In California, residents may experience the driest year in the last half millennium, according to scientists. The past 12 months have been the driest on record in the state, following two below-normal years. The situation is so extreme that it prompted Gov. Jerry Brown to declare a drought emergency earlier this month.

In an op-ed for the Los Angeles Times, professor of earth and planetary science at UC Berkeley, B. Lynn Ingram and biologist and senior environmental planner with the California Department of Transportation, Frances Malamud-Roam, discuss California’s current state. California’s reliance on winter storms for the majority of their water supply means that the state has received no significant water in more than a year.

The scientists examined how California’s current drought compares with the climate history of the state. Looking back even further than the 119 years on record, scientists believe AD 1580 was the driest year in the last 500 years, based on the growth rings of trees. Evidence shows that the giant sequoias failed to grow at all that year.

The second driest year was 1976-77, when precipitation was 15 percent of average, reservoirs were one-third of their normal levels, and 7.5 million trees weaken by drought died of insect-related diseases and fueled massive wildfires. According to Ingram and Malamud-Roam, the 2014 water year, which began on October 1, is on track to be drier than the drought of 1976-77.

Over two decades ago, scientists noted that if greenhouse gas emissions continued to increase rapidly, severe drought would also increase substantially. Based on the patterns of the past several thousand years, Ingram and Malamud-Roam say that “we can expect more and longer droughts than what we have seen in the last 119 years.”

This is an issue for California’s “rapidly growing population and enormous agricultural industry.” But it is also an issue for the rest of the United States. According to a California website, the state produces half of the nation’s fruits, vegetables, and nuts, and is the nation’s number-one dairy state.

“The climate clock is ticking,” Ingram and Malamud-Roam conclude. “And it is time for policymakers in the West to prepare for a warmer and drier future facing the region.”

Gov. Brown has encouraged residents to voluntarily reduce their water usage, but said his administration is considering a mandatory conservation order. “I think the drought emphasizes that we do live in an era of limits, that nature has its boundaries,” he said during his formal proclamation of a drought emergency this month.

Other western states are also experiencing extreme droughts. Earlier this month, the Department of Agriculture announced that counties in Colorado, New Mexico, Nevada, Kansas, Texas, Utah, Arkansas, Hawaii, Idaho, Oklahoma, and California would be designated primary natural disaster areas, The Guardian reports. This designation will allow eligible farmers to qualify for emergency loans from the department.

The oil and gas boom is also straining many dry states’ water supplies. Fracking is depleting some of the driest, most drought-prone states of water and is competing for usage of states’ fresh water supplies. Oil-rich states such as Texas, Colorado, and Pennsylvania are particularly at risk. A report released this month indicates that, since 2011, more than half of hydraulically fractured wells have been located in areas experiencing drought.

Alisha is a writer and researcher with Ring of Fire. You can follow her on Twitter @childoftheearth.