Study finds alpine peaks are greening in Northeast U.S., Canada

Satellite imagery shows the impact of wind above the tree line

Dartmouth College

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Alpine plants, including grass-like sedges and rushes, and low-growing shrubs called heaths, on the rocky summit of Algonquin Peak, located in the Adirondack Mountains in upstate New York. 

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Credit: Photo by Jonathan Chipman.

In northeastern North America, a 500-mile-long stretch of mountains runs from the Adirondacks in New York to the Gaspé Peninsula in eastern Quebec.

Nearly 70 million people live within a day's drive of one of the alpine zones, the area above tree line where trees don't grow due to the harsh conditions.

The ecological habitats, which include the alpine zones in the Green Mountains and the White Mountains, are home to many rare species of flowering plants, making the areas hotspots for biodiversity. However, with climate change and rising temperatures, the alpine zones are impacted by declining snow cover, atmospheric nutrient deposition, and high-impact outdoor recreation where invasive species may be tracked in by hikers, hunters, bikers, skiers, and others enjoying the mountain terrain.

While prior research has examined greening in regions such as the Alps, the Rocky Mountains, and the Arctic, in relation to climate warming and other processes, Jonathan Chipman '90, director of the Citrin Family GIS/Applied Spatial Analysis Laboratory at Dartmouth, noticed that a regional-scale assessment of what's been happening above tree line in northeastern North America was lacking.

Given that Dartmouth is home to remote sensing and technical expertise in processing satellite imagery and time series data, and the Appalachian Mountain Club has a huge amount of alpine ecology expertise on the ground from fieldwork and citizen science projects, Chipman teamed up with co-author Jordon Tourville, a terrestrial ecologist at the Appalachian Mountain Club, to research the topic further.

"This study was a perfect collaboration between a university and a nongovernmental organization in the region, as we don't just want to be doing this research in the abstract, but we want to help land managers, other stakeholders, and the public understand what is happening in the region," says Chipman.

In a new study led by Chipman using hundreds of satellite images over 40 years, the team provides the first regional analysis of greening trends in the northern Appalachian region.

Published in Ecosphere, the results show that 69% of the alpine zones studied have experienced significant increases in vegetation, representing 88% of the alpine area in the region.

"In other regions such as in the Alps, as an area near the top of the mountain warms, the tree line advances, growing higher up the mountain, but the situation here is quite different," Chipman says. "Our results show that significant greening and shrubification, in which alpine plants are being replaced by shrubs, is occurring inside the alpine zone, not just where the tree line is advancing."

This was especially evident for the Presidential Range in New Hampshire and Katahdin in Maine, where greening was prominent within the alpine zone at higher elevations. Increases in vegetation were observed, including in: cliff plants that grow out of rocky outcrops; cushion-tussock, a dense dome-shaped plant; and sedge meadows, a hardy grass-like plant.

However, according to the co-authors, this acceleration of growth may not necessarily be positive if rare alpine plants start getting crowded out by more aggressive flora.

"While these ecological changes are affected by a number of factors—the overall warming trend, the landscape such as the steepness of the slope and sun exposure, snow cover, soil chemistry, and nitrogen deposition from power plant emissions—what's notable in this region is the effect of wind," says Chipman.

All the mountains in the region have very high winds, especially in the winter. Mount Washington, in New Hampshire's White Mountains, has the highest recorded wind speed by a staffed weather station of 231 miles per hour.

"The wind causes the alpine zones to start lower than they would be elsewhere at this latitude," says Chipman. "What we're seeing is that this greening trend on mountains in the Northeast is kind of being held back on the windy side of the mountains, but there's this kind of growth that is being unleashed on the more sheltered sides, where it's occurring faster."

The results show that the region is warming due to climate change, but the observed greening trends don't necessarily match the expected pattern. The researchers suspect that other factors are adding to the impact of warming. "In the late 20th century these mountains were being doused with nitrogen from Midwestern power plant emissions, which acted as a fertilizer for some plant species more than others," says Chipman. "After the 1990 Clean Air Act amendments, these emissions were reduced, but it takes time for the ecosystem to adjust." So climate warming plus other factors makes for a pattern of greening that varies over space and time.

Using Landsat satellite imagery from 1984 to 2024, the researchers defined the alpine zones on every site south of the St. Lawrence River that were large enough to monitor from satellites, which totaled 50 square miles. They identified 35 major alpine zones and modeled the greenness of the landscape over time. They looked at where the greening is occurring regionally and within individual mountains.

One of the challenges of working with satellite imagery from the region is the cloud cover, resulting in fewer clear-sky days for imagery as compared to other regions. Furthermore, given the sparsity of data from the past, this creates the risk for "observation frequency bias," where it may appear as if there's a trend due to the limited amount of older data from the 1980s to 1990s when that may not be the case. To deal with this problem, the team came up with a method that takes every sparse observation in the past and turns it into the best possible predictor of what the data was at that time.

The pilot version of this work was conducted by co-author Irene Ko '27, a Women in Science Project intern in 2024 and a Citrin Lab research assistant from 2024 to 2025, who examined 22 alpine zones, demonstrating that the topic was something to study further.

The co-authors hope that their regional analysis of alpine greening in northeastern North America can be used to help inform future land and ecological management and stewardship practices.

Funding for this research was provided by Dartmouth's Women In Science Program, the William H. Neukom Institute for Computational Science, and the Jeffrey and Rona Citrin family.

Chipman is available for comment at: Jonathan.W.Chipman@dartmouth.edu.

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A color heatmap illustrates the greening rates for

Mount Washington and the Presidential Range in

New Hampshire from 1984 to 2024.

Credit

Illustration by Jonathan Chipman.

Diapensia lapponica, a slow-growing evergreen cushion plant on Mount Washington in New Hampshire's White Mountains, is a cold- and wind-adapted plant found in alpine zones.

 

Credit

Photo by Jonathan Chipman.

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Journal

Ecosphere

DOI

10.1002/ecs2.70765

Article Title

Long-term trends in greenness in the alpine zone of northeastern North America from remote sensing

Article Publication Date

25-Sep-2026

Copying mother: The surprising depth of culture shaping young orangutans’ lives

BAN PALM OIL PLANTATIONS

University of St. Andrews

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A Sumatran orangutan mother and her infant are feeding on vegetation in the forests of Suaq.

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Credit: Guilhem Duvot @ SUAQ Project

New research from the University of St Andrews has found that the amount of knowledge a wild orangutan acquires over its long juvenile development depends on its style of learning, both socially and individually. 

In a paper published today (24 September) in Science, Researchers studying wild orangutans in Sumatra have been able to assess for the first time the scale of learning by juveniles’ before they achieve independence from their mothers. 

Infant orangutans differ greatly from one another in how frequently they engage in social versus individual learning. 

Orangutans hold the record for diligent maternal care, which lasts as long as eight or more years before youngsters can be weaned and forage independently. For orangutans this requires learning the approximately 250 dietary items that need to be extracted from the rainforest, some requiring the use of simple tools.  

 

The new study shows that the scope of the cultural heritage that passes from their doting mother to the infant over these years is substantially greater than has yet been appreciated for any non-human animal. 

  

Researchers from  St Andrews, in collaboration with the Max Planck Institute of Animal Behavior (MPI-AB) in Germany, used long-term data from the Suaq Balimbing monitoring station in Indonesia, and analysed nearly 7,000 records of youngsters’ experiences obtained during 4,700 hours of dawn-to-dusk observations spanning 12 years of field study. 

 

Instances of young orangutans closely peering at details of their mother’s behaviours were recorded as indicators of social learning, and instances in which juveniles explored the world themselves were recorded as indicators of individually driven learning.  

 

Examining how long it took after an episode of attentive peering for juveniles’ own explorations to deviate from the effects of this social information, the surprising answer was that on average it was as long as two and a half hours. This translates into youngsters acquiring 5-6 times more knowledge from their mother and others than their own purely  independent explorations.  

  

This is the first study of cultural inheritance in a wild animal to assess the totality of social and individual learning that goes into achieving the repertoire of behaviour needed for independent adult life. The team found that social and individual learning worked powerfully in tandem to achieve this, with juveniles showing the highest rates of both forms of learning achieving independence with the most comprehensive dietary profiles, in preparation for their adult lives. 

 

Conversely, when both forms of learning were low, individuals ended up with the lowest diet breadth, with a three-fold difference between high and low learning of both forms.  

Co- author Professor Andrew Whiten from the School of Psychology and Neuroscience at  St Andrews, said: “These findings about the extent of cultural and individual learning during these apes’ long childhoods suggest that this pattern, that we clearly share with them, has origins all the way back to our common ancestors, many millions of years ago.”  

The team now plans to look beyond diet breadth to determine whether greater learning also improves energy intake, and ultimately, if this actually translates into survival and reproduction. 

A Sumatran orangutan infant is peering at its mother from a close distance, where the mother is holding a stick tool in her mouth.

Credit

Adriana Luna @ SUAQ Project

A Sumatran orangutan mother and infant pair, with the infant clinging to the mother.

Credit

Eric Balke @ SUAQ Project

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Journal

Science

DOI

10.1126/science.adz6415

Method of Research

Meta-analysis

Subject of Research

Animals

Article Title

How 8 years of social and individual learning interact to shape ecological competence in orangutans

Article Publication Date

24-Sep-2026

Learning style predicts survival skills in young orangutans

How much knowledge a wild orangutan acquires over its long development depends on its tendencies for learning socially and individually

Max Planck Institute of Animal Behavior

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A Sumatran orangutan infant is exploring a Neesia fruit by biting it, holding it, and placing it securely in the space between the trunk and branch of a tree, and then kicking it in an (unsuccessful) attempt to break open the fruit.

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Credit: Zul Zulmaidi @ SUAQ Project

• Orangutans have individual learning styles: over their 8.5-year development, infant orangutans differ from one another in how frequently they engage in social and individual learning.
• Learning style predicts skill development: infants’ social and individual learning tendencies during development predict how many food items they will have learned by the time they become independent from their mothers.
• Learning is more than simply “social” or “individual”: the study shows for the first time that social and individual forms of learning interact to shape broad skill acquisition in wild great apes.

Orangutan infants spend their first eight years with their mothers, and throughout this time, they can draw on her knowledge. After that, however, orangutans are entirely on their own. To fare well as an independent orangutan, infants need to learn many survival skills, and arguably the most important of these are feeding skills. An adult orangutan’s diet constitutes nearly 250 distinct food items, which it chooses from thousands of different options, some of them potentially toxic, in the wide maze of the rainforest. Before they set out on their own, infants must also learn how foods should be processed, and when and where foods can be found in the forest

“How do infants master this complex diet curriculum in those first years?” asks Dr. Revathe Thillaikumar, a Marie Sklodowska-Curie Actions Postdoctoral Fellow at the Max Planck Institute of Animal Behavior.

Humans offer clues. Throughout our evolutionary history, humans had to learn an immense set of skills necessary for survival across many years of development. Many of these skills, such as knowledge of new food sources or hunting techniques, are learnt from one’s culture through a complex interplay of different forms of social and individual learning.

“But until now, whether and how wild animals use different forms of learning to develop their survival-relevant skills have remained unknown,” she says.

In a new study, Thillaikumar and colleagues show that wild orangutans build their broad diet profiles through a similarly fascinating interplay of social and individual learning during infancy. The study, published in Science and led by researchers at the Max Planck Institute of Animal Behavior (MPI-AB) in Germany in collaboration with Universitas Nasional in Indonesia, is the first to show that multiple forms of learning interact over many years to build broad, survival-relevant ecological skills in a wild great ape.

Learning by watching and doing

Researchers agree that many animals need learning to acquire many of the skills necessary for survival in the wild. However, it is debated to what extent animals learn from others (social learning) or practicing themselves (individual learning).

Answering this is challenging, especially in long-lived species like great apes. “To really understand how these forms of learning translate into actual skills and knowledge, we needed to link learning events to concrete, measurable outcomes like diet. But because orangutans develop so slowly, there is a multi-year lag between learning and measurable behavioral change,” says Dr. Caroline Schuppli, senior author of the study and group leader at MPI-AB. 

A detailed dataset

The researchers overcame this challenge by drawing on long-term data from the Suaq Balimbing research station, Gunung Leuser National Park in Indonesia, where an international team of researchers and field assistants follow wild Sumatran orangutans over the course of the animals’ lives. For the study, the team investigated data from 21 immature orangutans recorded from birth to independence at around 8.5 years of age. Across 4,700 hours of observation, they examined three key behaviors: when orangutans closely observed their mother and nearby conspecifics through a behavior called “peering” (a behavioral indicator of social learning); when they explored different items in their habitat (a behavioral indicator of individual learning); and what food items they successfully ate without help from their mothers (a measure of ecological competence).

Thillaikumar worked with theoretical statistician Prof. Paul-Christian Bürkner of TU Dortmund University to analyze just under seven thousand records of social and individual learning, keeping each animal’s history separate to determine how its learning behavior related to its eventual diet breadth. “Analyzing each individual on its own was a linchpin for our study because this allowed us to finally link the two parts that were previously unbridgeable—learning and skill development,” says Thillaikumar.

Two forms of learning

The researchers found that immature orangutans differed substantially in how much they engaged in social versus individual learning. “We were astonished by how different infants were from one another in their tendencies to learn,” adds Thillaikumar. Despite such variation, all immatures engaged in social learning more frequently than individual learning—as much as five times more frequently on average.

 “Learning purely through individual exploration can be risky for a naïve orangutan, especially for immatures who are still growing and cannot afford to miss out on feeding opportunities. So the safer option may be to watch and learn from knowledgeable role models, such as their mothers,” explains Schuppli.

Three-fold contribution of social learning

The team found that when infants engaged in social learning, it triggered subsequent exploration for as long as two-and-a-half hours. “Each time an infant peered, it had a prolonged, ripple effect on subsequent explorations,” says Thillaikumar. The authors wanted to pin down the effects of each of the two processes, so they considered only explorations that were independently initiated to test how individual and social learning worked together.

They found that social learning and individual learning worked in tandem over the developmental period. Infants that engaged in high rates of both forms of learning ended up with the broadest diet profiles at independence. Conversely, when both forms of learning were low, individuals ended up with the lowest diet breadth, with a three-fold difference between high and low learning of both forms.

Increased social learning could even partially compensate for low individual learning by improving diet breadth. “Social learning stepped in to do the heavy lifting, which shows us just how significant it is in the lives of great apes,” adds Thillaikumar.

The results prompt a nuanced appreciation of the mechanisms underlying great ape cultures. “It’s about more than just social or individual learning,” says Schuppli. “It’s about the interplay of complex learning mechanisms that has driven the development of a broad, highly survival-relevant cultural competence in one of our closest, living relatives in the wild. This suggests that the sophisticated cultural learning seen in humans may have deep evolutionary roots.”

Linking learning to survival

The results show that heightened learning results in broader diets, but questions remain about exactly how this advantage arises. “Are they learning about lots of items, or are they getting better at learning?” asks Thillaikumar.

The team now plans to look beyond diet breadth to determine whether greater learning also improves energy intake, and ultimately, if this actually translates into survival and reproduction.

“Questions like these can only be answered by watching animals in their natural environment from birth to death,” says co-author Dr. Sri Suci Utami-Atmoko from Universitas Nasional in Indonesia. “Long-term field studies provide the time and space to follow long-lived animals over their whole histories. For orangutans, these studies provide us with window into how culture and survival have become intertwined over evolutionary time.”

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Journal

Science

DOI

10.1126/science.adz6415

Method of Research

Data/statistical analysis

Subject of Research

Animals

Article Title

How 8 years of social and individual learning interact to shape ecological competence in orangutans

Article Publication Date

24-Sep-2026

Related News Releases

• Learning style predicts survival skills in young orangutans
  (Max Planck Institute of Animal Behavior)

A Sumatran orangutan mother and her infant are feeding on vegetation in the forests of Suaq.

Credit

Guilhem Duvot @ SUAQ Project

Infant peering at its mother using stick tool [VIDEO] | 

A Sumatran orangutan mother is using a stick tool to extract honey from a large tree hole. Her infant is peering at her actions from a close distance, while warding off bees that emerge from the tree hole.

Credit

Guilhem Duvot @ SUAQ Project

Infant peering at its mother eating slow loris [VIDEO] 

A Sumatran orangutan mother is feeding on a dead slow loris and her infant is peering at her while clinging to her.

Credit

Mimi @ SUAQ Project

Infant peering at its mother looking at tree hole [VIDEO] 

A Sumatran orangutan mother is feeding from a tree hole. Her infant is hanging from a branch above her and is peering at her feeding action.

Credit

Lucia Briuscagning @ SUAQ Project

archivehttps://archive.org  › details  › EngelsPartPlayedApeManStudy

Engels’s “The Part Played by Labour in the Transition From Ape...

A 1985 Soviet work. Scanned by a person named I.C.P.

 

Speech shapes dog brains

Dog brains segment speech into words in a way previously seen only in humans

Eötvös Loránd University

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Dog brains segment speech into words in a way previously seen only in humans, a new study from Hungary finds. This suggests that efficient speech processing is not necessarily a consequence of humans’ unique language abilities: regular exposure to speech alone can reshape how the brain functions, even in a mammalian species evolutionarily distant from humans. The discovery by the Neuroethology of Communication Lab at the ELTE Department of Ethology, Budapest was published in Science.

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Credit: Credit: Sarolta Szilágyi

Dog brains segment speech into words in a way previously seen only in humans, a new study from Hungary finds. This suggests that efficient speech processing is not necessarily a consequence of humans’ unique language abilities: regular exposure to speech alone can reshape how the brain functions, even in a mammalian species evolutionarily distant from humans. The discovery by the Neuroethology of Communication Lab at the ELTE Department of Ethology, Budapest was published in Science.

Humans and language have a unique relationship. No other species possesses language abilities as complex as ours, and the human brain is particularly sensitive to the characteristics of speech. But there is a long-standing mystery: do we process speech so efficiently because our brains are inherently built this way, or because we are constantly exposed to speech?

“Words are made up of two main types of speech sounds: vowels and consonants. Although vowels are louder and more noticeable, consonants usually form the skeleton of words. In a continuous speech stream, it is easier to detect individual words when we focus on consonants. And from infancy onward, this is exactly what the human brain tends to do. This phenomenon is known as the consonant bias,” says Attila Andics, cognitive neuroscientist, head of the ERC-funded Neuroethology of Communication Lab, and corresponding author of the study.

“But does the emergence of consonant bias—that is, becoming tuned to speech—require the kind of complex language abilities that are unique to humans? Does it require a brain that is inherently wired differently? Or could tuning to speech arise through simple pattern learning, based on principles also present in other animal species that cannot speak?” asks Andics.

To find out, researchers from the Neuroethology Research Group compared the brain responses of 20 humans and 20 companion dogs to speech. Video abstract of the study.

“We reasoned that if the preference for consonants—the acoustically less salient type of speech sound—requires uniquely human language abilities to develop, then other species should not show such a preference. Not even dogs, despite spending much of their lives surrounded by human speech,” explains Boglárka Morvai, biologist and postdoctoral researcher at the Neuroethology Research Group, co-first author of the study.

“If, on the other hand, tuning to speech is based on simple forms of pattern learning from repeatedly heard speech, then a consonant bias should also emerge in the dog brain—even though such a bias has not previously been found in primate species much more closely related to humans,” Morvai continues.

During the experiment, the human and dog participants listened to continuous, unsegmented speech streams. Consonants and vowels alternated throughout these streams, with no pauses or other acoustic cues separating them. The streams differed in whether they contained recurring patterns and, if so, what kind. There were three types. In the first one, recurring consonant patterns formed consecutive three-syllable words—or, more precisely, word skeletons, because the vowels occurring between the consonants could vary freely. In the second type, the situation was reversed: recurring vowel patterns formed the skeleton of the words. Finally, the third, control type contained no recurring patterns at all, so the syllables did not form words but followed one another in a random order.

To measure brain activity, the researchers used non-invasive EEG, recording the brain’s electrical activity through electrodes placed on the scalp. They also relied on a special neural phenomenon called neural synchronization: our brain activity can take on the rhythm that we detect in the sounds we hear. And the more reliably we detect that rhythm, the more rhythmic the brain response becomes. The researchers expected that if a species’ brain has a preference for consonants, it should follow the rhythm of the words more easily when consonants form the structure of those words.

The results revealed striking similarities between the two species. “In the consonant-structured speech streams, the dog brains, just like the human brains, successfully synchronized with the rhythm of the words. In both species, this synchronization was stronger than in either the vowel-structured or the control streams. This is the first evidence that a consonant bias can also emerge in the brain of a species other than humans,” says Kinga G. Tóth, psychologist, the study’s other co-first author and a doctoral researcher in the group.

The timing of the brain responses provided further evidence for a consonant bias in dogs. Around 400 ms after the beginning of each word, a distinct change appeared in the brain’s electrical activity in both humans and dogs—but only for consonant-structured words. This time window is precisely the one known to reflect the segmentation of continuous speech into individual words.

“The study also revealed that this tuning to the characteristics of speech does not emerge only in dogs that were already living in a speech-rich environment during the first months of life, when they are especially sensitive to social experiences. Dogs that had spent their first three months living on the street or in a shelter, rather than as family pets, showed a similarly strong consonant bias,” G. Tóth adds. “This provides further evidence that consonant bias does not require pre-wired language-processing mechanisms that emerge during a specific early developmental period. Instead, this neural preference may also emerge through relatively simple forms of pattern learning.”

The researchers also observed two interesting differences between the species. First, humans were able to detect words defined by vowel patterns as well, although less successfully than when consonants formed the word structure. Dogs, however, were not. This suggests that when it comes to learning unexpected, non-preferred linguistic patterns, humans may perform better.

The second difference concerned what other rhythms the two species detected in the speech streams. The syllable rhythm appeared in the brain responses of both species, but only the human brain synchronized with the rhythm of the speech sounds. This suggests that the human brain can process continuous speech at a finer resolution: for us, each speech sound is a separate unit, whereas for dogs, syllables form the smallest units of processing.

“Taken together, these findings suggest that the brain's tuning to speech—and specifically the emergence of consonant bias—does not require a pre-wired brain and human-like language abilities,” Andics concludes. “Instead, regular exposure to speech may be enough to change how the brain functions and to give rise to processing characteristics previously observed only in humans—even in a species evolutionarily distant from us.”

 

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Original study:

B. Morvai, K. G. Tóth, M. Boros, D. S. Rácz, I. Iotchev, K. Szabó, A. Andics (2026), Neural evidence that dogs segment the speech they hear with a humanlike consonant bias, Science, doi: 10.1126/science.adw7709

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The research was funded by:

the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (950159); the National Brain Programme of the Hungarian Academy of Sciences (NAP2022-I-3/2022, NAP4-2026-6/2026); the European Union’s Horizon Europe Framework programme under the Marie Skłodowska-Curie Grant Agreement (101168998); the Ministry and Culture of Innovation of Hungary through the National Research, Development and Innovation Fund, financed under the Cooperative Doctoral Program (KDP_2023_ELTE_C2304666), and the Eötvös Loránd University (ELTE).

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Journal

Science

DOI

10.1126/science.adw7709

Article Title

Neural evidence that dogs segment the speech they hear with a humanlike consonant bias

Article Publication Date

24-Sep-2026