This tree survived the last ice age. Now it is threatened by development.

JURUPA VALLEY, CALIFORNIA — At first glance, one of the world's oldest living organisms doesn't look like much – a clump of shrubs nesting on a hillside in a rocky canyon. But those shrubs are just the crown of a giant, sprawling oak tree, 90 feet long and 30 feet wide. Most of the tree is underground.

The tree – known as the Jurupa oak – is estimated to be between 13,000 and 18,000 years old, making it older than almost any other plant on Earth. It has survived an ice age and rapid global warming, and its leaves may have grazed saber-toothed cats and 500-pound giant sloths. But now conservationists and locals fear the ancient tree is threatened by a force more commonplace in modern California: development.

The planning commission of Jurupa Valley, a city of 100,000 people an hour east of Los Angeles, is close to approving a 1.4-square-mile development that would include a business park, 1,700 apartments and an elementary school. Light industrial buildings would be located just a few hundred yards from the old tree.

The city believes the project will boost the local economy. The developer of the site has said he wants to protect the tree, but environmentalists say the construction and resulting development could be fatal to the Jurupa oak.

“It's unique among most things on the planet,” said Aaron Echols, conservation officer for the Riverside-San Bernardino chapter of the California Native Plant Society. “We have to be absolutely sure we're not harming this plant.”

The tree has plunged Jurupa Valley into an ongoing debate in California: How to balance the state's growth and need for housing with protecting its rich biodiversity.

When you think of the oldest tree in the world, you probably think of a bristlecone pine known as the “Methuselah,” which is estimated to be nearly 5,000 years old. The Jurupa oak falls into a different category: It is a Palmer oak, a type of “clonal tree,” a network of genetically identical shrubs connected by a common root system. Unlike normal trees, none of the original tissue remains; instead, after a forest fire, the tree sprouts new, genetically identical shoots from the burned stumps.

The tree we see today has evolved from this ancient root system. Most of the oldest plants in the world, like the Jurupa oak, are clone organisms.

“It's kind of a philosophical question,” says Jeffrey Ross-Ibarra, a professor of evolution and ecology at the University of California, Davis, about the difference between clone trees and traditional trees. “If I have a tree in my yard, I cut it down and a trunk grows back, I would generally think it's the same tree. But if you do that 10,000 times in a row, is it still the same tree?”

The oak was planted in the 1990s by local botanist Mitch Provance – but it wasn't until 2009 that researchers at UC-Davis, including Ross-Ibarra, calculated its immense age. It is now estimated to be the third or fourth oldest organism in the world. Its rivals include an American aspen in Utah, estimated at 80,000 years old, and a holly in Tasmania, estimated at 43,000 years old.

The tree could not have been found in a more unlikely location, clinging to a rocky ridge overlooking warehouses, horse trails and the tracks of off-road vehicle riders. Jurupa Valley is also not exactly known for its environmental quality: the city is best known nationwide for a series of polluted acid pits that made headlines in the 1980s.

The Jurupa Valley Planning Commission has not yet decided whether the project can proceed. At a meeting in late June, dozens of residents came to comment on the project — more than half called for it to be rejected or modified. The city also received more than 100 emails railing against the project.

“We have discovered a treasure on the world stage here in our humble town,” said Jenny Iyer, a Jurupa Valley resident. “Is one of the oldest living things on the planet going to die just because Jurupa Valley approves industrial and business parks nearby?”

One cause for concern is that the Jurupa oak grows far outside its normal zone. While the Jurupa Valley area was dotted with Palmer oaks during the last ice age, today they are all gone except for this one. Somehow the tree survives in conditions that should be too hot and too dry.

“It's already past its ecological extreme,” Echols said. “It's the only one out here.”

Local scientists and conservationists believe there may be a special microclimate or some kind of underground basin that provides the tree with extra water. However, the scientific analysis of the risks to the tree has not been made public – the planning commission in charge of the project says it cannot release the analysis because it would reveal the tree's location. (The Jurupa oak is considered a sacred site to indigenous peoples, but locals know its location.)

Tim Krantz, conservation director of the Wildlands Conservancy and professor emeritus at the University of Redlands, believes the tree is fed by groundwater seeping down from nearby hills. If those hills are covered with asphalt and concrete, he warns, the groundwater flow would stop – and the tree could die.

Developer Richland Communities counters that the plan will protect the tree through a number of strategies. The developer has promised not to build closer than 200 feet to the tree and to keep construction equipment 259 feet from the tree's edge. The company has also promised to donate the land immediately surrounding the tree to a nonprofit and provide a $250,000 endowment to protect it.

“Not approving the project does not protect the tree,” Jeremy Krout, a representative of Richland Communities, said at the meeting. “If the project is not approved, there is no protection; there is no responsible party protecting the tree.”

Richland Communities did not respond to a request for comment.

But environmentalists say a 200-foot shelter is far from enough to protect the oak. They argue that a light industrial building near the oak could lead to excessive car traffic and an urban heat island of cement and asphalt that could harm the tree.

Jim Pechous, Jurupa Valley's chief planner, said in an email that the city is considering creating a larger buffer zone around the tree and will study the oak's root system more closely.

At the meeting in late June, planning commissioners seemed baffled that they and their small town were being pushed into a decision about one of the oldest organisms on Earth. They listened carefully to environmentalists urging them to reject the development and to representatives of local plumbers and construction unions urging them to approve the project.

“It's really unbelievable that we have this treasure that is not being protected,” said Arleen Pruitt, acting chair of the Planning Commission, at one point at Jurupa Oak.

Commissioners ultimately voted to postpone the decision until July 10, when they will vote on whether to approve the plan — and then submit it to the City Council for a vote — or reject it.

On a recent afternoon, the tree stood in 90-degree heat, overlooking a small residential neighborhood and, in the distance, rows and rows of white-roofed warehouses. Krantz of the Wildlands Conservancy pointed to small acorns growing on the oak and piles of pollen.

“It represents endurance and resilience,” Krantz said of the oak. “It has survived fire and drought and ultimately climate change. And yet, despite everything, it is here – just like the poor people of Jurupa Valley.”

He touched one of the tiny acorns. “I'm just trying to get by,” he added.