The western United States has been experiencing an event known as a mega-drying plant since the year 2000. However, studies indicate that climate change may intensify the phenomenon, something that can already be noticed through the great fires that affect the region and the lower beds of rivers used for navigation, such as Colorado, which needed to have its waterway closed.
Megassecas are quite rare and usually last for decades. Researchers believe that at least 4 of these phenomena occurred in the USA: in the late 800s, in the mid-1100s and in the late 1500s. They could be determined through fossil records of trees compared to those of today. Through the analysis of the rings inside their trunks, it is possible to determine the soil moisture in the last 1200 years.
In the conclusion of the specialists, the current mega-drying should only be less than the one that occurred between 1575 and 1603, but by a very small difference. “The first two decades of this drought look like the first two decades of all the mega-pans,” said Dr. Park Williams of Columbia University, the study’s lead author.
And as much as megassecas are normal events in the region, the researchers warn that the current one is being aggravated by climate change. Phenomena such as La Niña, for example, leave the North American southwest and northern Mexico quite arid - and this has happened frequently in the past 20 years.
Another detail is that, since 2000, temperatures in the region have risen 1.2 ° C, making the warmer air retain more moisture, which is removed from the soil. The two most important water reservoirs in the area, Lakes Powell and Mead, have drastically reduced their volume in recent years. As a result, it was necessary to use underground aquifers to maintain agriculture in the most affected states.
To calculate the effects of man-made climate change, scientists used 31 different computer models. With them, it was possible to determine that the drought of the last 20 years would only be normal if there was no human interference; however, it has become up to 47% more severe. “Even without climate change, we would still have a drought, but it wouldn’t be that big,” explains Williams.