Once upon a time, the Napa Valley was dotted with oak forests, and several conservation-focused organizations are seeking volunteers to help repopulate the area with these trees, organizers said.

A Coastal Conservancy grant was awarded for the Napa County Recourse Conservation District, Friends of the Napa River, California State Coastal Conservancy, City of Napa, City of American Canyon’s — “5,000 Oaks Initiative.” This seeks, as the name implies, to plant 5,000 native oaks across Napa County in the next three years,” organizer Eric McKee said. An acorn planting event is planned for 11 a.m. to 2 p.m. Saturday, Nov. 7 in American Canyon’s Newell Open Space as part of this effort, he said.

“This is the first one we’re doing,” he said. “The Resource Conservation District, which works to improve watershed health throughout Napa County, did a historical ecology study on what the area was like before the arrival of the Europeans, and they found there’s been a big conversion of our land; we’ve lost some 37,000 acres of oak woodland forest, which was reduced to less than 150 acres.”

Most of those trees were lost to agriculture and urban development between the 1800s and 2010, he said.

In American Canyon specifically, which is about at sea level, these trees can help the area adapt to changing climates, he said.

“Before the early 1800s this area — including Napa, American Canyon and also likely parts of Vallejo, were oak forests,” McKee said. “We’re looking at those areas and trying to replant oak trees to those areas where that’s feasible — around schools, parks, ranches and vineyards, and we’re encouraging people to plant them in their yards.”

The valley oak in particular is a keystone species providing “a high amount of habitat, food and nesting sources and other ecosystem services for animal life,” McKee said. “It’s a really critical tree species, providing erosion control, carbon sequestration or storage, and supporting a high amount of biodiversity — many type of species — which is what makes a watershed healthy.”

The danger in losing these trees is implied in the ecological services they provide, he said.

“The air that is less clean, there’s increased erosion, less biodiversity, fewer recreation opportunities, less energy savings, since these trees are shade providers for cattle and people. We’ve lost a lot of that,” McKee said.

There are early accounts — including the following from “Napa Valley Historical Ecology Atlas: Exploring A Hidden Landscape of Transformation and Resilience” — of people describing the rolling hills around American Canyon containing large stands of oak trees, he said.

A few trees were planted last week with help from American Canyon High School students and the number of trees that will be planted on Nov. 7 will depend on the how man volunteers show up, McKee said. There is no minimum or maximum age limit for volunteers, he said.

The trees will be planted from seeds, aka acorns, he said.

“They germinate in a few months, so, by April or so, there should be some shoots,” he said. “They grow about a foot a year and can live 500 years or more.”

Oaks weren’t the only trees once plentiful locally, he said. There were also black walnut, California buckeye, black cottonwood, willow, alder, big leaf maple and other oak species, he said.

“Maybe one day we’ll go after planting some of those,” he said.

The study’s main lesson may be that “progress isn’t always good, at least not the for ecosystem,” McKee said.

“In the early days, things were used without regard to ecosystems and how they work,” he said. “We’ve gotten more efficient at using land, and as science has evolved, we’re finding it’s created problems we now have to find solutions to.”

The acorn planting event will begin with an easy guided hike, up to one mile, then the acorn planting and an opportunity to learn from docents about the local environment. All materials and instruction will be provided and a picnic lunch will follow.

Contact Rachel Raskin-Zrihen at (707) 553-6824.