Threats in oases
Oasis are at the same time fertile and fragile ecosystems. Oasis can experience a expansion (oasification), due to plantation of new lands and the use of sustainable and modern farming practices or, in the other hand, could experience a retraction (desertification), by inducing range constriction and agricultural land degradation due to the combined effects of land abandonment, severe climate conditions, and urban expansion. Oasis ecosystem in arid and semiarid regions are super sensitive to land use changes because of:
(1) Over-using inland river water and over drawing ground-water leading to the shrinkage of oasis, including the decline and death of natural vegetation, the decline of groundwater, drainage of lakes etc.
(2) Poor irrigation management leading to salinization, especially in coastal oases, which aquifers are exposed to the mixture with marine water from the sea.
(3) Over-reclamation, overcuring for firewood and overgrazing which leads to grassland degradation.
(4) Failure to maintain shelterbelts in and around the oasis areas, which leads to the invasion of windblown sand.
Oases are also affected by climate change. It is expected a decrease in annual rainfall in some of the drylands of the world and an increase of monthly minimum and maximum temperatures. At the same time, human water demand is expected to increase. This will, finally, increase the irrigation demand on oases. The presence of the oasis maintains the climatic conditions for self-preservation. But this “Cold Island effect” or “oasis effect” could be compensated or overwhelmed with some climate changes like the global warming or the “urban heat island effect”, specially having into account that usually oases are the main areas in which human could survive in drylands.