It’s called the Los Angeles River, but it’s really a 51-mile stretch of concrete. In the 1930s, the US Army Corps of Engineers began lining the waterway to mitigate the risk of flooding in the burgeoning city.
Now work is underway to make the river more like what it once was. In a segment dubbed the Bowtie Package, scientists try to transform what was once a busy railroad yard into a place where life can flourish again and people can enjoy nature.
“The hardest part is seeing something that isn’t there, so you have to help make the invisible visible,” said Lewis MacAdams, a poet and activist for bringing nature back to the LA River before he passed away in 2020. He shared that idea with Kat Superfisky, an urban ecologist at the City of Los Angeles who works on the river.
But when so much of riverside life was long ago wiped out by concrete, how do you make the invisible visible? Part of the answer is to study organisms that have died in the past 60,000 years.
Along the LA River and in other parts of the world, the Earth’s fossil record contributes to the preservation and enhancement of natural landscapes. It’s part of a growing field called conservation paleobiology, which aims to use dead and buried life to help scientists like Ms. Superfisky achieve their goals.
The La Brea Tar Pits — natural pits of pitch-black tar that over the millennia have caught and buried things that lived in Southern California — are about eight miles west of the LA River.
Fossils found in the tar include everything from saber-toothed cats, giant ground sloths, dire wolves and grizzly bears to plants such as oaks and junipers.
The potholes are a far cry from the image of a pristine river. Nevertheless, they are windows to the life that once flourished in the region and can flourish there again.
Jessie George, who recently completed her Ph.D. from the University of California, Los Angeles, studies fossilized plants in the tar pits. While touring the site, she explained that fossils can reveal how past life fared during ancient periods of climate change. In our era of human-induced climate change, Dr. George, that is crucial information for work along the river.
“We have these different windows of different habitats from different times,” said Dr. George as she crouched over the tarred bones of a dire wolf and some juniper seeds. “We can see in real time how they respond to the climate.”
Juniper, for example, is native to Southern California. But according to the fossil record, the plant is not doing well in a warming world.
“Juniper is very sensitive to those periods of warming,” said Regan Dunn, a paleobotanist at the Tar Pits. “We’re looking at those intervals that are hottest, and junipers are dying off en masse in the Southwest.”
But the fossil record of oak trees — particularly a species called coastal live oak — tells a different story, of resilience in tumultuous times.
“It spans almost all of the record and has persisted across a wide range of environmental changes,” said Dr. George. “It has been related to repeated, short-term warming and cooling events.”
Such information is helpful to Sophie Parker, a scientist at The Nature Conservancy, who is leading the improvement of the Bowtie package with California State Parks. She can use it to determine which plants to turn to as the Bowtie work unfolds.
“We want to select plants that will survive and eventually be self-sufficient and able to reproduce,” said Dr. Parker, who noted that plants such as oaks can create nesting habitats for certain local birds.
“We plan to work with the folks at La Brea to see what kind of overlap there is between our concept plant palette and their list of plants in the paleo record,” said Dr. Parker.
In ways big and small, fossils can change the way we think about the natural world.
“Sometimes people just want to know if the species is native or not,” said Alexis Mychajliw, a professor at Middlebury College in Vermont who did her postdoctoral research at the tar pits. “That’s one of the simplest things the fossil record can be useful for.”
For example, coyotes roam Southern California and, according to Dr. Mychajliw seen by many as a nuisance.
But there are fossilized coyote skulls in the tar pits that date back many thousands of years.
“If you see it as an intruder, rather than seeing it as part of your home landscape, it might change the way you interact with the animal,” said Dr. Mychajliw. She added that for urbanites in a place like Los Angeles, “It’s really powerful to give people this vision of what their landscape looked like over time.”
Such fossil records are, in the hands of conservation paleobiologists around the world, adding ancient perspectives to modern conservation problems in a variety of environments.
Fossil records revealed an altered ecosystem in Mexico’s Colorado River Delta, where the Colorado River once emptied into the Pacific Ocean before being dammed. In 2014, the information helped to allow the river to briefly flow into the delta for the first time in years.
Shark conservation work in Panama is informed by the study of fossilized shark scales, which reveal how the cartilaginous fish have responded to human intervention over time.
Back in California, a memorial bust of Mr. MacAdams, the poet, stands at an entrance to a multi-purpose trail across the LA River from the Bowtie lot.
According to Ms. Superfisky, the river was once not even called a river, but was a “flood channel”. But, she explained, Mr. MacAdams would interject “river” whenever he heard “flood channel” at Los Angeles Department of Public Works meetings.
Steadily, the word “river” regained its currency.
Mr. MacAdams helped change the story around the river and what nature is, just as scientists who study fossils are doing now. It’s a task that Mr. MacAdams passed on to Ms. Superfisky when he died.
“You are the next wave of the movement,” she told her.