West, much of the water mismanagement that has drawn down stores stems from the creation of the faux oasis, what the late water resources consultant Marc Reisner called the ‘Cadillac desert’. ‘In the West, it is said, water flows uphill toward money,’ he wrote in Cadillac Desert: The American West and Its Disappearing Water(1986). ‘And it literally does, as it leaps 3,000 feet across the Tehachapi Mountains in gigantic siphons to slake the thirst of Los Angeles, as it is shoved 1,000 feet out of Colorado River canyons to water Phoenix and Palm Springs and the irrigated lands around them.’
It is the 11th hour at the oasis – 11:59 pm, in truth – past time to act. With the faux oasis a fact of life, and water a dwindling key resource increasingly at risk, our best next step is to cut consumptive use.
The Pacific Institute, a research and outreach organisation in Oakland, California that ‘creates and advances solutions to the world’s most pressing water challenges’, evaluates water use for improved conservation and sustainability. The institute’s analysis of resort consumption concluded that increasing water needs can be met with no change in guests’ water use habits (and presumably no decline in their quality of experience) if hotels and spas install technologies such as water-saving showerheads, low water-use toilets, and upgraded appliances in laundries.
Even more can be done. The Green Spa Network of Sebastopol, California, a leader in the effort to reduce the water footprint, recommends that spas use native plants – trees, shrubs and herbs naturally found in the arid and semi‑arid environment being landscaped. A founding member of that network, the Osmosis Day Spa Sanctuary in Freestone, California, has not only changed landscaping but also installed a greywater system on site. The system, which processes and recycles wash water from laundry right at the spa, has cut water use at Osmosis by 3,800 litres per day. In a state where severe drought is in its fourth year, wildfires are burning in increasing size and number, and reservoirs are depleted, all water savings count.
In California in general, simply re-landscaping residential, commercial and institutional gardens with native plants and other drought-tolerant species could reduce water use by 1.3 million acre-feet annually. This reduction, according to the Pacific Institute and National Resource Defense Council, would be ‘equivalent to a statewide per capita use of 30 gallons per day [114 litres]’ when the current use is 140 gallons per day [530 litres].
‘At home, widespread adoption of water-saving appliances and fixtures, along with replacement of lawns with water-efficient landscapes,’ says the Pacific Institute, ‘could reduce total residential water use by 40 to 60 per cent, saving 2.2 million to 3.6 million acre-feet per year,’ for savings of up to 5.2 million acre-feet per year overall.
Our emotional desire for oasis might never leave us, but if the natural oasis is to endure, the faux oasis might have to hold sway only in our minds. Water in the natural world – in wild rivers rather than engineered canals, natural lakes rather than reservoirs, true falls rather than recirculating fountains – is the fix. Draining our actual water supply to create the faux oasis endangers the true refuge and puts us all at risk.