IMAGINE you are in a desert. The air is dry, the landscape barren, but before you lies a teardrop-shaped pool. It is strangely lush, with sedges and tussocks of grass. Spiky succulents surround its salty shore. Peering into its crystal-clear waters, you observe various snails and furry brown domes that resemble frightened sea anemones. A shrimp-like creature paddles by. There’s a sort of leech, but it is lurid green. A small fish with red eyes and blue fins swims into view. Another fish, a flat-bellied bottom dweller, darts out of some weeds, flicking a cloud of mud. All these creatures are new to science.
It may sound like a nature lover’s fantasy, but this is real. It is an oasis in Australia’s arid interior, a place I have been lucky enough to visit and study. What’s more, it isn’t so unusual. Emerging evidence reveals that oases are often crucibles of biodiversity. These little pools in vast deserts are the ultimate isolated habitat, yet their antiquity, stability and weird chemistry have made them home to extraordinary organisms found nowhere else on Earth.
Oases still have secrets to impart. The exact locations of many of them remain unmapped. Meanwhile, others are threatened by demands for groundwater, a growing peril due to climate change and increasing human populations. That’s why I decided to establish the to save the world’s oases. This may sound ambitious, but recent developments in oasis rehabilitation show it can be done. Besides, the special cultural significance of oases and their crucial role in humanity’s past and future compels us to protect them.
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Water in the desert
There is something profoundly mysterious, even sacred, about water spilling from the depths of Earth in a desert landscape. Perhaps that is why the word “oasis” has such psychological power, characterising a place of safety and fertility in a barren world. Across cultures, the mineral-rich waters of these springs are bestowed with healing properties, and for millennia they were the primary treatment for human diseases and ailments. Despite the advent of modern medicine, oases remain important places for rest, for recuperation and to focus on well-being.
In humanity’s deep past, oases also played a crucial role in survival. The remains of early hominins are often associated with desert springs, prompting archaeologists to suggest that they may have been . Oases allowed trade routes to develop through the vast deserts of Asia and Africa, and they are still essential today.
Many cultures recognise oases as places of great mystical power (see “Sacred springs”). In several languages, they are referred to as “eyes”, perhaps because they have been seen as windows to the underworld. This is certainly the case from a geological point of view. All desert springs have their source in aquifers. Some of these hold groundwater in open cavities formed within soluble rocks, such as limestone. In others, the water lies between the grains of solid rock, including sandstone. Springs tend to form at geological structures, such as a fault or where two rock types meet, but the water may originate as rainfall in mountain ranges thousands of kilometres away from where it discharges.
The Great Artesian Basin in Australia, one of the largest aquifers in the world, seems to be an open system, recharged by rainfall, which then discharges through springs. In other places around the world, springs are fed by “fossil water” – with no rainfall currently entering the aquifer, the system must have been replenished during wetter climates of the distant past. One place that owes its existence to such springs is Djanet in south-east Algeria. Located in the heart of the Sahara desert, it receives an average of just 10 centimetres of rain annually. Yet, at times during the past 10,000 years, this region was a savannah watered by regular rainfall, as images of giraffes, cattle herds and flourishing human activity on local cliff faces attest. That ancient rain feeds the springs of the Sahara today.
While the value of oases for human culture has a deep history, their ecological significance has only recently started to emerge. In 1912, Czech explorer Alois Musil described a “pool of stagnant water… animated by various aquatic creatures” at an oasis at Ayn al-Tamr in the desert of Iraq, and suggested that it offered the prospect of a “very interesting study of the aquatic fauna”. No one has yet followed Musil’s suggestion. Indeed, the vast majority of oases haven’t been visited by researchers. Those that have, however, indicate that exciting voyages of biological discovery await us in Iraq and elsewhere.
The ecology of oases
A biological survey by myself and my colleagues revealed that oases around the world – specialised organisms with very restricted distributions. These include plants, flatworms, leeches, mites, crustaceans, snails, insects, spiders and fish. Our paper, published in June, documents 29 endemic species in springs at Ash Meadows in Nevada, within the Mojave desert. We found that springs at Cuatro Ciénegas, Mexico, are home to 60 endemic species, including seven species of fish, three species of turtle and a lizard found nowhere else on the planet. And at Byarri in the Great Artesian Basin, my colleagues and I have identified 36 endemic species, including the ones I described at the beginning of this article.
These local concentrations of endemic species are unrivalled by other habitats and locations. Some are that accumulate around the edge of mineral-rich springs. At all sites, the endemic species persist in oases not much larger than a garden pond. It is remarkable that animals that would die if left without water for even a few minutes have survived in such an isolated and tenuous habitat. Where did the specialised species come from, and how did they manage to persist in such tiny ponds amid a hostile landscape?
Genetic analysis, based on the rate at which mutations accrue during evolution, indicates that oasis-dwelling organisms diverged from their ancestors millions of years ago. This suggests that some species evolved when the continents had a different configuration and there were wet forests and streams where we now have desert. It is possible that, as these landscapes dried out, the widespread aquatic species contracted back to the springs and have survived as relics.
An alternative possibility is that improbable dispersal events occurred, allowing colonisation from moister environments. Imagine, for example, a seed germinating or an egg hatching after travelling in a dollop of wet mud on a pelican’s foot.
Either of these stories of evolution and survival in tiny ponds would be miraculous. What isn’t in doubt is that some springs have persisted over millions of years. Nevertheless, these ancient habitats are fragile and at risk from human activities.
A tale of decline has been well documented in Australia. For millennia, springs in the arid interior allowed Indigenous Australians to survive there. Only a few stories hint at the significance of these locations, but an leaves no doubt that the oases sustained life for many people. But when European pastoralists arrived in the 19th century, what they saw was a parched landscape barely suitable for farming sheep and cattle.
However, the springs hinted at an underground reservoir and became a window to their own demise. Holes were drilled through the rock layers, allowing the water to burst forth as gushing fountains: the Great Artesian Basin, which underlies one-fifth of Australia, had been discovered. Before long, there were thousands of boreholes and the water was directed along a network of open drains. A vast expanse of dry grassland had become productive pasture. Most of the water evaporated under the Australian sun and pressure in the aquifer dropped so much that, within a decade, half of the springs had diminished to a dribble and disappeared. We can only speculate at the extinction of endemic species.
The story of springs revealing aquifers, exploitation of groundwater, declining water pressure and the subsequent loss of oases has been retold time and again around the globe. As a result of climate change, population growth and economic development, demands for water are increasing. Groundwater extraction may seem like a solution, but, to succeed, it requires good planning and great care.
Libya offers a cautionary example. There, water demand has reached crisis point. In 1984, work commenced on the ambitious Great Man-Made River Project, which aimed to pipe water from the fossil water aquifers of the Sahara to urban centres along the Mediterranean coast and to supply water for irrigation and industry. The project is yet to be completed and civil strife in the past decade means it has faltered. Infrastructure is falling into disrepair and water piracy is rife. Despite the dream, there is still insufficient water for household use in urban centres, let alone for the expansion of agricultural development.
If groundwater is to help meet humanity’s growing need for fresh water, extraction must be sustainable. With judicious use of groundwater in deserts, it is also possible to preserve the oases and their extraordinary wildlife.
This much is clear from . The joint public-private initiative aims to restore lost groundwater pressure in the Great Artesian Basin by fitting the old boreholes with giant taps and diverting water from the open drains into plastic pipes. This benefits farmers because the water can be directed to a network of drinking troughs at targeted locations that extend further than the old drains. Conserving water maintains aquifer pressure, which makes it easier to deliver. With the recovery in pressure, the critically important springs at Byarri have doubled in size in just 15 years.
Mapping oases
The experience from Australia demonstrates that we can benefit from groundwater while still conserving or even restoring oases. However, a prerequisite to sustainable groundwater development globally is a thorough understanding of the hydrogeology of aquifer dynamics. We need to know whether a particular aquifer is being recharged and, if so, where the water is coming from. We need crucial information about the springs too, including why they occur where they do. And we also need to know about the ecosystems we are trying to conserve. Currently, we only have limited systematic surveys mapping where oases occur and an even cruder understanding of their biological value.
Pondering this problem during a covid-19 lockdown, I decided that there was something I could do to help. So, in 2020, I met people online who shared my vision, and together we formed the Fellowship of the Spring. We are now an eclectic group of 30 geologists, biologists, hydrologists, anthropologists, archaeologists and groundwater managers from 16 countries, including Libya, Iraq and Afghanistan, war-ravaged nations where water supply is a major issue. Our mission is to document springs, learn from the stories of local people and share information and experience to ensure the sustainable management of aquifers.
The Fellowship of the Spring has already been busy. Some achievements so far include: an inventory of springs in Namibia; sharing information about the impacts of lithium mining on oases with members of a community group in Chile’s Atacama desert; and revealing the significance and decline of springs along the Abu Jir fault in Iraq, which stretches 500 kilometres and has formed a divide between the eastern and western hemispheres since the dawn of human civilisation. We will continue to raise awareness of springs and what is at stake if they are lost.
Desert springs or oases have empowered people throughout history and across cultures. Now, we know that they are also remarkable crucibles of evolution. My hope is that the power and magic of oases can be harnessed again to protect them.
Sacred springs
Mythologies associated with oases are remarkably similar in desert cultures around the world. The springs, which are gateways to vast, invisible subsurface realms, are often seen as spiritual connections to the underworld, inhabited by dead ancestors or supernatural beings.
The association of springs with oracles is remarkably common across many cultures. Oases are sacred for some Native American peoples, with springs said to provide access to spirits generating prophesy and prosperity. Springs had a similar function for some Indigenous Australians. Likewise, the ancient Egyptians consulted a human oracle at the Siwa oasis, which is sustained by desert springs.
One foundation of ancient Greek civilisation was the Oracle of Delphi. The supposed source of this soothsayer's power has become an enduring mystery, as during the fall of Greece, the temple at Delphi was ransacked, its riches were looted, the buildings were destroyed and the inscriptions were defiled. However, we do know that prophesies were thought to be delivered by a woman with the power to serve as the mouthpiece of the great god Apollo, and that before she commenced her work, she would bathe in a spring. Given what we know from other cultures, may well be the mysterious source in the oracle myth.
Rod Fensham is a botanist at the University of Queensland, Australia. He has been studying Australian oases for 25 years
