Oases play a vital role as habitats and water sources in dryland areas, supporting 10% of the global population while only occupying approximately 1.5% of the land. However, climate change and human activities pose a threat to the delicate existence of oases. Recent studies have revealed changes in the size of oases over the past 25 years due to shifts in water availability patterns and the advancement of desertification into these moist refuges.
The existence of oases is under threat from natural and human activities. Recent research reveals that over the past 25 years, the world’s oases have both expanded and diminished due to changes in water availability and increasing desertification. Dongwei Gui, a geoscientist at the Chinese Academy of Science, led the study and emphasized the importance of oases in achieving United Nations Sustainable Development Goals.The study revealed that oases worldwide expanded by over 220,149 square kilometers (85,000 square miles) between 1995 and 2020, mainly due to deliberate projects to enlarge oases in Asia. However, desertification caused a loss of 134,300 square kilometers (51,854 square miles) of oasis during the same period, primarily in Asia, resulting in a net growth of 86,500 square kilometers (about 33,400 square miles) over the study period.
These findings emphasize the threat that climate change and human-caused stressors pose to these vital havens and can provide valuable insight for water resource management and sustainable development in arid regions.The research, which was published in the AGU journal Earth’s Future, focuses on the development and decline of oases in arid regions. Oases are crucial water sources in drylands, sustaining life and productivity in deserts for humans, plants, and animals. They are formed by groundwater settling in low-lying areas or surface meltwater pooling from nearby mountain ranges. The presence of a reliable water source is essential for the existence of an oasis.Oases are not formed by rainfall. Currently, oases can be found in 37 different countries; with 77% of them being located in Asia, and 13% found in Australia. Gui and his team sought to gain insight into the global distribution and changes of oases, and observe how they adapt to environmental changes such as climate variations, water availability, and human activities. By utilizing data from the European Space Agency’s Climate Change Initiative Land Cover Product, the researchers were able to classify land surfaces into seven categories: forest, grassland, shrub, cropland, water, urban, and desert. The team relied on satellite data for their study.Researchers studied green, vegetated areas in dryland regions to identify oases and monitored changes over 25 years. Changes in vegetation greenness were used to assess changes in land use and oasis health, which can be impacted by both human activity and climate change. The researchers also examined changes in land surface type to identify shifts in land use.
The study found that the global oasis area expanded by 220,800 square kilometers (85,251 square miles) during the 25-year period. The majority of this expansion was due to human-initiated conversions of desert land into oases using runoff water and groundwater pumping, leading to the creation of grassland areas.The growth of oases and croplands has seen a significant increase, particularly in China, where management efforts have been a major contributing factor. According to Gui, more than 60% of the growth can be attributed to these efforts. For instance, in China’s Xinjiang Uygur Autonomous Region, over 95% of the population lives within an oasis, leading to conservation efforts and a 16,700 square kilometer expansion of the oasis.
On the other hand, desertification has led to the loss of oases, countering the human efforts to expand them. The researchers found that there has been a loss of over 134,000 square kilometers of oasis land worldwide in the past 25 years. These changes to oases have been a result of various factors.About 34 million people worldwide were directly impacted by this phenomenon. From 1995 to 2020, oases experienced a net growth of 86,500 square kilometers (33,397 square miles), with most of the growth attributed to artificial expansion, which may not be sustainable in the long run. The study emphasized the importance of sustainable practices such as better water resource management, promoting sustainable land use, and encouraging water conservation and efficiency to ensure the long-term sustainability of oases, especially in the face of ongoing climate change.
According to Gui, humans overexploiting the diminishing groundwater can have a negative impact on oasis sustainability and contribute to long-term glacier loss. While higher temperatures can initially cause glaciers to melt, temporarily increasing water supplies for oases, Gui warns that as glaciers continue to disappear, the amount of meltwater will decrease, leading to the shrinkage of oases once more.
Gui also emphasizes the importance of international cooperation in maintaining oasis sustainability. He explains that the unique mechanism of oasis formation often involves multiple oases across several countries within a river basin, making transboundary cooperation essential.
The distribution and growth drivers of global oases from 1995 to 2020. Land Degradation & Development, 2021; DOI: 10.1002/ldr.3970
According to the research, oases have gained 85,000 square miles due to artificial expansion projects. However, they have also lost 52,000 square miles due to desertification and water scarcity. The net area gained is about 33,400 square miles, but this increase is primarily artificial and not sustainable. This emphasizes the need to address water scarcity and promote sustainable development. The study was published in Land Degradation & Development in 2021 and can be referenced as: Bochao Cui, Dongwei Gui, Qi Liu, Sameh Kotb Abd‐Elmabod, Yunfei Liu, Binbin Lu. Distribution and Growth Driver of global oases from 1995 to 2020. Land Degradation & Development, 2021; DOI: 10.1002/ldr.3970.The title of the article is “The Importance of Oases at a Global Scale” published in the journal Earth’s Future in 2024. The DOI for this article is 10.1029/2023EF004086.