Tree mortality expected to climb from 2015
VALLEJO, California – With tree mortality rising to an estimated record-high 27.6 million trees in California in 2015, the U.S. Forest Service Aerial Survey team’s role in generating data for the agency and state and local partners is more critical than ever.
The U.S. Forest Service began doing aerial survey detection in the Pacific Northwest Region in the 1950s, with a small program in the Pacific Southwest Region (California) established in the 1990s. A dedicated team was assigned to the regional office in the early 2000s when Sudden Oak Death became more prevalent. In addition to detecting the Sudden Oak Death and conifer mortality, aerial survey flights first detected the Gold Spotted Oak Borer infestation in 2004.
Last year, Aerial Survey Program Manager Jeffrey Moore and his team discovered nearly 10 times more dead trees than the previously recorded high of 3.3 million in 2014.
Despite a limited budget and a short timeframe, the team employs a Cessna 205 aircraft flying at 120 miles per hour using a three-mile grid pattern to approach a fairly thorough albeit rapid coverage of the landscape. Inside the cockpit, surveyors make freehand sketches on GPS referenced computer touch tablets using the measurements of a football field to give them a base for an acre of land. A top-down oblique viewing angle allows surveyors to differentiate between species of trees. Color and texture also play a major role in, for example, determining a coulter pine from a sugar pine. With over 150 flights per year from June through September, Moore and an additional surveyor piece together what they see on the landscape.
Weather and smoke can cause safety and visibility concerns, so it is critical that surveys are conducted when the conditions are ideal. “We need direct sun off of the tree canopy,” said Moore. “We’re looking at which trees have changed color from green to red or yellow.”
Once back in the office, the data is analyzed and succinctly summarized using Geographic Information System software and cartographic satellite imagery for the background.
The aerial survey information is also used for forest planning to include prioritizing timber harvesting. Additionally, this regional data is incorporated into a national database along with other regions/programs across the country.
“I like to think of it as doing an annual checkup of forests for the whole state,” said Moore. “Getting that pulse, reading the vital signs and assessing the severity of ailments and the general health overall. It is also good for historical purposes to see the trends over time. There are a lot of theories out there and this helps to check that and potentially reinforce, fine tune or cause us to rethink commonly held concepts.”
An early special stand-alone survey for the most impacted areas was planned for early April, but weather caused a cancellation. The first flight of the regular surveys is expected to be made in early June with the last one wrapping up in early September.