In early April 2007, less than three weeks after submitting my dissertation and receiving my doctorate at the University of California, Los Angeles, I got on a plane headed for Laos. It took four flights and more than twenty hours of flying time to get to the capital city of Vientiane. From there, I was bound for the Annamite Mountains: an eight-hour drive from Vientiane, then onward by truck, hand tractor (tok tok), and boat.

The remote Annamite Mountains run 680 miles (1,100 kilometers) along the border between Vietnam and Laos, reaching into northern Cambodia. This range divides the Mekong River Basin to the west from Vietnam’s narrow coastal plain to the east. The mountains are home to exceptional biodiversity. After the Vietnam War ended, Laos closed to Westerners, but in the early 1990s, the borders began to open. Biologists began to document fascinating endemic wildlife, some new to science, including the enigmatic saola (Pseudoryx nghetinhensis), a critically endangered bovine that, due to its rarity, has been dubbed the Asian unicorn. Perhaps the most miraculous discovery was that of the endangered Laos rock rat (Laonastes aenigmamus), a rodent identified as a surviving member of a family (Diatomyidae) previously thought to have gone extinct about eleven million years ago.1

Plant biodiversity in this mountain range is exceptionally rich as well, and many new species have been documented.2 When I initially arrived in the foothills, I could not have imagined that I would become part of one of these discoveries: the first biologist to collect samples of the majestic Asian swamp cypress (Glyptostrobus pensilis) growing in the country. This critically endangered species—locally known as mai hing sam—is currently documented in only two other heavily degraded populations, both in Vietnam. The mai hing sam in Laos are the only old-growth specimens in the world, and in recent years, the stands have been increasingly threatened by agricultural development and poaching for the luxury timber market. The protection of the few hundred remaining individuals in Laos has become my mission.

Arriving in Laos

Photograph of river flowing through tropical forest with mountains on horizon
The Annamite Mountains—known for complex topography, geography, and climate—harbor some of the most-contiguous moist forests in Indochina. Association Anoulak

My journey to the Annamite Mountains had begun four months earlier, when a member of my doctoral committee, Phil Rundel, emailed me with a proposal to work on a project in an especially remote part of Laos. I was immediately intrigued by the biodiversity, and the thought of getting away from my computer days after finishing my dissertation was alluring. Yet, I was hesitant. The opportunity involved working as a restoration ecologist on a World Bank hydropower project. As a wetland and riparian ecologist by training, I had always focused my research and professional work on protecting rivers and streams, not damming them.

Rundel encouraged me to research both points of view—pro- and anti-hydropower dam. On my breaks from dissertation writing that winter, I read articles and websites from advocates and opponents (including, among the latter, International Rivers and other nongovernmental organizations). I also corresponded with wildlife biologists who would be working on the project. The work was part of mitigation actions for the Nam Theun 2 Hydropower Project and supported the development of a national park in the reservoir’s headwaters. At more than 1,300 square miles (3,500 square kilometers), this protected area is one of the largest remaining contiguous areas of forests on the Indochinese Peninsula.3

Ultimately, I made a pragmatic decision: there was no stopping the dam, but I could work for the wildlife by helping to develop a conservation plan. I would work closely with James Maxwell, a renowned botanist from Chiang Mai University in Thailand, along with a team of wildlife biologists from a multitude of disciplines. Our mission was to assess wetland habitat on the Nakai Plateau—located high within the Annamite Mountains—before it was flooded by the reservoir. We would document the wetland vegetation and develop a wildlife management plan that included the restoration of habitat within an area known as the Nakai–Nam Theun National Protected Area. Little did I know I would be acting as field coordinator once I arrived, a task that I was comfortable with from fifteen years of managing restoration projects in the United States but not nearly as easy in this new landscape and culture.

The Discovery

The Annamite Mountains contain some of the last relatively intact moist forests in Indochina, unique due to the region’s complex geology and climate, and relatively inaccessible due to the steep topography. Initially, working with Maxwell proved extremely difficult. He could not understand why I had been hired on this project, since all my botanical experience was in the United States. He was standoffish and focused on collecting rare wildflowers he encountered. As we settled into the work, however, we bonded. He proved to be an exceptional mentor and friend, and in the years to come, I would stay with Maxwell and his wife in Thailand on multiple occasions.

Our standard workdays were reminiscent of my first fieldwork experiences in the hot, humid wetlands of coastal Georgia, where I had grown up. When we arrived in Laos, it was the height of the dry season and unbearably hot in the late afternoons. We started at sunrise to avoid the heat, first eating a bowl of pho, a noodle soup loaded with fragrant mint, crunchy cabbage, long beans, and assorted leathery forest leaves. In the field, we lugged our plant presses everywhere, as everything we collected went immediately into the press. The afternoons were sticky and oppressive in the open wetlands. We ended around four o’clock when we couldn’t take the heat anymore, giving us time to process our plant specimen and clean up our notes. At that point, the plants went directly from the presses into rice sacks with alcohol for preservation.

Map of preserved areas in Laos
The author located Glyptostrobus pensilis within the Nakai–Nam Theun National Park. The discovery was made while assessing wetland habitat and developing a wildlife management plan for the Nam Theun 2 Hydropower Project. Arnold Arboretum, ESRI, Garmin, and GIS Community

We surveyed all the herbaceous wetlands across the Nakai Plateau. These wetlands intermingled with rice paddies and were often used as grazing pasture. We began our collections in large, easy to access wetlands on the south side of the Nam Theun River. To guide us, we used paper topographic maps. We then made our way to more forested wetlands and riparian forests, northwest towards the dam site and onward to an area that was nicknamed Thousand Islands because of how the landscape flooded during the monsoon rains. From there we continued east, across the river, near the foothills of the Annamite Mountains.

The first potential wildlife habitat restoration site we visited was northeast of Thousand Islands, near the Nam Xot tributary to the Nam Theun River. Our colleague Pierre Dubeau, a geospatial scientist who had sited these potential restoration areas, exuberantly walked downstream through the forested wetland toward an area with large wetland grasses (Neyraudia reynaudiana). Maxwell and I followed Dubeau and wildlife biologist Rob Timmins, who was carrying an umbrella in the sprinkling warm afternoon rain. We agreed that this would be a great open location, ideal for wildlife habitat restoration. As we trudged back among a mucky mess of the forested wetland swamp, I stumbled over something and fell to my hands in the soggy soils. I slowly got up, shook off the fall, and investigated what I tripped over. It looked like a pneumatophore—the cypress knees I knew from my childhood in coastal Georgia, where bald cypress (Taxodium distichum) are a dominant feature of the swamps.

I looked up to find the tree it might be attached to, and sure enough, an enormous conifer towered above me. I looked up at this red-barked giant and saw something wonderfully strange and familiar. It looked like a cross between the bald cypresses that I knew from Georgia and the coastal redwoods (Sequoia sempervirens) from California, both members of the cypress family (Cupressaceae). I found several other knees as I walked up to inspect the tree. This, I proclaimed to Maxwell, must be a very special tree! Maxwell, however, like many other tropical botanists, was not as interested in conifers as much as the epiphytes that might grow on them. He thought nothing of it. Meanwhile, I collected the samples of small cones, foliage, and bark of this tree, which I sent to conifer expert Philip Thomas at the Royal Botanic Gardens, Edinburgh, for identification.

Documenting the Mai Hing Sam

Conifers are dominant or codominant parts of primary- and secondary-growth evergreen forests throughout the Annamite Mountains. In Vietnam, for instance, the mountains host a particularly rich assemblage of thirty-three conifer species, of which the cypress family (Cupressaceae) has seven.4 When I asked people in the neighboring Lao communities about the enormous tree that I had encountered, they provided a name: mai hing sam. Mai means “tree,” hing is a modifier for the kind of tree, and sam means “swamp,” or what ecologists would describe as a forested wetland.

As it turned out, the mai hing sam was, indeed, special. When Philip Thomas replied to my email, he identified the species as Glyptostrobus pensilis (known as the Asian swamp cypress), which the International Union for Conservation of Nature has classified as critically endangered.5 In 2007, the scientific community was aware of only 250 individuals of this species in the wild in Vietnam, where most were spindly, unhealthy young trees, growing in two small stands in the middle of coffee and corn plantations. Other stands in China were presumably planted.6 Due to its rot-resistant wood, Glyptostrobus pensilis is highly sought after in the luxury timber market and is used for a variety of structural and boat-building uses by local communities. It is threatened (like so many endangered species) by illegal logging.

As I learned more about the two populations in Vietnam, I realized how remarkable the mai hing sam in Laos really were. The trees in Vietnam grew very close together and, like those in China, appeared like they could have been planted. Boardwalks had been built within the stands to get around. Dams located beneath each of the stands were used for agricultural irrigation and raised the water levels for the trees significantly. In contrast, the trees that we observed in Laos were erect and widely spaced, as expected for a wild population. The crowns of the mai hing sam in Laos were only found in the top third of the trees, with no limbs below for us to climb to the seed-bearing cones. In the Vietnam population, perennial and annual branchlets were numerous along the main bole, appearing to be epicormic growth. This form suggests that the trees in Vietnam were responding to stress from inundation. Also, some of the trees in Vietnam were cut down years ago and had resprouted.7

Photograph of Glyptostrobus standing in center of rice paddy
Forests in the Annamite Mountains are rapidly disappearing due to forestry, agriculture, and hydropower development, along with other causes. Philip Thomas (right) stands beside Glyptostrobus pensilis within a rice paddy. David McGuire

I immediately told my colleagues about the mai hing sam discovery so that we could develop a strategy to describe and protect this stand. I also informed the Nam Theun 2 Power Company (NTPC) of the discovery and asked to spend time describing the tree and its ecology and to have a surveyor document their elevation relative to the proposed reservoir footprint. I was not allowed time to document this stand properly, however, and I was only able to record the number and size of the trees and basic soil characteristics. There were approximately one hundred trees in the stand, and many were three feet in diameter at breast height. We only had very rough elevation information from our GPS units, but it was clear that the trees—along with many others that we were unable to document—would likely be within the reservoir footprint.

In desperation to protect these rare trees, I contacted the Nam Theun 2 Panel of Experts, an audit group that was in charge of assessing the environmental and socioeconomic impacts of the dam, during their visit to the Nakai Plateau in August 2007. One of the members, the American conservation biologist Lee Talbot, joined me on a tour of this newly discovered mai hing sam stand. Nothing seemed to come of the visit, however, and unfortunately, I didn’t find anything about the trees in the panel’s next report.8 I proposed to my contacts at NTPC to collect as many seeds as possible and try to propagate and grow more trees. NTPC thought it was a great idea and gave us the go-ahead.

Developing a Restoration Protocol

At the time, mai hing sam had never been successfully propagated from wild-collected seed. As a result, several critical facts about restoration protocol were unknown to scientists: What time of the year do the seeds mature in the mountains of Laos? How long is their seed viable? Do they produce seeds every year? Did we need to treat the seeds before sowing them? Under what conditions would they propagate and survive? What we did know was that all conifer seeds are wind dispersed, so we hypothesized that their dispersal is probably connected to the windy part of the year, which occurs toward the end of the monsoon season.

Our first challenge was logistical: how would we collect seeds from cones high in the canopies, sometimes one hundred or more feet high. Maxwell—who, by this point, had returned to Thailand where he lived—often hired local tree climbers to make collections. But this method requires low branches or woody vines growing up the trunk, as the climbers do not use any specialized equipment. We put our heads together and came up with an unusual plan. We placed large tarps under the trees and hired boys with slingshots to shoot rocks up into the canopies of the trees so that the seeds would fall onto the tarps. We tried this method, and miraculously it worked. We got thousands of cones and hundreds of thousands of minute winged seeds.

The next challenge was to clean and propagate the seeds. This process was not managed by a conifer expert like Philip Thomas, as I had hoped. Rather, NTPC hired a commercial contractor to propagate the seeds in a local nursery. The contractor had no familiarity with this sensitive species, and only twelve seedlings germinated. Of those, only four grew to maturity. In restoration and horticultural propagation, this rate is not considered successful, but it was a start.

In 2008, NTPC planted the four trees at the confluence of two small streams behind the house occupied by the director of the Watershed Management and Protection Authority. This area was somewhat protected and easy to monitor, although soil characteristics were not similar to the natural conditions of the peat swamps in which the trees naturally grew. In 2015, when I first observed these trees, they were about six feet in height, and on my last expedition, in January 2020, they had reached over sixteen feet. The key to the survival of these four trees, I believe, was sustained high soil moisture during their establishment period and protection using sturdy exclusion fencing to fend off the cattle and water buffalo that munch on the succulent foliage.

Threats to Wetland Habitat and Endangered Species

After my contract was completed in 2009, I returned to California, where I became an assistant professor at the University of San Francisco. I vowed to go back to look for more mai hing sam in the Nakai–Nam Theun National Protected Area. Southeast Asia is experiencing rapid habitat loss, biodiversity declines, and risk of species extinction primarily due to unsustainable harvesting of forest resources and conversion for agriculture. Lack of enforcement and pressure to develop rice paddies has led to the decline of wetland habitat and continued poaching in the protected areas.9 Nearly every species of softshell turtle, terrapin, or tortoise is threatened with extinction. Populations of exceptionally rare species, such as the saola, are too low and fragmented to be viable.10 Considering these threats, I knew that we needed to mount a concerted effort to document and conserve mai hing sam in the region.

Phil Rundel, who had first encouraged me to participate in the project in Laos, recommended that I apply for National Geographic funding. I spent two years getting collaborators on board and finding out from contacts if there were any other trees in the national protected area. Maxwell and I corresponded regularly during this period. Likewise, Philip Thomas was a huge source of support and encouragement. Finally, in the spring of 2014, my collaborators and I received funding, and we went on to get permits and work on the expedition plan that summer.

With the help of National Geographic funding, we were able to document more than six hundred other mai hing sam between ten and thirty miles from the original stand. These plants occurred in the newly renamed Nakai–Nam Theun National Park, an area that has been under the management of the Watershed Management and Protection Authority since 2005. The trees in the oldest stand are more than three feet in diameter at chest level and five hundred to more than one thousand years old. Many of them are over six feet in diameter, and the largest is over ten feet. (We recorded 11.2 feet—3.4 meters—but it’s difficult to get the measuring tape behind all the woody vines and strangler figs on the trunk.) The neighboring communities call the largest tree the “mother tree.” It is more than 138 feet (42 meters) in height. We believe it could be two thousand years old, but it is not the tallest tree: that claim goes to one we documented at 184 feet (56 meters) tall.

While these trees are protected in the park, illegal activities still occur. Sometime between September 2015 and February 2016, two hundred mai hing sam were logged, leaving the total known population at approximately four hundred individual trees. This event was deeply upsetting, especially because, as I later learned, the individuals responsible were aware of the conservation importance. The Laos government took the event seriously and not only arrested the local Lao poachers but aggressively pursued the company in Vietnam that had hired them. Fortunately, the neighboring communities protected the mother tree from the poachers. Another factor that might have contributed to its protection is that the oldest trees are often hollow at the base, much like coast redwoods in California. The younger trees have solid trunks that are more desirable to poachers. This event shifted our project’s goals and objectives to focus on community-based restoration program and to identify and protect other unknown stands in the region.

Photograph of tree planting in Laos
The author (right) plants a Glyptostrobus seedling on National Tree Planting Day in May 2019. More than one hundred Laos government officials participated in the event, including Axay Vongkhamsao, head of the environmental division at NTPC (left); Khamthone Vongphachanh (center); and Thong Eth Phayvanh (second from right), the deputy general director of the Department of Forestry and director of the Watershed Management and Protection Authority. Gretchen C. Coffman

Each November, between 2017 and 2020, we collected seeds from the remaining stands. In the first two years, we propagated two thousand seedlings; however, many of these did not survive. We have learned a lot about propagation from these trials, and our team is actively developing improved propagation and planting techniques to restore stands of the mai hing sam in strategic areas of the watershed. We are excited to collaborate with colleagues in Vietnam and China to restore populations there as well. The urgency is clear: after the poaching occurred, the government intervened before the logs were removed from the forest. Some of the fallen trees were more than a thousand years old, and now those trunks remain as warnings on the forest floor. With these threats in mind, our work continues, sustained by the promise of the small seedlings.


  1 To learn more about recently documented mammal species in the Annamite Mountains: Dawson, M. R., Marivaux, L., Li, C., Beard, K. C., and Metais, G. 2006. Laonastes and the “lazarus effect” in recent mammals. Science, 311(5766): 1456–1458. doi:10.1126/science.1124187; MacKinnon, J. 2000. New mammals in the 21st century? Annals of the Missouri Botanical Garden, 87(1): 63–66. doi:10.2307/2666208

  2 Recent botanical discoveries in the Annamite Mountains include many new orchid species. Also, Brendan Buckley, from Columbia University, documented remarkable old-growth specimens of another cypress family species, Fokienia hodginsii, growing in Vietnam’s Bidoup Nui Ba National Park. The oldest specimens he found are more than twelve hundred years old, and the tree-ring data have supported Brendan’s research on long-term climate change in the region, including primary evidence for the fall of the Angkor civilization. Sano, M., Buckley, B. M. and Sweda, T. 2009. Tree-ring based hydroclimate reconstruction over northern Vietnam from Fokienia hodginsii: eighteenth century mega-drought and tropical Pacific influence. Climate Dynamics, 33: 331–340.

  3 Robichaud, W. G., Marsh, C. W., Southammakoth, S., and Khounthikoummane, S. 2001. Review of the National Protected Area System of Lao PDR. Vientiane, Lao PDR: Lao-Swedish Forestry Programme, Department of Forestry and IUCN; Scudder, T. 2020. A retrospective analysis of Laos’s Nam Theun 2 Dam. International Journal of Water Resources Development, 36(2–3): 351–370. doi:10.1080/07900627.2019.1677456

  4 Of the thirty-three conifer species documented in the Annamite Mountains in Vietnam, thirteen are members of the pine family (Pinaceae). The cypress and yellowwood families (Cupressaceae and Podocarpaceae, respectively) include seven species each. The yew family (Taxaceae) has five species, and the plum yews (Cephalotaxaceae) have one. In particular, the Da Lat Plateau in central Vietnam has sixteen species of conifers, representing the highest conifer diversity in Indochina. Ninety percent of these, however, are nationally threatened. Loc, P. K., The, P. V., Long, P. K., Regalado, J., Averyanov, L. V., and Maslin, B. 2017. Native conifers of Vietnam—A review. Pakistan Journal of Botany, 49(5): 2037–2068.

  5 While Glyptostrobus has few extant populations, the genus has existed for more than one hundred million years, dating back to at least the middle Cretaceous, and was once quite abundant. Fossils of the genus can be found across all of Asia and North America and as far north as Axel Heiberg Island in the Arctic. See: Greenwood, D. R., and Basinger, J. F. 1994. The paleoecology of high-latitude Eocene swamp forests from Axel Heiberg Island, Canadian High Arctic. Review of Palaeobotany and Palynology, 81(1): 83–97. doi:10.1016/0034-6667(94)90128-7; Vickulin, S. V., Ma, Q. W., Zhilin, S. G., and Li, C. S. 2003. On cuticular compressions of Glyptostrobus europaeus (Taxodiaceae) from Kaydagul Formation (Lower Miocene) of the Central Kazakhstan. Acta Botanica Sinica, 45(6): 673–680; Jahren, A. H. 2007. The Arctic forest of the middle Eocene. Annual Review Earth Planetary Science, 35: 509–540.

  6 To read more about the stands in Vietnam and China, see: Averyanov, L., Phan, K., Nguyen, T., Nguyen, S., Nguyen, T., and Pham, T. 2009. Preliminary observation of native Glyptostrobus pensilis (Taxodiaceae) stands in Vietnam. Taiwania, 54(3): 191–212. doi:10.6165/tai.2009.54(3).191; Tang, C. Q., Yang, Y., Momohara, A., Wang, H.-C., Luu, H. T., Li, S., Song, K., Qian, S., LePage, B., Dong, Y.-F., Han, P.-B., Ohsawa, M., Le, B. T., Tran, H. D., Dang, M. T., Peng, M.-C., and Wang, C.-Y. 2019. Forest characteristics and population structure of Glyptostrobus pensilis, a globally endangered relict species of southeastern China. Plant Diversity, 41(4): 237–249.; Wu, X., Ruhsam, M., Wen, Y., Thomas, P. I., Worth, J. R., Lin, X., Wang, M., Li, X., Chen, L., Lamxay, V. Le Canh, N., and Coffman, G. C. 2020. The last primary forests of the Tertiary relict Glyptostrobus pensilis contain the highest genetic diversity. Forestry: An International Journal of Forest Research, 93(3): 359–375. doi:10.1093/forestry/cpz063; Li, F. G., and Xia, N. H. 2004. The geographical distribution and cause of threat to Glyptostrobus pensilis (Taxodiaceae). Journal of Tropical and Subtropical Botany, 12(1): 13–20.

  7 It is interesting to note that pneumatophores of the trees in Vietnam measure about 2 feet (0.6 meters) tall on average, similar to those in Laos; however, the pneumatophores were more abundant in Laos, sometimes numbering dozens per tree and usually much shorter.

  8 McDowell, D., Scudder, T., and Talbot, L. M. 2007. Twelfth Report of the International Environmental and Social Panel of Experts for the Nam Theun 2 Hydro Project. Vientiane: Lao People’s Democratic Republic.

  9 For more on the environmental threats in Southeast Asia: Hughes, A. C. 2017. Mapping priorities for conservation in Southeast Asia. Biological Conservation, 209: 395–405. doi:10.1016/j.biocon.2017.03.007; Sodhi, N., Posa, M., Lee, T., Bickford, D., Koh, L., and Brook, B. 2010. The state and conservation of Southeast Asian biodiversity. Biodiversity and Conservation, 19(2): 317–328. doi:10.1007/s10531-009-9607-5; Nooren, H., and Claridge, G. 2001. Wildlife trade in Laos: The end of the game. Gland, Switzerland: IUCN-The World Conservation Union; Appanah, S., Shono, K., and Durst, P. B. 2015. Restoration of forests and degraded lands in Southeast Asia. Unasylva, 66(245): 52–62.

10 For more on conservation of the saola: Tilker, A., Long, B., Gray, T. N. E., Robichaud, W., Van Ngoc, T., Vu Linh, N., Holland, J., Shurter, S., Comizzoli, P., Thomas, P., Ratajszczak, R. and Burton, J. 2017. Saving the saola from extinction. Science (American Association for the Advancement of Science), 357(6357): 1248. doi:10.1126/science.aap9591

The map in this article was created using Esri, USGS, USFS, NGA, NASA, CGIAR, N Robinson, NCEAS, NLS, OS, NMA, Geodatastyrelsen, Rijkswaterstaat, GSA, Geoland, FEMA, lntermap and the GIS user community.


I dedicate this manuscript to the late James Maxwell (1945–2015). He was an intrepid botanist, fervent collector, a character like no other, exemplar taxonomy mentor, and trusted friend.

Photograph of James Maxwell collecting in open wetland.

Gretchen C. Coffman is a wetland restoration ecologist and a senior lecturer at the National University of Singapore. She teaches wetland restoration ecology, biogeography, applied ecology, and research methods in physical geography. From 2010 to 2019, she taught field ecology courses in the Environmental Science Department, the Masters of Science in Environmental Management program, and the Environmental Studies program at the University of San Francisco.

Citation: Coffman, G. C. 2021. Discovering the Majestic Mai Hing Sam of Laos. Arnoldia, 78(3): 18–27.

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