China Has a Forest of Trees Scientists Declared Extinct — And Nobody Can Explain It

[00:00:00]The entire botanical establishment had agreed it was gone.

[00:00:04]The fossil record was settled. The extinction was recorded on every continent. Metasequoia was as dead as the dinosaurs it had outlived. Until a government forester followed a tip into a mountain valley in central China [music] and found something that was not supposed to exist.

[00:00:22]In the autumn of 1943, a Chinese government forester named Wang Zhan arrived in a remote valley in Lichuan County, Hubei Province, following a tip from a colleague who had passed through 2 years earlier.

[00:00:36]The trip required days of travel through mountain terrain with no roads. [music] What Wang found at the end of that journey was a grove of enormous deciduous trees [music] growing beside a small shrine in a village called Modao.

[00:00:51]Some of the trees were 60 ft tall. Their trunks were massive, tapered and buttressed at the base.

[00:00:58]The local people called them shui-sha, water fir.

[00:01:02]They had been growing near that shrine as far as anyone in the village could say, for longer than living memory extended.

[00:01:09]Wang took samples. He packed them and carried them out of the mountains and sent them to researchers in Chongqing, the wartime capital of China.

[00:01:18]The Second World War made further study impossible.

[00:01:22]The samples [music] sat.

[00:01:24]2 years before Wang entered that valley, on the other side of the world, a Japanese paleobotanist named Shigeru Miki had published a description of an extinct tree.

[00:01:35]The specimens Miki worked from were fossil plant material recovered from sediments [music] in Japan.

[00:01:42]The genus he named was Metasequoia.

[00:01:45]Based on everything the fossil record indicated, [music] Miki concluded the tree had been extinct for at least 5 million years.

[00:01:54]When botanists finally compared Wang Zhan's field samples [music] to Mickey's published description in 1946, they found something with no precedent [music] in 20th century science.

[00:02:05]The tree Wang had photographed and pressed [music] in that Hubei Valley was not merely related to Metasequoia.

[00:02:12]It was Metasequoia.

[00:02:14]Identical in every significant detail, >> [music] >> cone structure, leaf arrangement, branching habit, bark texture, >> [music] >> to the fossils Mickey had described as extinct.

[00:02:26]The entire botanical establishment [music] had agreed with Mickey.

[00:02:30]No living specimen had ever been reported. No field survey across Asia had flagged one. [music] The fossil record showed a genus that had dominated the entire northern hemisphere >> [music] >> for 17 million years, and then, somewhere around 5 million years ago, simply stopped appearing in the sediment.

[00:02:49]Except in [music] this valley.

[00:02:51]In one county.

[00:02:53]In one province. In a country the size of a continent.

[00:02:57]Where local people had apparently been digging young trees out of the ground and replanting them near their homes and rice fields and roads for as long as anyone [music] had been keeping any record of the place at all.

[00:03:11]When the discovery was formally announced in 1948, [music] scientists called it the greatest botanical find of the 20th century.

[00:03:19]>> [music] >> What they still cannot fully explain is the question at the center of the entire story.

[00:03:26]How a genus that [music] once stretched from the Arctic to the equatorial zones, that grew in forests above the North Pole during the warmest [music] periods in Earth's recent history, collapsed into a single isolated valley, a few thousand feet up in the mountains of central China, with no confirmed surviving population anywhere else on the planet for thousands of miles in any direction.

[00:03:53]This is that story.

[00:03:55]This is the full story from the Cretaceous forests where Metasequoia dominated entire continents to the wartime discovery that no field botanist had [music] predicted to the Harvard-funded seed expedition conducted with armed guards under a government export ban [music] to what peer-reviewed population surveys of the remaining wild trees now show about a species that survived 5 million years of isolation only to face >> [music] >> in the 21st century a reproductive crisis that its global distribution has not yet solved.

[00:04:32]Every claim in this video [music] is sourced from population studies published in Biological Conservation and Frontiers of Forestry in China. The detailed chronology of the discovery [music] compiled by researcher Shao Lixin Ma and the current IUCN Red [music] List assessment for Metasequoia glyptostroboides.

[00:04:53]This is not the version where [music] the tree was rediscovered and everything became fine.

[00:04:59]Most videos about the dawn redwood lead with the headline extinct [music] tree found alive and treat the discovery itself as the ending.

[00:05:08]This one follows the data into the field [music] surveys into the question of what the wild population at is actually doing right now and into the part of the story that the ornamental [music] tree catalogs never mention.

[00:05:22]Stories like this almost never make the news. [music] If you want to keep finding them, subscribe.

[00:05:28]New one every week.

[00:05:31]But before you can understand why that valley matters beyond its history, you need to understand what Metasequoia actually was and the scale of what it lost before a government forester noticed a large tree that the people of one Hubei village had always lived beside.

[00:05:48]The fossil record for Metasequoia extends back roughly 90 million years to the late Cretaceous period, the era of large sauropods and the last flowering of the non-avian dinosaurs.

[00:06:02]The genus was not a minor or peripheral element in that landscape.

[00:06:06]It was, by the evidence of the fossil record, a dominant tree across the entire northern hemisphere during the warmest intervals of the Paleogene and Neogene epochs.

[00:06:17]Metasequoia fossils have been excavated from Axel Heiberg Island in the Canadian High Arctic, standing stumps preserved in permafrost at latitudes where no tree survives [music] today.

[00:06:30]They have been recovered from Svalbard, from Greenland, from deposits across Europe and Japan, from Eocene sediments in North Dakota and the interior of the American West.

[00:06:43]During the Eocene epoch, >> [music] >> roughly 50 to 35 million years ago, Metasequoia forests grew above the Arctic Circle.

[00:06:52]The poles were warm enough then that no permanent ice sheets existed, and mean annual temperatures at high latitudes were comparable to modern temperate forests.

[00:07:03]Metasequoia was the tree those polar forests were largely [music] built from.

[00:07:08]On Axel Heiberg Island, in what is now the Canadian High Arctic, paleobotanists have recovered not just leaf impressions, but standing fossil stumps, trunks preserved upright in permafrost, still rooted in place >> [music] >> at latitudes where the sun does not rise for months in winter.

[00:07:28]These are not [music] distant relatives.

[00:07:30]They are the same species, or something so [music] close to it that the distinction may be nominal, growing in a place where today the average annual temperature sits well below freezing, >> [music] >> and nothing taller than low shrubs survives.

[00:07:46]Then, as global temperatures fell through the Oligocene and Miocene, the polar forests retreated.

[00:07:54]The Arctic [music] Metasequoia populations disappeared from the record.

[00:07:59]The European populations went silent.

[00:08:02]The North American populations followed.

[00:08:05]By the late Miocene, approximately 5 to 7 million years ago, >> [music] >> Metasequoia disappears entirely from the global fossil record, or almost entirely.

[00:08:16]One population in one narrow valley system in what is now [music] central China did not disappear.

[00:08:23]How it survived when everything elsewhere did not, when a genus that had populated the entire northern hemisphere went globally silent, [music] is the part of the story for which no complete explanation exists.

[00:08:37]Paleobotanists point to the terrain of the Hubei-Hunan-Chongqing border region as a likely refugium.

[00:08:44]Sheltered valleys, a relatively [music] stable microclimate, and the buffering effect of mountain topography may have protected the tree when conditions elsewhere became untenable.

[00:08:55]The hypothesis is reasonable. The problem is that the same kind of sheltered mountain terrain exists throughout much of central and southern China.

[00:09:05]Metasequoia survived in only one of those valleys.

[00:09:09]Why that one and nothing else for thousands of miles remains an open question.

[00:09:16]The discovery itself unfolded across seven years and a world war.

[00:09:21]In the winter of 1941, the same year Shigeru Miki published his fossil description of the extinct genus, a Chinese botanist named T. Kan was traveling through Hubei province when he noticed a large deciduous [music] tree growing on a roadside near Moudao Village.

[00:09:38]The tree had dropped its leaves by the time Khan arrived, and a bare-branched conifer in December yields nothing useful for botanical identification.

[00:09:48]He noted the tree.

[00:09:50]He continued on.

[00:09:51]No samples were taken.

[00:09:54]Wang Zhan's 1943 expedition [music] collected the first usable material.

[00:10:00]Professor Wan Chun Cheng of the National Central University in Nanjing sent expedition in 1946 after the war ended [music] for a complete survey.

[00:10:12]It was on this expedition that the collected specimens were first systematically compared to Miki's published fossil description.

[00:10:20]The match was unambiguous.

[00:10:23]The tree had been growing beside a village shrine in Lichuan County. Local farmers had been digging it up and transplanting it near their homes for reasons that would only become scientifically legible much later.

[00:10:35]In all morphological particulars, it was Miki's extinct genus alive and reproducing.

[00:10:42]Professor Xian Xuhu, director of the Fan Memorial Institute of Biology in Beijing, and the first Chinese national [music] to receive a doctorate in botany from Harvard University, co-described the species with Cheng.

[00:10:56]Their paper, published in May 1948, named it Metasequoia glyptostroboides and formally introduced to the scientific a living species of a genus previously known only from fossils.

[00:11:10]The international response was immediate and unusually practical.

[00:11:16]Dr. Elmer Merrill, director of the Arnold Arboretum at Harvard, began organizing a seed-collecting expedition before Hu and Cheng's [music] paper was even in press.

[00:11:27]The 1947 Harvard expedition to Lichuan County did not proceed with standard botanical courtesy.

[00:11:34]China was already sliding toward full civil war between the Nationalist government and Communist forces, and the situation in Hubei was unstable.

[00:11:44]The Chinese government maintained a prohibition on the export of living plant genetic material, and the expedition required armed guards to complete its work.

[00:11:54]4 lb of seed were collected from the Modaoli Valley trees and transported to Boston.

[00:12:00]Seeds arrived at Arnold Arboretum in early 1948.

[00:12:05]Within the year, Merrill had distributed them to 76 institutions and individuals >> [music] >> across six continents.

[00:12:14]More than 600 individual seed packets [music] reached botanical gardens, universities, and arboreta worldwide. [music] In 1952, the Hoyt Arboretum in Portland, Oregon, recorded the first Metasequoia cone produced [music] in the Western Hemisphere in an estimated 6 to 8 million years.

[00:12:35]>> [music] >> A tree grown from those Harvard seeds had not only survived transplantation to a new continent, it had reproduced, >> [music] >> setting fruit as reliably as the fossils in the Arctic sediment had promised it once did.

[00:12:49]The tree became a popular ornamental across the United States, Europe, [music] Australia, and East Asia.

[00:12:56]It grows quickly, reaches impressive height, and turns deep amber in autumn before dropping its needles.

[00:13:04]It is one of the very few deciduous [music] conifers, a trait that surprises people who assume needles and conifer are inseparable terms.

[00:13:13]>> [music] >> There are now Metasequoia planted in parks from London to Los Angeles, in botanical gardens from Sydney to Seoul, on university [music] campuses, and in residential gardens on every inhabited continent.

[00:13:27]By any count, there are more living Metasequoia on Earth today than at any point [music] in the last several million years.

[00:13:35]This is where the story usually ends.

[00:13:38]It does not [music] end there.

[00:13:41]By 1983, field surveys counted 5,746 [music] individual Metasequoia trees in the Lichuan area, the original discovery site in Hubei.

[00:13:53]By 2003, >> [music] >> the same survey methodology returned a count of 5,388.

[00:14:00]The population had declined, but the more significant finding [music] was not the raw number.

[00:14:07]It was the age structure.

[00:14:09]A 2010 study published in Biological Conservation, in which researchers surveyed all known wild individuals of the species and compared their findings to surveys from the 1950s, found that the remaining trees ranged in age from roughly 41 to approximately 265 years, averaging near 95 years.

[00:14:32]There were, in practical terms, no young trees.

[00:14:36]Natural regeneration, the production of new seedlings that [music] successfully establish and grow, had effectively stopped.

[00:14:44]Multiple factors converged to explain the collapse of recruitment.

[00:14:48]Human disturbance in and around the habitat has increased [music] continuously since the 1940s, including selective cutting of surrounding forest cover, harvesting of fallen wood for fuel, cultivation of other crops [music] in the understory, and the compaction of soil around root systems from foot traffic at what has become a heritage and tourism site.

[00:15:12]Beyond the human pressure, the biology of the tree [music] itself creates obstacles.

[00:15:19]Seed germination rates in Metasequoia [music] Glyptostrobus under natural conditions run at approximately 33%.

[00:15:27]Seeds lose viability rapidly when exposed to [music] fluctuating moisture.

[00:15:32]And the specific habitat requirements for successful seedling establishment, open disturbed ground near reliable water sources free from competition and shading, are increasingly rare in a landscape that has been continuously inhabited and farmed for centuries.

[00:15:51]The IUCN Red List [music] classifies Metasequoia glyptostroboides as critically endangered.

[00:15:59]That classification [music] applies to the wild population, not to the global cultivated population.

[00:16:06]The distinction matters more than it might initially appear.

[00:16:10]A 2003 molecular study found that mean genetic diversity in natural Metasequoia populations ran between 10.5% and 33.3% of polymorphic loci.

[00:16:26]In cultivated populations worldwide, the same measure ran between 8.7% and 10.5% measurably lower.

[00:16:36]In the 1980s, research in Europe and North America found that second generation cultivated Metasequoia, trees [music] grown from seed produced by the first trees distributed worldwide from the 1948 Harvard collection, were showing signs of inbreeding depression, reduced disease resistance, and [music] diminished reproductive success.

[00:16:58]The researchers who documented this pattern wrote in 2012 that it was too early to call the conservation effort for the species a success.

[00:17:08]But perhaps the most disquieting element of the Metasequoia story is the one that appears in nearly every detailed historical account and receives almost no attention in the popular retelling.

[00:17:20]Wang Jian's photographs from 1943 did not show trees growing in undisturbed forest.

[00:17:27]>> [music] >> They showed trees growing beside a village shrine.

[00:17:31]Subsequent surveys found the wild population distributed across 45 villages in the Lichuan area, >> [music] >> with individual trees growing primarily along stream banks, roadsides, and field margins, the most heavily human-disturbed habitats in the landscape. [music] A significant proportion of the trees showed evidence of having been transplanted rather than naturally established.

[00:17:55]Historical accounts note consistently [music] that local inhabitants had a well-established practice of digging young trees from the surrounding terrain and planting them near their homes, beside their [music] water sources, and at property boundaries.

[00:18:10]Whether the Modaole Valley population is wild in any strict ecological sense, whether it reproduced and established [music] through natural processes without sustained human intervention, or whether it has been maintained, [music] at least partly, by centuries or possibly millennia of local planting, is a question that field ecology has not [music] definitively answered.

[00:18:35]No analysis has cleanly separated anthropogenically [music] transplanted trees from naturally established ones within the existing population. [music] The possibility exists that the species survival into the modern era was not primarily a function of some exceptional property of the Lichuan [music] terrain.

[00:18:55]It may have survived because local people who called it shwei-sha, water fir, happened to find [music] it useful or beautiful enough to keep moving seedlings from the ground around them into the places [music] where they lived.

[00:19:08]The type specimen, the individual tree from which Wang Jian collected [music] the samples that would eventually be identified, named, described, and distributed to 76 institutions on [music] six continents stands today in the Chinese Metasequoia Botanical Garden in Modu, Lichuan City, Hubei.

[00:19:29]Its trunk diameter is approximately 248 cm.

[00:19:33]It is old enough that no one is certain when it established or whether it did so naturally.

[00:19:39]It lives inside a tourist [music] park.

[00:19:42]Metasequoia glyptostroboides survived 90 million years.

[00:19:47]It survived the mass extinction at the end of the Cretaceous. It survived the ice advances that drove [music] it from the Arctic and from Europe and from North America. It survived 5 million years during which the entire scientific establishment, >> [music] >> working from the best available fossil evidence, was certain it was gone.

[00:20:08]The mechanism by which it made it through all of that is still not fully understood.

[00:20:13]What the field surveys from 2003 and 2010 show is that the population in that Lichuan Valley is now aging without replacement.

[00:20:24]The oldest trees are over two centuries old. The youngest are difficult to locate.

[00:20:30]The seeds barely germinate under natural conditions.

[00:20:33]The habitat that allowed any regeneration to occur at all has been steadily reduced for decades.

[00:20:41]90 million years of survival.

[00:20:44]And the part that nobody can fully explain >> [music] >> is not how the tree made it through the end of the dinosaurs. It is how the thread held at all and whether without a farmer in a mountain village who liked [music] the look of a particular tree and moved a seedling closer to his door, there would have been anything left to find in [music] 1943.

[00:21:07]The trees are still there, standing in stream valleys and beside roads in Lichuan County.

[00:21:13]60-ft trunks buttressed at the base, some of them more than two centuries old.

[00:21:19]The dawn redwood has outlasted almost everything that [music] has ever competed with it.

[00:21:24]What happens next is still being written.

[00:21:28]The trees that survived 90 million years of planetary change are now dependent on decisions being made by agencies that spent decades viewing them as a symbol of national pride rather than a species in active ecological crisis.

[00:21:44]The data on recruitment and regeneration suggests [music] the window for intervention is narrowing.

[00:21:49]If this is the kind of story that does not make the evening news, but probably should, there is another one on screen now.