A new study on climate change shows that California’s drought-like conditions could last another 50 years, and possibly for thousands of years, a result which in either case would have dramatic repercussions for agricultural production and food prices across North America.

The 21st century has brought with it a period of extended drought in the state of California, with 10 of the past 14 years registering as drier than normal and the last three years recorded as the hottest and driest since 1895. As a result, the state’s agricultural output has decreased, affecting fruit and vegetable prices across the continent and leaving both producers and consumers wondering how long the downturn will last.

The news on that front may now be a little clearer -and more dismal- as an international team of scientists including researchers from Western University in London, Ontario, have released a new study of California’s geological history which confirms that during past periods of drought, dry conditions in the region normally lasted anywhere between 50 years to thousands of years at a time.

Researchers analyzed sediment core samples from the bottom of Kirman Lake, a small freshwater lake in the Sierra Nevada mountains about 280 km east of Sacramento and found that from 6,000 to 1,000 BCE and again between 950 and 1250 CE the region was caught in severe drought.

“When you have arid periods that persist for 60 years, as we did in the 12th century, or for millennia, as we did from 6,000 to 1,000 BCE, that’s not really a ‘drought.’ That aridity is the new normal,” says Glen MacDonald, professor of Geography at UCLA and lead author of the study.

The authors say the markers in the lake’s sediment composition, including charcoal deposits from wildfires and fossils from sagebrush, mollusk shells and algae, told the tale of local climate conditions throughout the years and indicated when the lake had dried up and become marshland and when it had filled in again.

The results match other geological accounts which also describe a general aridity both during the period known as the mid-Holocene between 6,000 and 1,000 BCE, commonly attributed to a slight shift in the Earth’s orbit that affected the amount of sun received in the Northern Hemisphere, as well as during the period known as the medieval climate anomaly between 950 and 1250 CE, explained by a decrease in planetary volcanic activity and an increase in sunspot occurrences.

“We suspected we would see the millennia of aridity during the mid-Holocene at Kirman Lake, but we were surprised to see a very clear record of the medieval climate anomaly as well,” says MacDonald.

The problem, says MacDonald, is that whether the cause is the planet’s orbit, volcanic activity or, as is the case in the current scenario, the greenhouse effect, the consequences for California, its croplands and farmers is likely to be the same: drought which persists for decades at a time.

“We can’t save our huge expanses of oak woodlands, or our pine and fir forests, or high-elevation alpine ecosystems with irrigation projects like we might our orchards and gardens,” says MacDonald. “I worry that we will see very different wildlands by the end of this century.”

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