One of Earth's oldest known plants takes center stage in California development battle

Compared to rugged California live oaks, the Palmer oak looks more like a shrub and is made up of individual stems sprouting in a grove. It wasn’t until fairly recently that researchers determined its impressive age.

Mitchell Provance, a botanist and associate researcher at the University of California, Riverside, first noticed the oak more than two decades ago and found it odd that it lived isolated from other members of its species in an area that was much lower and hotter than where the trees usually grow. He began discussing the tree with his colleagues. They hypothesized that it was the last holdout from a time when the region was cooler and wetter — a much friendlier environment for the oaks.

To see if this was the case, the researchers collected samples from multiple dead stems —and, sure enough, they all had identical DNA. Whenever the tree was damaged by a fire, it would resprout from the base of its trunk. By using tree rings to estimate how much the trunk can grow in a year, the team was able to calculate the tree’s age by measuring the grove’s diameter.

Today, the grove measures 80 feet wide, which led researchers to estimate that the tree is between 13,000 and 18,000 years old. It’s possible that the tree has been able to reproduce with itself, instead of just resprouting from the trunk to produce clones, but this is unlikely, experts say.

While the company has worked with the environmental consultant FirstCarbon Solutions to study the impact of construction vibrations on the tree and identify potential water sources, it has not mapped the tree’s root system or confirmed its direct water source — a process that would involve chemical testing of water at the oak’s roots.

Some also worry the proposed development would expose the aged oak to the urban heat island effect — a phenomenon in which developed areas can run 1 to 7 degrees higher than shaded, natural areas during the day.

Aaron Echols, the conservation chair of the Riverside/San Bernardino California Native Plants Society, said it was the duty of conservation groups to point out potential effects on the tree that haven’t yet been studied. “The burden to mitigate impacts … that’s on the applicant and the consultant.”

The portion of the environmental impact review discussing the Palmer oak — including its exact location — has been redacted from public documents. The city was required to do this by law, since the tree has sensitive cultural significance to the Native tribes. Consequently, independent scientists have been unable to scrutinize the report.

The city said it would explore “creative ways” to legally allow a select few third-party experts to view and discuss the report.