The Nature Reserve at Rancho Mission Viejo marks 20 years of preservation among development
Mother Oak, as she's known, stands tall over the rest of the younger California coast live oak trees sprouting from the ground in this vast expanse of untouched land, a landmark thought to be more than 500 years old set within The Nature Reserve at Rancho Mission Viejo.
Following storms, creeks meander through the land, offering wildlife a drink from the freshwater before it spills downstream. Only a few hints of human presence exist, including a gathering area where schoolchildren marvel at outdoor nature lessons, a wooden bridge built by a Boy Scout group years ago and a spinning windmill that still pumps water through a trough for thirsty cattle living on the ranch.
"Welcome to Old California," declared Laura Coley Eisenberg, senior vice president of open space management at Rancho Mission Viejo, her arms spread out in a valley that sits just a few short miles from homes, busy streets and highways filled with humans going about their day.
Rancho Mission Viejo is one of the last remaining puzzle pieces for developing Orange County, and its combination of development and conservation is a legacy of a family that has shaped what South OC has, and will, become.
This year marks the 20th anniversary since plans were approved for Rancho Mission Viejo, made up of 25% development and 75% preserved land.
It’s a formula based on a simple sentiment, the community’s developers say, carried on through generations of the family tasked with caring for the future of the large swath of land: "Take care of the land and the land will take care of you."
A deal between friends
It was a handshake deal between two fellow Irish immigrants, James Flood and Richard O'Neill, that would set south Orange County's future, the stories go.
It was the late 1800s, and the Army was sent to California to establish a greater presence to quell concerns about Russians in the Pacific Northwest following the purchase of Alaska, and Mexico to the south wanting to reclaim the state.
The Army needed to be fed, and O'Neill was an established cattleman who owned a meat market in San Francisco. And his friend Flood had the capital to fund the operation.
They became partners owning about 200,000 acres of Rancho Santa Margarita Las Flores, starting at the foot of the Saddleback Mountain and spanning down to Oceanside in a sale that cost $250,000, said Jeremy Laster, president of Rancho Mission Viejo and one of the remaining family members tasked with day-to-day operations.
The Department of the Navy in 1942 used the War Powers Act to purchase Flood’s San Diego portion, about 150,000 acres, today’s Camp Pendleton.
The remaining 52,000 acres stayed with Richard O'Neill Jr.; his wife, Marguerite; and their two children, Alice and Richard Jerome. After O’Neill Jr. died in 1944, Marguerite, known as "Daisy," took over operations, and later their son, also Richard O’Neill, who died in 2009 at age 85.
Through the years, others have tried to purchase the land. Stories that famed gangster Al Capone was interested in using it as a smuggling route during Prohibition add to its lore, and even Irvine developer Donald Bren, who worked for the company early in his career, has reportedly tried to buy parts of the property.
"It's a point of pride that they never sold," Laster said.
Unlike much of Orange County, broken up into small parcels by landowners and sold off to investors, family members kept control of the land.
The family tree that works at the company is extensive: Tony Moiso, the O’Neills’ nephew, is chairman and CEO of Rancho Mission Viejo, and Laster is his son-in-law. Family members also include Trina Moiso Lamkin and her husband, Marc Lamkin, both vice presidents.
By the 1960s, as populations boomed, the O'Neill family and partners built the 10,000-acre planned community of Mission Viejo and went on to develop other communities: Rancho Santa Margarita, Las Flores and Ladera Ranch.
Through the years, the family also donated to the county parts of the ranch land to be park and open space, including for O'Neill Regional Park, Riley Wilderness Park and Caspers Wilderness Park.
But it's not necessarily easy to give away “free” land.
The county stopped accepting land unless there was a financial commitment to help care for it, add security and include other measures to protect it.
So instead of donating more land, the company in the early 2000s started creating a framework to set aside open space with its own land-use management and open space preservation plans.
Connect, preserve and explore
On a recent day, Coley Eisenberg pointed out a unique "peek-a-boo tree," a large sycamore with a hole through the trunk, an old injury the tree grew around.
"It's kind of fun; you work at a place for so long, you get to know certain trees," she said, but also, “you can run down a canyon, and there's always something new to see. There's always cool surprises."
She's gotten to know The Nature Reserve well, tasked 26 years ago with mapping out its 20,868 acres of land and working with permitting agencies to find the right mix of open space and development.
She spent years cataloguing which species called the land home, mapping sensitive areas, so the developers could figure out where to put homes in areas that would have the least impact during the entitlement process. Plans were refined, acres were eliminated and development consolidated, she said.
"Everyone talks about sustainability, or people against development at all. But we also have to provide housing, much-needed housing here in California and the broader United States," Coley Eisenberg said. "So if you provide a plan where you can do both, you provide for much-needed housing and supporting infrastructure, plus you preserve most of the area and open space. To me, that is sustainable."
The entitlement allowed 14,000 homes to be developed, all on the northwest slice of the ranch. About half of the planned neighborhood developments are complete.
"It's a very thoughtful plan,” Laster said. “We didn't spread the units all over the place and destroy all the habitat and landscape.”
Everything south and east of Ortega Highway won't be developed, he noted.
Even in developed areas, considerations were made, such as including "wildlife exclusion fencing" near roads to reduce incidents of wildlife mortality, Coley Eisenberg said.
"You definitely can do development in a very sensitive manner, beginning with deciding where to do it," she said.
Every five years, a remapping of the entire reserve is done to evaluate the habitat, she said, part of a management and monitoring plan to detect change. And, each year, various studies are done to determine the health of plant life and animals.
High-tech imagery taken from above is used to document light that goes through the tree canopies - the less light hitting the ground, the healthier the tree, Coley Eisenberg explained.
Mother Oak, for example, has been on the decline as the tree ages. But smaller oaks around her will grow to replace her when she topples over, Coley Eisenberg said.
"They don't live forever," she said.
This year, Coley Eisenberg and her team will be studying riparian birds to make sure populations are thriving. They had hoped to survey the arroyo toad population as well, but the recent dry spell may curb those plans.
"There's always something going on, every year," she said.
One big concern recently has been an invasive beetle, the goldspotted oak borer, that has infested 60% of the oak trees across nearby San Diego County. If the beetle does make its way into the preserve, Coley Eisenberg said specialized trunk injection and washes will be used to prevent its destructive spread.
The beetle mostly travels with firewood burning, so that's one of the benefits of keeping the land private - human impacts can be minimized.
"Primarily, the reserve is here for the species," Coley Eisenberg said. "We're trying to balance access for people … but also making sure the birds and animals can breed and continue to exist."
In parts of the former ranch, cattle still graze to get rid of invasive plants, and an orchard grows avocados and citrus.
Laster speaks highly of Moiso's leadership in ensuring that The Nature Reserve has an endowment to pay for the monitoring and maintenance of the land, as well as the field trips to introduce thousands of kids to the wild each year.
The balance of giving just the right amount of public access is an internal struggle they are consistently facing, Laster said.
"We don't want to have a fence around it and tell people to look inside," he said.
The Nature Reserve offers open access days to designated areas for recreation hikes, led by docents and guides, or meet-ups with local wildlife groups.
Coming up, there's everything from an astronomy night to family nature walks, and there are trail stewardship opportunities for those who don't mind getting their hands dirty. Residents of Rancho Mission Viejo get added perks of community meet-ups and tours.
"In just five minutes, you can see deer and coyotes and bobcats; they are all in our backyard," Laster said.
On any given weekday, dozens of schoolchildren are brought out to learn about nature at the Richard and Donna O'Neill Conservancy.
During a recent field trip, a volunteer explained to a group of students how glaciers form and melt, creating valleys, such as Yosemite, or how storms bring water down mountains to create rivers.
The idea is to "connect, preserve and explore," Coley Eisenberg said.
"One thing we really strive for is to make connections with kids when they are young. Because if you don't know what nature is about, you perhaps won't care about it so much later," Coley Eisenberg said. "So we can start out really young and hopefully capture their attention and keep it."
Go to thenaturereserve.org to see upcoming events and public access days; there is also information on how to request a field trip.
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This story was originally published April 20, 2026 at 7:21 AM.