There are two aspects of the impact – 1) in terms of deserts itself including creatures that originally live deserts 2) in terms of deserts’ expansion to external environments
Within Deserts
Although desert species are thought to be live in the hottest and driest places around the world, they can only thrive under limited conditions. It takes thousands and millions of years for creatures to adapt to new environments, but climate change is happening dramatically within 100-200 years.
According to a study on sensitivity to climate change for two reptiles, a moderate climate change of +2 °C and -50 mm precipitation, desert tortoises’ suitable habitat was reduced by nearly 88% in the Sonoran Desert and nearly 66% in the Mojave Desert regions.
The distinctive Joshua trees (Yucca brevifolia) in Joshua Tree National Park could lose up to 90 percent of its distribution if we increase temperature by +3 °C.
What is more, as creatures need to move to cooler and higher-elevations areas, another problem arises – mismatch and imbalance. Joshua trees are hard to move with in 10 years, where animals are more free to find new inhabitants. Even within critters, movement speeds are different, e.g. tortoises are slow-moving while side-blotched lizards are faster. But ecosystem is constituting of species depending on each other. The difference in moving speeds alone will cause lots of chaos.
Outside the Original Deserts
Desertification has been talked up for years. In a 2018 study, Sahara Desert has expanded 10% since 1920. And the newest desert on earth is Aralkum Desert, which appeared since 1960 on the seabed once occupied by the Aral Sea.
As deserts are mostly measured by rainfall, it would be more interesting to look at land degradation. The World Atlas of Desertification claimed that “Over 75% of the Earth’s land area is already degraded, and over 90% could become degraded by 2050; Globally, a total area half of the size of the European Union (4.18 million km²) is degraded annually, with Africa and Asia being the most affected.” In a 1991 study, 35% of the world’s land surface is currently at risk and more than 20 million hectares are reduced annually to near or complete uselessness.
The measures are different, but the trend is certain.