Deserts are roughly a quarter of the land on this planet.
They tend to expand at the edges. Currently some of our earthly deserts are expanding.
Would it surprise you to know that roughly 40% of humanity lives in arid or semi-arid regions?
I’ve already talked too much about how, during the Middle Ages, California experienced two serious droughts, lasting 140 years and 220 years.
In the desert Southwest of North America we know that New Mexico experienced a drought that lasted a millennium.
We call these mega-droughts.
Over the last 200 years modern European-Americans who invaded this landscape have been talking like that. We tend to talk like we were the first and only people to inhabit this land. So we’ve carefully gathered scientific data about the medieval mega-droughts from northern California. They encompass a time scale unlike anything we have seen in this modern era. We’re accustomed to freaking out about washing our cars and watering our lawns and how long our showers take during droughts that last a decade, at most.
None of us really can imagine what a drought of 200 years would bring us in terms of lifestyle changes.
We’re living in LaLa Land. We’re drinking up the last of our underground waters. We’d need another Ice Age to replace all those vast aquifers of living Pleistocene water under our feet, under the desert dust.
And it’s not just California.
Several years ago, people who study this stuff saw depletion of surface and groundwater supplies in the north American Southeast. The city of Atlanta, Georgia had a fearfully diminished water supply due to a drought. And satellite photos using ground-penetrating radar has shown global groundwater depletion in Asia, North America, Latin America, Africa, and the Middle East. If you search it out online, you can see those burning red hotspots of depleting groundwater. Non-renewable groundwater, in most cases.
If there’s no snowmelt or runoff to replenish it, it’s gone. If we’ve built and paved over areas where runoff might pool and sink happily into the ground beneath, it’s not going to happen. It’s not going to recharge the waters underground. Maybe it will flow into streams that flow into rivers? Maybe. Or maybe, at least in drylands, it will evaporate on its way across the landscape.
Beneath the driest regions of the Sahara, pollen samples indicate that the land was once tropical savannah and woodlands.
What will those people who dig up past landscapes find beneath their feet in a few hundred years in California?