A large portion of California’s crops might be in danger in the near future as a result of global climate change.
A recently released study states that the number of chilling hours required for the production of orchards in the Central Valley has decreased 30 percent since 1950. It also states that plants that are dormant in the winter do not grow as well with fewer chilling hours.
“Winter chill is decreasing and will decrease further because temperatures are rising,” said Eike Luedeling, lead author of the study. “By the end of the 21st century many species might have a hard time surviving [in the Central Valley]”.
Only 4 percent of the Central Valley is now suitable for apples, cherries and pears, all high-chill fruits that could once be grown in half the valley, according to the study. Large areas with winter chill may soon completely disappear.
The current study from UC Davis compliments another study done by scientists Dennis Baldocchi and Simon Wong of UC Berkeley. According to Luedeling, they surveyed hourly data from networks of weather stations throughout California to calculate chilling hours.
“Our results are similar,” Luedeling said. “The difference is our study is more sophisticated because we used a different model to calculate the chilling hours.“
To plant their crops, farmers calculate the number of hours the temperature drops below 45 degrees Fahrenheit. Luedeling and his team followed that standard, and used the Dynamic Model to measure a wider range of temperatures.
However, according to Luedeling, farmers can adapt to the differences in chilling hours by employing different plant breeding techniques and using chemicals that can influence micro-climates.
Despite the similar results from UC Davis‘ and UC Berkeley’s studies, some people disagree with the results and what it means for the Central Valley crops.
“These chill models are so unsophisticated,” said Steve Southwick, a former UC Davis fruit science professor who now works for OG Packing, a major cherry and walnut distributor. “The way a tree behaves doesn’t much match what the models say, and the level of research on fruit trees is meager.“
As of right now, there hasn’t been too much preparation for the decrease in chilling hours, Luedeling said.
“What is at stake here for global climate change is our food security and that is what we need to focus on,” he said.
CORY BULLIS can be reached at email@example.com.