Changing Planet

What’s the Worth of a Single Tree Species?

Giant cypress knee
This is not the stump of an old tree, but simply one of the many knees on a well aged Chinese swamp cypress. (Photo courtesy Gretchen C. Coffman)

High in the Annamite Mountains of central Laos, among hill-tribe villages, grows the majestic—and critically endangered—Chinese swamp cypress (Glyptostrobus pensilis). I’m here to find these trees, study them, and work for their protection.

Why is this particular tree worth protecting? I get this question a lot: from villagers in the area where the last wild ancient trees are still standing, from government officials, from colleagues and students, from friends and family at Thanksgiving.

Because I teach about entire ecosystems at the University of San Francisco, it’s usually pretty easy for me to explain why an interconnected world of plants and animals functioning together is significant. But is a single species of tree really so important? I pause to reflect on this myself.

The Knee You Need to Know

What we call a “cypress knee,” and scientists call a “pneumatophore,” (the thing I tripped over a few years ago in Laos) is a root-like organ that trees such as the Chinese swamp cypress thrust up above the earth and then back down again in order to stabilize the tree’s huge biomass in wet, spongy soil. That first tree I saw was enormous, which means that it had been growing and shaping its local environment for at least two centuries, above and below ground.

Chinese swamp cypress can reach 147 feet (45 meters) tall here in Laos. (Photo courtesy Gretchen C. Coffman)

In the photo at the start of this post, you can see how large these cypress knees can grow in the ancient forests we visited, and in the video below you can see the kind of swamp soil from which these giant trees can grow at an elevation up to 2550 feet (850 meters).

In the video, you’ll see that our photographer, David McGuire, had to secure his sandal straps with extra bits of string because the soil is so wet and fine-grained that it renders Velcro useless. An average adult can hardly stand up straight here and would often sink to his or her knees. But the cypress towers over the landscape at more than 147 feet (45 meters) tall!

largest glypto
Huge woody vines, called lianas, like this strangler fig, climb up giant cypresses and give our team easy routes to the top to collect samples of the cypress’s twigs. (Photo courtesy Gretchen C. Coffman)


Huge Home for Many

Swamps in Laos are dense with many layers of vegetation, and hence are rich with wildlife. Our team botanist, Philip Thomas of Royal Botanical Gardens Edinburgh (RBGE), and wildlife biologist, Rob Timmins, found a large number of orchids and other epiphytes (plants that live on other plants but get their food and water from the air), ginger, rattan, pandana, and signs of frogs, birds, and fish in the adjacent rivers, as well as elephants (“Laos” is said to mean “land of a million elephants”), Asian black bears, sun bears, wild boar, and muntjacs (a kind of small, fanged deer).

We are always on the lookout for the shy, unicorn-like deer that the Lao people call the “saola.”

Bear Claws on Glypto
Claws on the trunk of a Chinese swamp cypress attest the presence of an Asian black bear. (Photo courtesy Gretchen C. Coffman)

A Generous Resource for the Locals

The local name in Laos for the Chinese swamp cypress is “Mai Heng Sam.” The closest English translation would be, “large water pine.” The wood is highly resistant (like that of redwoods) to fire, microbial rot, and termite infestation. As small villages grow throughout rural montane Laos, locals clear terrain for the creation of rice paddies and use the cypress wood for many projects.

I have visited many villages where the local people have been harvesting the tree for building materials, most importantly shingles for roofing and siding, structural posts, doors, and planks for stairs. Historically they even used them for local wooden boats.

Glypto house with person
The microbe-, fire-, and water-resistant properties of Chinese swamp cypress wood make it ideal for home construction. (Photo courtesy Gretchen C. Coffman)
rice paddy glypto
A few Chinese swamp cypress trees remain amid a rice paddy worked by people who use the small cabin in the center for shelter. (Photo courtesy Gretchen C. Coffman)

A Win-Win for Plants and People

The flourishing of small rural villages need not threaten the local cypress populations.

In fact, as we have been discussing this restoration project with village head-men in Laos, we have learned that they are very much invested in the conservation of this old-growth arboreal species. We have been relying on our collaborators in local villages to help us find and document cypress stands, and in return, we will assist them in protecting sources of clean water, and in creating the infrastructure to generate micro-hydroelectric power for villages.

The head-man, Sim Than, of Ban Theung is seen below taking us to visit a small waterfall whose energy he would like to harness in order to bring electricity to his village. It’s a great plan that should be fairly easy to implement. (Note that he’s sitting on a big cypress knee!)

Sim Than, a local head-man, sits atop a prominent cypress knee. (Photo courtesy Gretchen C. Coffman)
Sim Than, a local head-man, sits atop a prominent cypress knee. (Photo courtesy Gretchen C. Coffman)

Our hope is that this conservation project will not only protect and support biodiversity, but also improve the quality of life in the mountain villages of Laos.

Picture of a young girl carried in a sling
It starts with protecting trees, but it pays off with helping the local humans, too. (Photo courtesy Gretchen C. Coffman)

When we consider the unique structure and characteristics of these trees, the habitat they provide for many other species, and the resource they provide for the people of the area, it’s clear that one species really can be of major importance.

But then again, it’s all because of how it fits into and helps the world around it.

Our team is the same way. In the next post, we’ll introduce you to more of the different team members that make all this work possible and fruitful.


Read All Chinese Swamp Cypress Posts

Dr. Coffman is an Assistant Professor in the Environmental Science Department at University of San Francisco. Dr. Coffman's current research focuses on scientific questions with high relevance to management problems, mainly related to riparian plant ecology, restoration, and invasive plant biology in river and wetland systems of mediterranean-type and tropical climates. She has on-going research projects along rivers in coastal southern California, the San Francisco Bay Area, the Central Valley of California, and Central Laos and coastal Cambodia. She teaches courses at USF in applied ecology, environmental science, restoration ecology, wetland delineation, field botany, and ecosystem ecology in both the undergraduate Environmental Science Department and Environmental Management masters program. She received funding from National Geographic Conservation Trust to document the critically endangered swamp cypress of Laos in 2014-2015.
  • Susanne Friedrich

    Thanks for this fantastic insight into the interaction of this amazing tree with its surrounding wildlife and its importance for the humans that live in its vicinity. Looking forward to the next post!

  • Todd Haiman

    Wonderful article thank you for posting. Explaining how the tree is critical to the local environment is so important.
    Consider all that trees do for us as humans, they are a species that sustains, rather “cradles” our survival … they provide oxygen, control soil erosion, offer shade, filter air pollution, recycle water, sequester carbon and significantly more. More to read on my blog

About the Blog

Researchers, conservationists, and others share stories, insights and ideas about Our Changing Planet, Wildlife & Wild Spaces, and The Human Journey. More than 50,000 comments have been added to 10,000 posts. Explore the list alongside to dive deeper into some of the most popular categories of the National Geographic Society’s conversation platform Voices.

Opinions are those of the blogger and/or the blogger’s organization, and not necessarily those of the National Geographic Society. Posters of blogs and comments are required to observe National Geographic’s community rules and other terms of service.

Voices director: David Braun (

Social Media