A Redwood Is A Community, Not Only A Tree

More people are likely to have reached the summit of Mount Everest than have been to the top of an old-growth redwood tree, which helps explain why we know little about the biodiversity these giants harbor.

Now, scientists are conducting a top-to-bottom inventory of all the plants, mosses, lichens and more living in and on the trees. To their surprise, they found branches, leaves and trunks teeming with life, in some cases tallying more than 100 species for a single redwood.

“It is, of course, extremely awesome that redwoods themselves are so enormous and old, but the fact that they support entire miniature communities of so many other species is mind-boggling,” said Rikke Reese Næsborg, a lichenologist associated with the University of California, Berkeley. “There are many, many more species up there than people originally thought.”

Coast redwoods are not the world’s largest trees — that title belongs to their inland cousin, the giant sequoia — but they are the tallest, reaching up to 379 feet high. Were such a redwood to sprout on Liberty Island, it might eventually reach higher than the Statue of Liberty’s extended torch. But growing that tall also takes time — the oldest coast redwood is an estimated 2,200 years old.

Despite these impressive statistics, the fact that redwoods are home to so many additional species intrigued Dr. Næsborg and her husband, Cameron Williams, a doctoral candidate at the University of California, Berkeley, who met Dr. Næsborg over a decade ago at a lichen conference in Estonia. The researchers had suspected that the redwoods’ rosy colored namesake tannins would deter communities from forming in the trees, because many organisms do find those chemicals unpalatable.

Mr. Williams was the first to try to identify all the players involved in those communities. He focused on epiphytes (literally “on plant”), or species that grow on trees without harming them, like mosses, lichens and other vegetation. Ascending redwoods in northwestern California, he found trunks wrapped in blankets of fuzzy, grass-green moss; twigs covered by whimsical chartreuse lichen wisps; and in places where they could eke out a precarious roothold, a variety of saplings and bushes — currant, huckleberry, hemlock and more — some of which had epiphytic communities of their own. All told, the survey found that redwoods contain more diversity — 282 epiphytes in and directly beneath the trees — than other tree species that researchers had previously sampled, including the Douglas fir and the Sitka spruce. This study also uncovered a species new to science — a lichen as diminutive as its redwood host is towering. Sprouting from the tree bark like a minuscule hair, Mr. Williams bestowed it with a fitting name: redwood stubble.

The research would most likely have ended there if not for Save the Redwoods League, a nonprofit group that promotes protection of redwoods. The league asked the researchers to conduct an epiphyte survey of redwood communities at the southern end of the tree range. Preliminary results of that study reveal patterns of diversity — 237 species so far — similar to those found in the north.

In both the north and south, from Jedediah Smith Redwoods State Park to Pfeiffer Big Sur State Park, lichens — science-fiction-like organisms that exist as symbiotic assemblies of fungi and algae or cyanobacteria — make up most of the species identified. About 17,000 lichen species are known worldwide, although much about them remains unknown — for example, the potential uses for the more than 600 unique compounds that lichens are known to produce. Some of them are already being used today as antibiotics in soaps and deodorants, and others as ingredients in traditional treatments for constipation, arthritis and kidney diseases; others still are being investigated as cancer-fighting agents.

Indeed, climbing was crucial for the researchers’ discoveries: Just 33 percent of the lichen diversity they found was on the ground. But viewing the vibrant communities firsthand involves more than getting there. Almost all old-growth redwoods are in parks and reserves where climbing the trees is prohibited; even scientists can have trouble obtaining the necessary permits.

In Mr. Williams’s case, that involved submitting a detailed proposal to California State Park authorities, who sent it to other canopy researchers to assess its validity and also ask about his ability to climb safely and gently, as well as undergoing long interviews both by phone and in the field.

Once a year, over a few weekends in March, an exception is made, allowing nonscientists to experience what it’s like at the top of a roughly 800-year-old redwood known as Grandfather, on private property near Los Gatos, Calif. The annual event is organized by Tim Kovar, a master instructor who regularly arranges excursions.

“I love educating people, getting them interested in science and what’s going on in the treetops — a place right above our heads but usually out of reach,” Mr. Kovar said. He also assists canopy scientists around the world with data collection and tree-climbing techniques. “The knowledge that comes from hanging with scientists is a gift,” Mr. Kovar said.

On Easter Sunday, Mr. Kovar, Mr. Williams and Dr. Næsborg outfitted four novice climbers, including me, with saddles. Fashioned a bit like diapers, they would support us as we made our way up and down the tree using two pieces of gear, an ascender and a descender. After a brief demonstration and a practice run, we clipped onto ropes hanging from Grandfather’s branches, which Mr. Kovar had rigged using a crossbow.

While there are several methods for ascending, we used the so-called Texas style, a sit-stand-sit-stand technique often employed by researchers. Slowly, we began inch-worming our way up, passing bird nests and woodpecker holes, splotches of lichen and scars of long-ago lightning strikes. Although no data were being collected, Mr. Williams schooled us on the history of redwoods. As the ground slowly receded, his words grew a bit distant as I felt my chest constrict and mouth go dry. Although Mr. Kovar had never had an accident, we were dizzyingly high. The experts’ cool demeanor kept me grounded, however. As Mr. Kovar said, “Enjoy this tree time.”

An hour and a half later, we finally broke through the shadows into the canopy, stopping just shy of Grandfather’s 200-foot summit. Gazing out at a haze of treetops bathed in the late afternoon sun, I was reminded of Bilbo Baggins’s view of Mirkwood Forest in “The Hobbit” — a tiny figure lost among giants. Still, the forest was nothing like it used to be. Before the 1700s, redwoods covered around two million acres from southwestern Oregon to Big Sur, Calif. Logging and development have reduced the old-growth trees to just 120,000 acres.

Mr. Williams finally broke our contemplative silence.

“I think the best outcome of these guided climbs is that most participants are humbled,” he said. “If more people were able to climb among the branches of such an immense living organism, I believe we’d have better conservation values as a whole.”