The first comprehensive survey of Palo Alto's venerable oaks in 20 years kicks off on Saturday, with help from neighborhood residents and volunteers in gathering data on the native trees.

The citywide tree count looks for native oaks of four species, where they are located and general condition. Conducted by the nonprofit tree organization Canopy, the survey is updating the original OakWell Survey, which Canopy conducted from 1997 to 2001. The data will help scientists evaluate ecosystem changes.

The information will also help Canopy with a program to replace native oaks lost in the last few decades. That program, "Re-Oaking Palo Alto," seeks to re-create a landscape closer to the historic landscape, said Elise Willis, Canopy's community forestry program manager.

Native oaks are valuable in the residential landscape, benefiting wildlife and people, Willis said. For wildlife, and plant species such as lichens, the oaks are a species on which other living creatures in an ecosystem largely depend.

In a single year, an oak can provide habitat for more than 300 species of vertebrates, 370 fungal species and almost 5,000 insect species, according to a 2017 report, "Re-Oaking Silicon Valley: Building Vibrant Cities with Nature," by the San Francisco Estuary Institute & The Aquatic Science Center.

For humans, the oak's broad, dense canopy provides shade to prevent "heat islands" created by pavement.

"As they mature, their functioning in terms of air quality improves by absorbing carbon, which is stored in wood, and they can capture more rainwater," Willis said of large, older trees. Mature oaks also increase property values, she said.

The trees live longer than many non-native trees; some have lifespans 250 years or longer in the urban environment. Coast live oaks grow faster and live in the 150- to 200-year range; valley oaks are slower growing at first and can live 250 to 300 years in an urban setting and up to 600 years in open space, Willis noted.

Poorly adapted non-native species live 50 to 75 years, and many in Palo Alto are reaching that end now, she said.

Oaks are one of two tree species the city targeted for protection in its tree ordinance, along with redwoods. Palo Alto recently adopted an Urban Forest Master Plan, which addresses conserving and enhancing the native tree population.

As part of the OakWell Survey, the nonprofit's first oak count, volunteers distributed door hangers to homes with native oak-care information.

"We saw there were a lot of folks moving here who didn't know how to care for the trees to help them survive," she said.

Some people were watering the oaks at the base in the summertime when the trees need to remain dry. The oaks do not do well and can be susceptible to diseases from overwatering, unlike eastern tree species that have adapted to summer months of periodic rain.

The Great Oak Count will also use door hangers to increase residents' awareness, but Canopy hopes technology that wasn't available 20 years ago will help researchers gain more insight into the city's oak denizens. The program will use Tree Plotter, a cloud-based mapping software that volunteers use to add or update data. Residents will be able to add information to the database about their oaks, Willis said. The last count took four years to complete, but with web-based technology, Willis said she hopes the survey could be completed in as little as two years.

A pilot survey will be held in College Terrace on Saturday from 9 a.m. to noon at Mayfield Park, 2300 Wellesley St. A larger roll-out to other neighborhoods will begin after Canopy refines the pilot program, Willis said.

As the city plans its future, Palo Alto will also need to look at "environmental resilience." Having a robust oak population in the urban forest "will offer a better chance to set us up to combat climate change," she said.

"In the Midpeninsula, if we are going to invest in our urban forest's future, we need to invest in our native oaks."

More information about Canopy's Great Oak Count can be found at canopy.org. Volunteers can contact Elise Willis at elise@canopy.org. Information about oaks can be found at Canopy's blog on its website.