I'm standing inside one of the tallest trees in the world. The Sequoia sempervirens, or coast redwood tree, found only in Northern California can climb as high as 380 feet and live for 2,000 years. On this warm morning in May, I've ducked into an 8-foot-high cavity, called a basal hollow, created by fires repeatedly burning into the interior of this beauty. After a few hundred years or so, the fires may create a hollow big enough to fit a few people.

Let's just say it's not a typical Monday, even for a California native.

It's musty inside, and I'm certain a family of spiders is about to gleefully fall on my head. (Bats are a common basal hollow resident, but I don't see any today.) Still, it's awesome to be surrounded by one of the oldest and largest living things on Earth. The 400-year-old tree obscures a deep blue sky recently cleared of fog, and its thick girth feels impenetrable. If there's a better way of getting in touch with nature, I can't imagine it.

Two hundred years ago, you could have stood in a basal hollow almost anywhere on the northern California coast. Redwoods sprawled over 2.2 million acres from California's central coast to the Oregon border. But today, only 5%, or 113,000 acres, of those old-growth redwoods remain, the rest felled by loggers in the first 20 years after the California Gold Rush, which began in 1848. About 75% of the surviving ancient trees are protected on public lands, but the rest are scattered on isolated pockets of private property. Redwood logging is strictly controlled, but illegal cutting and pollution from marijuana cultivation are serious threats to their survival.

CNET producer Andy Altman stands in the basal hollow of a giant redwood tree. James Martin/CNET

It's those vulnerable trees that the San Francisco-based Save the Redwoods League works to protect. A year ago, the nonprofit took the biggest conservation step in its 100-year history when it purchased a pristine, 730-acre redwood grove 100 miles north of San Francisco. Packed with massive trees, the Harold Richardson Redwood Reserve includes not just the redwood I stood inside, but also one that dates to the middle of the fifth century, when the Roman Empire was disintegrating.

By 2023, the League plans to open the reserve to the public. But until then, it plans to study how to help the redwoods thrive and to use technology including microphones, cameras and drones to save endangered wildlife like the marbled murrelet seabird and the northern spotted owl, which live in these magnificent trees. By knowing where those creatures are on the property, the League can help ensure their survival.

Diamond in the rough

Sam Hodder, the president and CEO of the Save the Redwoods League, stands in the Roberts Regional Recreation Area, a park in the Oakland hills filled with second-growth redwoods. James Martin/CNET

The opportunity to buy the Harold Richardson Reserve was unprecedented, says Sam Hodder, president and CEO of Save The Redwoods League. "This is the largest unprotected coast redwood forest anywhere in the world. It's just extraordinary to think about how much of a diamond in the rough it is."

The fact the grove has remained unspoiled stems in part from its remote location. A few miles inland from the coastal hamlet of Stewarts Point on California's famed Highway 1 in Sonoma County, it's a slog of a drive -- about three hours north of San Francisco on winding, car-sickness-inducing roads that drop sharply on one side to the Pacific Ocean. The scenery is stunning, which is good, since you have plenty of time to enjoy it.

The trees in the grove also owe their longevity to the Richardsons, a timber and ranching family that acquired the land in the 1920s and now owns thousands of acres in the county. Though they've continually operated a logging business in the area, the Richardsons also valued the grove's ancient trees. Cutting younger trees elsewhere, they spared the oldest and tallest redwoods in the reserve, leaving it almost as it was before they arrived.

In 2010, the family began working with the League on redwood conservation, an effort that led to the 2018 sale (the League raised the $9.6 million purchase price through private donations). The grove now bears the name of Harold Richardson, the family patriarch who died in 2016.

This is the largest unprotected coast redwood forest anywhere in the world. Sam Hodder, Save the Redwoods League

With little money available in state or federal budgets for land purchases of that size, Hodder says the League had no other option but to step in. "When we had an opportunity to acquire an old-growth forest, we jumped at the chance," he says. "It was a truly unique opportunity to save a remnant of an ecosystem that had almost been extinct from the planet."

The reserve's entrance is on a country road across from a lumber mill that the Richardson family still operates. With just a metal gate at the end of a dirt turnout, it's an understated approach to what we're about to see. Though the reserve has 300 redwoods over 250 feet tall, it's impossible to spot them among the mass of trees in the valley below.

The League's Anthony Castaños holds a map of the Richardson reserve. The yellow dots show redwoods higher than 250 feet. Kent German/CNET

Anthony Castaños, a League land stewardship manager who's waiting to show us around, starts by describing why an old-growth forest is so critical to the local ecosystem, which includes over 373 species of plants and animals like the foothill yellow-legged frog, Townsend's big-eared bat, Pacific giant salamander, steelhead trout and coho salmon. "[This property] provides so much more to wildlife and carbon sequestration than a younger forest," he says. "So making sure that we can protect these trees is really vital for the longevity of some species."

The tallest and the oldest

One of those species is the marbled murrelet, a Pacific Ocean seabird. Murrelets spend most of their lives floating offshore, waiting to dive just below the ocean's surface for fish. But when they're ready to lay eggs, they nestle in the branches of only the tallest and oldest redwoods. There, high above the ground and protected from rain, sun and predators, the birds lay their eggs directly on the strong branches that extend horizontally from the trunk.

The McApin tree is the oldest and tallest redwood on the property. James Martin/CNET

The dense concentration of old trees makes it the perfect place to study the small black-and-white birds and how to preserve them, says Stephanie Martin, a wildlife biologist with North Coast Resource Management, an environmental consulting firm that contracts with the League. Though their range can extend from Alaska to Southern California, murrelets are now endangered, partially due to the disappearance of the old-growth redwoods they prefer.

"It's a matter of valuing our system and the way it stands," she says. "This particular seabird has always been known to nest only in large redwood trees, but those are few and far between."

Wildlife biologist Stephanie Martin removes the tree-mounted microphones that listen for the call of the marbled murrelet. James Martin/CNET

As we walk deeper into the forest, the air cools with only patches of sunlight reaching the ground. We pause near the 239-foot-tall McApin tree, named for a rancher who settled in the area in the 19th century. At 1,640 years old, it's the oldest redwood in the reserve, and it's as wide as a two-lane street. Martin smiles frequently as she describes the trees around us, making her excitement for the project palpable. She loves her work so much she commutes from her home in Maine to California every two weeks during the summer. Even the drive to the property from her firm's office in Ukiah -- almost two hours on a narrow road over the coastal mountains -- requires commitment.

Martin's study of the murrelets begins with the arduous job of finding them. Their small size and the little time they spend inland makes them elusive, so she uses six Song Meter SM4 Recorders strapped to trees throughout the property. About the size of a box of tissues, they record the surrounding forest for 90 minutes at sunrise and at sunset, times when the murrelets are most likely to fly in with a mouthful of fish for their chicks. (Last year, the League used similar methods to track the northern spotted owl.)

The recording devices are battery-powered and store data on an SD card. James Martin/CNET

Later we bounce around the grove in an open ATV as Martin steers it down a steep rutted road. She stops at one point to show us one of the recording devices. Inside the waterproof casing is a control panel, a small LCD display and two SD card slots, all powered by four D batteries. Her business card is taped inside the door. After the SD card inside is full, the recordings are put through specialized software that can detect and filter out the bird's unique call from the background noise. If a murrelet is heard, Martin will note the location on a map of the property. Plotting nesting sites is critical to ensuring the murrelet's survival, which would be nearly impossible to do without the digital recordings.

"Once we know where they are, we can put down protections," she says. That might include closing off a portion of a trail during the spring and summer nesting season, or maybe not allowing the public into some areas because people can "bring their lunch, which turns into a food source for a predator."

Martin holds a map of the reserve showing the location of recording devices. James Martin/CNET

In planning public access to the reserve, the League also installed tree-mounted cameras to detect and track wildlife, and it's used drones to monitor the hard-to-reach areas of the property. It's also used light detection and ranging, or lidar, to map the forest's rugged topography. (Sort of like radar, lidar uses light waves to measure distances and generate three-dimensional information about the shape of an object or area.)

"It is forest primeval, so a lot of the most sensitive parts of the property are just plain hard to get to," Hodder says. "So the trails that we'll be putting in place will be ones that are respectful of that ecological sensitivity."

Elsewhere on the property, cameras watch for wildlife that may venture into meadows between the trees. Kent German/CNET

Redwood resilience

Though redwoods are now an inseparable image of California, 200 million years ago they stood throughout the entire Northern Hemisphere, across the North American continent and into Europe and Asia. Over time, though, climate changes like the last ice age diminished the trees to three areas, each of which is home to a distinct redwood species.

It's a lesson every California schoolkid learns early. Living near the ocean are the coast redwoods, like those in the Richardson reserve. Across the state on the western slope of the Sierra Nevada are the giant sequoia. Though shorter than the coast redwood (sequoias generally top out at 300 feet, or about the size of a 30-story building), they're much fatter and can live 1,000 years longer. The last species, the smaller deciduous dawn redwood, is native to China.

An outgrowth high above the ground on one redwood leads to a clone tree growing next to it. James Martin/CNET

Dressed in khaki pants and a shirt with sleeves rolled past his elbows, Hodder looks at home in the forest. He talks about the redwoods with a deep reverence, peppering his speech with superlatives like "spectacular" and "charismatic." Hodder says the league's founder, John C. Merriam, called redwoods the original face of nature. "It's one of the oldest ecosystems on the planet," he says. "Today when you think of the classic old-growth redwood forests, they're so characteristic of the American landscape and so iconic to the American identity."

In 2017, the League partnered with the University of California, Davis and Johns Hopkins University on a $2.6 million study to unlock the redwoods' genetic code to understand how the trees are responding to climate change (hint: they're growing faster). After five years, the Redwood Genome Project found the trees have six sets of chromosomes and 27 million base pairs of DNA -- the second-largest genome ever sequenced, after the Axoloti salamander in Mexico.

I talked to Hodder in an appropriate place, the Roberts Regional Recreation Area in the Oakland hills. At the time of California's 1850 statehood, this area was blanketed with a thick redwood grove. Some trees were so tall that ships sailing through the Golden Gate to the west used them as navigation points to avoid rocks in the bay. But as non-native settlers quickly discovered that the redwoods produced durable and beautiful lumber for homes and furniture, the trees disappeared. Today, visitors to the recreation area can enjoy a second-growth forest, or trees that were planted after those original trees were cut down.

Even a basal hollow as big as this won't kill a tree. James Martin/CNET

But some relics of that original forest remain. Hodder pointed to the stump of a tree that was 20 feet in diameter. The stump is a museum exhibit of what the forest used to be. "We believe the Oakland hills had some of the tallest redwood trees anywhere in the world. These were the real giants of the flora world," he says. "Within 20 years of the Gold Rush, every last one was gone."

Fortunately, redwoods have a strong weapon in the fight for survival: incredible resiliency. Their fibrous bark resists fire and decay, and they have no known parasites or diseases. Even the cavernous basal hollows aren't fatally damaging. "We can't find anything that kills a redwood," Hodder says. "Even when a redwood falls down, nothing eats it, so it can lie there for decades. A second-growth forest is a great example of how quickly the redwood forest can heal and begin to show its unique habitat characteristics and its incredible capacity to sequester carbon."

The redwood forest brings out the best in people. Sam Hodder

Still, redwoods today are vulnerable to both legal and illegal logging, among other threats. Eager to turn them into furniture and housewares, poachers can steal burls, the knobby growths at the base of a redwood that can grow into a clone tree. Marijuana cultivation may be the biggest concern. The isolation and cool weather of California's north coast has long made it attractive to both small- and large-scale pot growers. Years before recreational marijuana was legalized in California in 2016, growers cleared forests to plant illegal pot farms, poisoning the surrounding land in the process.

"The illegal siphoning of water out of the streams, the introduction of rodents to the food chain, the clearing of forest for growth areas and the spreading of fertilizer all have made a real impact on the ecosystem," Hodder says. "Legalization will likely have the positive impact of bringing those illegal growers out of the redwood forest, but it's too soon to tell."

A stream running through the Richardson reserve offers the League a place to study local amphibians. James Martin/CNET

A delicate balance

The challenges of saving the redwoods only seem to motivate Hodder. He started in conservation while in college, maintaining trails in the New England mountains during his summer vacations. After graduation, he worked for land stewardship agencies in California and Maine before joining the League a decade ago.

Today, he sees old-growth redwoods as a keystone of the conservation movement. While he recognizes that allowing the public into the Richardson Grove while keeping it relatively pristine will be difficult, it's also an exciting challenge. "We have a lot of faith and confidence in the visitors to redwood parks," he says. "These places inspire good behavior. The redwood forest brings out the best in people."

The long drive from the Bay Area and the few tourist services in the immediate area may discourage large crowds from making the trip. In comparison, Muir Woods National Monument, just across the Golden Gate Bridge from San Francisco, is so choked with visitors that reservations are required for entrance. For people who do make the pilgrimage to Richardson Grove, facilities will be minimal -- just a parking lot, trails and picnic tables, with no cafe, gift shop or museum.

Hodder says their reward will be just standing in the middle of a forest unlike anywhere else on the planet. "At the end of the day, the vast majority of the people who go to the redwood forest are there because they're inspired. And if they're not inspired yet, they will be by the time they take a walk."

Before we leave the Richardson Grove, we have lunch in a sunny meadow surrounded by a circle of skycraping trees. Unlike in the Oakland hills, where cars and airplanes are a constant background buzz, there are no signs of modern life around us. I can't help but be skeptical that visitors will treat this incredible place with the care it deserves, but as I touch the soft, flaky bark of the McApin tree one last time, I think about something Castaños said when we arrived. Experiencing the redwoods breeds respect for them, which is something a tree older than the Middle Ages desperately needs.