The Sierra Nevada’s blue oak trees can tell many historical facts of the region, however the one scientist are focusing on is the amount of snowfall California has seen in the past 500 years. They have developed a method of measuring moister accumulation based on the blue oaks tree rings, and despite the current drought, the outcome of the study came as a surprise to the paleoclimatologist Valerie Trouet. “We expected (the results) to be bad, but we certainly didn’t expect it to be the worst in the past 500 years.”

To determine the result, the research team developed a model where the combination of two data sets of blue oak tree rings showed historical precipitation levels from more than 1,500 trees. By tracing a time frame and comparing the data, they came to the conclusion that the winter of 2015 was the driest in the 500 year spam.

When winter comes to California, these trees utilize the moisture stored in the soil to grow, therefore the width of their rings reflect the amount of precipitation from that season. The wider the ring, the wetter the winter.

This comes to show how we are migrating into a different world – one where temperatures are higher and there is a decline in precipitation. We have to adapt to the changes around us. A decrease in snowpack will automatic result in lower levels of water in California’s reservoirs. Even though El Niño is promising a rainy season, will the blue oaks in the Sierra Nevada tell a different story come winter 2016?

Read more about the importance of California’s snowpack here.