California's devastating drought of 2012-2016 caused widespread tree loss and the death of many species. The first study published in Frontiers in Climate, an open access journal, shows that California's blue oak (Quercus douglasii), woodlands has also declined by more than 1,200km. Another metric that measures the alteration or deterioration of the tree cover shows that the blue oak range lost more than 600 km2. These results highlight the importance of raising awareness about the vulnerability these ecosystems, and adapting conservation strategies to rising climate extremes.
"Our findings suggest that droughts that last several decades, and which occur alongside warmer than historical normal temperatures, pose serious risks to the blue oak forests," Dr Francis Dwomoh (ASRC Federal Data Solutions), first author. He is a contractor for the US Geological Survey Earth Resources Observation and Science Center. These extreme climatic conditions, when combined with wildfires can lead to significant tree loss. This could have negative consequences for wildlife and plants as well as the goods or services that we derive from the ecosystem.
California is the only state where blue oak woodlands can be found. They are the last remaining remnants of pre-European settlement native old-growth forests (pre-European settlement) in the area. This ecosystem is also home to over 300 species of vertebrate animals. It is one of California's most biodiverse.
The research team developed new models of land change using the extensive Landsat satellite series record to better understand the ecosystem's response to climate warming and related disturbances like wildfires. Conditional change, which is a partial disruption or degrading of woodlands, indicates their health, productivity, and susceptibility to future disturbances. However, past studies did not have the ability to distinguish between these states.
Even without fires, significant woodland destruction
The new data from the U.S. Geological Survey Land Change Monitoring, Assessment and Projection project (LCMAP) was combined with records of climate and wildfires for the period 1985 - 2016. They discovered that 2012-2016 drought was related to tree cover loss and conditions changing with or without forest fires. It was not surprising that fire loss was especially high in the hottest and driest years.
These results are based upon satellite measurements and models. Fieldwork would give a better picture of the condition of these forests. This approach along with the LCMAP data for 48 US states may be useful for monitoring future changes as well as developing conservation strategies in California.
Dwomoh says, "We hope that the research findings will be helpful in identifying and prioritizing most vulnerable areas of woodlands for the appropriate management interventions." "Our results may also be useful in planning for blue oak woodlands that are more resilient and similar landscapes, as the harsher climate conditions of 2012-2016 will likely to become more frequent in the future."