Pando (tree)

Pando (from Latin pando 'I spread') is the name of a quaking aspen (Populus tremuloides) clone located in Sevier County, Utah, United States, in the Fishlake National Forest. A male clonal organism, Pando has an estimated 47,000 stems (ramets) that appear to be individual trees but are genetically identical parts of a single tree connected by a root system that spans 42.8 ha (106 acres). As a multi-stem tree, Pando is the world's largest tree by measures of weight, landmass and species, and is generally held to be the world's single largest organism by weight. Systems of classification used to define large trees vary considerably, leading to some confusion about Pando's status. Within the United States, the Official Register of Champion Trees defines the largest trees in a species-specific way; in this case, Pando is the largest aspen tree (Populus tremuloides). In forestry, the largest trees are measured by the greatest volume of a single stem, regardless of species. In that case, the General Sherman Tree is the largest unitary (single-stem) tree. While many emphasize that Pando is the largest clonal organism, other large trees, including Redwoods can also reproduce via cloning. Pando being the heaviest tree and the largest tree by landmass, while also being the largest aspen clone, leaves it in a class of its own. Friends of Pando and the Fishlake National Forest partner to study and protect Pando, working alongside the Utah Division of Wildlife Resources. Notable organizations that also study and advocate to protect Pando's care include the Western Aspen Alliance and Grand Canyon Trust. Discovery, naming and verification The Pando tree was identified in 1976 by Jerry Kemperman and Burton V. Barnes. A posthumous biography by Barnes's colleague, Daniel Kashian, details Pando's discovery: As a part of his aspen work in the West, Burt began to examine an extremely large trembling aspen clone southwest of Fish Lake, Utah, in the late 1960s and early 1970s. Using aerial photography and the same morphological differentiation techniques he developed for aspen at UMBS for his dissertation, Burt concluded that the aspen forest that covered about 106 acres was a single aspen clone, quite possibly the "world's largest organism." Other than a single publication about aspen clone size and another great story to tell his students, Burt's studies on the Fish Lake clone were relatively obscure. Work by Fishlake National Forest to understand and protect the tree began in 1987, according to interviews and articles written by Fishlake Forest as well as accounts gathered by Friends of Pando. Based on Barnes and Kempermans's 1976 paper noting Pando's discovery, Michael Grant, Jeffrey Mitton, and Yan Linhart of the University of Colorado at Boulder re-examined the clone in 1992 and described Pando as a single male aspen clone based on its morphological characteristics such as pollen production, leaves, and root structure. Michael Grant named the tree "Pando" which is Latin for "I spread" in an editorial which was later published in Discover Magazine. A large-scale genetic sampling and analysis was published in 2008 by Jennifer DeWoody, Karen Mock, Valerie Hipkins, and Carol Rowe. The research team's genetic study confirmed morphological analysis by Barnes and Kemperman as well as Mitton, Grant and Linhart, thus verifying Pando's size and scale of operation. Research and protection In late 1987, Fishlake National Forest began work to remove diseased trees and promote new growth using coppicing (a form of mechanical stimulation), which works by removing diseased stems, that in turn, stimulates a regenerative hormone response which spurs new growth. In 1993, Fishlake National Forest began work on the "Aspen Regeneration Project", installing fences to help control deer and elk who threatened to destroy the productive results of work to spur and protect new growth. Today, approximately 84 acres of Pando is protected by 8-foot wildlife controls, which work to control populations of mule deer (Odocoileus hemionus) and elk (Cervus canadensis), and to control human uses, such as off-road recreation and formerly permitted grazing by domestic cattle (Bos taurus). Additional fencing protections were added in 2025 bringing approximately 80% of Pando's landmass into protective care while also creating two simplified wildlife management bulwarks to move animals around the tree's landmass. Since the early 2000s, little information has been adequately corroborated about Pando's origins and how its genetic integrity has been sustained over a long period of time, conservatively between 9,000 and 16,000 years old by the latest (2024) estimate. Researchers have argued that Pando's future is uncertain due to a combination of factors including drought, cattle grazing, and fire suppression. In terms of drought, Pando's long-lived nature suggests it has survived droughts that have driven out human societies for centuries at a time. In terms of grazing, a majority of Pando's land mass is fenced for permanent protection and management as a unique tree. Cattle grazing ended in Pando in 2024, but previously, was permitted on a volume basis for 10 days a year in October, weather permitting, in a small edge of Pando's southeastern expanse. Additionally, between 2015 and 2022, the local grazers group, 7-Mile Grazers Association, who rely on Pando's forage and biomass to sustain the landscape, signed off on a long-term protection plan working with Fishlake National Forest and Friends of Pando, and also wrote letters of support for the "Pando Protection Plan", a plan to bring nearly 34 hectares (84 acres) of the tree into protective care. In terms of fire suppression, research indicates Pando has survived fires that would have likely leveled the tree many times, after which Pando regenerated itself from the root system. The same research also indicates large-scale fire events are infrequent, which may be owed to the fact that aspen are water-heavy trees and thus, naturally fire resistant, earning them the name "asbestos forests" among wildfire scientists. Concerns aside, there is a broad consensus that wildlife controls to protect Pando from overbrowsing by deer and elk are critical to its sustainability and care. Protection systems coupled with ongoing monitoring and restoration efforts have been shown to be effective dating back to the late 1980s and early 1990s, with new projects under way. Historically, regeneration rates in portions of the "Aspen Regeneration Project" which started in the 1990s, showed promise based on photographic evidence and repeated survey plots by land managers, scientists and conservation groups between 1993 and today. Despite this, many have argued more work needs to be done to control wildlife, as the Pando Tree is surrounded by 700 square miles of de facto wildlife preserve managed by people, groups and agencies who do not have Pando's sustainability as a central concern in their land management policies. Paul Rogers and Darren McAvoy of Utah State University completed an assessment of Pando's status in 2018 and stressed the importance of reducing herbivory by mule deer and elk as critical to conserving Pando. In 2019, Rogers and Jan Šebesta surveyed other vegetation within Pando besides aspen, finding additional support for their 2018 conclusions and found that interactions between browsing and management strategy may have had adverse effects on Pando's long-term resilience to change. In 2023, a team of researchers, land managers, wildlife biologists and citizen scientists groups began long-term programs to monitor deer and elk using GPS collars and wildlife cameras to better understand wildlife. In 2022, Executive Order 14702 directed the US Forest Service to inventory old growth and mature forest as part of a plan to protect mature and old growth forest. Data submitted by Fishlake National Forest defined Pando's landmass as "mature," meaning it could be eligible for special care and protections. 2024 Pando Protection Plan Between 2015 and 2022, Fishlake National Forest, Pando's federal land stewards, developed a plan and gathered public feedback for work to expand wildlife controls and protections of the Pando Tree as part of the Fishlake Basin Recreation Improvement Plan. Work to develop the plan involved gathering formal and informal feedback from community, regional, and state organizations in Land Management, Agriculture, Conservation, and Recreation between 2015 and 2019, followed by a public comment period which ran from March 2021 through March 2022. The plan was approved in June 2022 by Fishlake National Forest Supervisor Michael Elson. In 2023, Friends of Pando worked to gather letters of support for the plan and was invited by Representative Carl Albrecht to give a brief presentation about the plan to the Utah Legislature.(PDF of Presentation) Based on recommendations and community support, Representative Albrecht secured a $250,000 allocation for the Utah Department of Transportation to develop plans and contract work to expand wildlife controls to bring the majority of Pando's landmass into protective care. Between May 2024 and September 2024, Friends of Pando and community organizations worked to organize a series of talks and meetings to finalize the plan. Based on wildlife behavior data gathered by Friends of Pando, Fishlake National Forest and Utah Division of Wildlife Resources the final plan was mapped to maximize wildlife management in and around the tree. Work was completed in September of 2025. Size and age Most agree, based on Barnes's work and later work, that Pando encompasses 42.89 hectares (106 acres), weighs an estimated 6,000 metric tons (6,600 short tons) or 13.2 million pounds, and features an estimated 47,000 stems, which die individually and are replaced by genetically identical stems that are sent up from the tree's vast root system, a process known as "suckering". The root system is estimated to be several thousand years old, with habitat modeling suggesting a maximum age of 14,000 years and 16,000 years by the latest (2024) estimate. Individual stems do not typically live more than 100–130 years. Pando's landmass spreads from 2,700 m (8,900 ft) above sea level to approximately 2,773 m (9,098 ft) above sea level along the western side of a steep basin wall. Mitton and Grant summarize the development of stems in aspen clones: ... quaking aspen regularly reproduces via a process called suckering. An individual stem can send out lateral roots that, under the right conditions, send up other erect stems; from all above-ground appearances the new stems look just like individual trees. The process is repeated until a whole stand, of what appear to be individual trees, forms. This collection of multiple stems, called ramets, all form one, single, genetic individual, usually termed a clone. Range of age estimates Due to the progressive replacement of stems and roots, the overall age of an aspen clone cannot be determined from tree rings. Speculations on Pando's age have ranged between 80,000 and 1 million years. Many news sources list Pando's age as 80,000 years, but this claim derives from a now-removed National Park Service web page, which redacted that claim in 2023 and was inconsistent with the Forest Service's post ice-age estimate. Glaciers repeatedly formed on the Fish Lake Plateau over the past several hundred thousand years and the mountains above Pando's landmass were crowned by glaciers as recently as the last glacial maximum. Ages greater than approximately 16,000 years therefore require Pando to have survived climate conditions during the Pinedale glaciation, something that appears unlikely under current estimates of Pando's age and modeling of variations in local climate. A 2017 paper by Chen Ding et al. seems to support US Forest Service claims that Pando could not be older than the last Glacial Maximum in the area based on paleo-climate models and genetic traits of aspen sites throughout North America. A 2024 paper indicates the age could be between 16,000 and 80,000 years based on the first somatic mutation model of the tree, but, that research did not complete peer review and also relies on older material and testing methods. Thus, charcoal studies published in 2022 place the lower end of Pando's potential age range at around 9,000 years, while the somatic mutation models' most conservative estimate of 16,000 years of age awaits replication using new material and methods. In addition, any new age claims will need to square their results with climate models to prove conditions were favorable to the Pando seed being able to germinate and establish itself. Estimates of Pando's age have also been influenced by changes in the understanding of the establishment of aspen clones in western North America. Earlier sources argued that germination and successful establishment of aspen on new sites were rare in the last 10,000 years, and that Pando's root system was therefore likely greater than 10,000 years old. More recent observations, however, have shown seedling establishment of new aspen clones is a regular occurrence and can be abundant on sites exposed by wildfire. These findings are summarized in the U.S. Forest Service's Fire Effects Information System: (Charles) Kay documented post-fire quaking aspen seedling establishment following 1986 and 1988 fires in Grand Teton and Yellowstone National Parks, respectively. He found seedlings were concentrated in kettles and other topographic depressions, seeps, springs, lake margins, and burnt-out riparian zones. A few seedlings were widely scattered throughout the burns. In Grand Teton National Park, establishment was greatest (950–2,700 seedlings/ha) in 1989, a wet year, but hundreds to thousands of seedlings established each year despite drought conditions in 1986–1988 and 1990–1991. Seedlings surviving past one season occurred almost exclusively on severely burned surfaces. See also Basal shoot List of oldest trees List of individual trees Rhizome Vegetative reproduction Largest organisms Auxin Cytokinins Posidonia australis References Additional references External links Media related to Pando (tree) at Wikimedia Commons Friends of Pando "A Guide to All Things Pando"