Biodiversity Climate Change Trees & Forests

Forest Regeneration

This post explores new research on the critters, including humans, who help shape forests.

White pine and maple at Britannia Beach, Ottawa. Photo by R. Last.

Meet the Mice Who Make the Forest

A deer mouse, temporarily captured for a behavioral test before being rereleased to the grounds of a study site at the University of Maine in late October. Photograph by Tristan Spinski.

Brandon Keim wrote a fascinating article in the New York Times about research that is exploring the role of small mammals in tree seed dispersal. Ivy Yen, a biologist at the University of Maine, uses fluorescent markers on seeds to study how deer mice and voles move these seeds across landscapes. Her focus is specifically on the role that the animals’ personalities play in their willingness to move seeds. If one is interested in the future of a forest — which tree species will thrive and which will diminish, or whether those threatened by a fast-changing climate will successfully migrate to newly hospitable lands — one should look to these seed-dispersing animals. “The only way they’re (trees) going to move with the shifting temperatures is with the animals,” Ms. Yen said of the trees. “Will personality affect that? Will there be individuals who are more likely to help?”

Ms. Yen is a doctoral student in the lab of Alessio Mortelliti, a wildlife ecologist with a peculiar interest: how seed dispersal intersected with the emerging study of animal personality. Each summer for the past seven years, Dr. Mortelliti’s students trap deer mice and southern red-backed voles in their study plots — about 2,000 animals in all — and test them to measure where they fall on a spectrum between bold and shy. Before being released, each is tagged with a microchip like those used to identify lost pets.

Over the years, Mortelliti’s teams have developed intricate protocols for tracking the small mammals and determining what they do with different species of tree seed. Acorns are especially useful because they can be easily marked and discovered from wherever the animals hide them. Many seeds will be eaten, of course, but some will stay hidden, eventually growing into new trees.

The work has produced numerous papers, but one published in Ecology Letters, Dr. Mortelliti describes as a “proof of concept”. The researchers showed that the personalities of small mammals influence their choice of seeds. Earlier this year the team described how some deer mice, depending on their personality, were more likely than others to cache red oak, white pine and American beech nuts in ways that promoted germination.

This fascinating article is lushly illustrated by Tristan Spinski’s gorgeous photographs.

Carmela Buono, a PhD candidate in biological sciences, photographed at the Nature Preserve, Thursday, March 31, 2022. Credit: Jonathan Cohen.

The role of ants in forest regeneration

Walk through an old-growth forest in early spring, and you’ll be dazzled by wildflowers, their jewel-like tones shining from the forest floor. But in newer forests, spring ephemerals such as trillium, wild ginger, violets and bloodroot are in shorter supply. The reason may lie with some less-flashy forest residents: Aphaenogaster sp., or the woodland ant. “Not a lot of people have heard of them, but they are the powerhouse of moving seeds and called ‘keystone dispersers,'” explained Carmela Buono, a Binghamton University doctoral candidate in biological sciences. Buono is the lead author of a paper recently published in Ecology that measured understory plants and seed dispersal by ants in 20 New York state forests, half old-growth and half-regenerated. More than 95% of New York state forests—including the Binghamton University Nature Preserve—are secondary forests, which have sprung up on land once cleared for agriculture. While parts of these regenerated forests, such as the overstory, have recovered well, they are missing other aspects of biodiversity—particularly when it comes to understory plants such as native wildflowers. Many plant species rely on a mutual relationship with ants to disperse their seeds. In fact, northeastern North America is one of the major hotspots of ant-plant mutualism. “These plants evolved with seeds that have an appendage rich in fats attached to them, and that’s very attractive to woodland ants,” she said. “Ants need fats just as much as protein and sugar, and it’s hard to find foods rich in fats in the forest. Ants are beneficial. They’re not as charismatic as butterflies or bees that help pollinate flowers, but they are just as important,” Buono said.

Credit: Pixabay/CC0 Public Domain

How humans shape global forests

Climate change and human activities strongly influence forests, but researchers have not fully understood the pervasiveness of these stressors and how they will shape future forest structure. Forests are expected to be mostly intact in protected areas (PAs) and so-called intact forest landscapes (IFLs). However, human impacts are expanding and intensifying to affect even these areas, and the global importance of such effects remains poorly understood. Now, researchers led by Dr. Li Wang from the Aerospace Information Research Institute (AIR) of the Chinese Academy of Sciences (CAS) have provided, for the first time, a panoramic view of global patterns in the multidimensional structure of forests. As part of their work, the researchers have discerned the relative importance of climate and human impacts as well as other environmental factors in shaping global forest structure, particularly that of PAs and IFLs. The study was published in Nature Sustainability.

Indigenous Knowledge Trees & Forests

2023 February Indigenous Plant Wisdom

Image from BC Greenhouse Builders.

An Indigenous reservation has a novel way to grow food – below the earth’s surface

A fascinating article by Hallie Golden highlights how members of the Oglala Sioux Tribe in South Dakota are improving food security and community resilience in the face of climate change. Underground greenhouses, called walipini are helping the people to take back control of their nutrition and ease farming amid the climate crisis, which has seen floods, high winds and hailstorms destroy outdoor crops and regular greenhouses. See also, this earlier article from the BBC about similar technologies being used in Bolivia: Farming underground in a fight against climate change.

A new study led by SMU suggests “cultural burning” could potentially weaken the role of climate in triggering today’s wildfires. Credit: Chris Guiterman

For 400 years, Indigenous tribes buffered climate’s impact on wildfires in the American Southwest

Adding to a growing body of evidence, new research from Southern Methodist University suggests bringing “good fire” back to the U.S. and other wildfire fire-prone areas, as Native Americans once did, could potentially blunt the role of climate in triggering today’s wildfires. The age-old Native American tradition of “cultural burning” appears to have previously weakened—though not entirely eliminated—the link between climate conditions and fire activity for roughly 400 years in the southwestern United States. Studying a network of 4,824 fire-scarred trees in Arizona and New Mexico, where the Apache, Navajo and Jemez tribes lived, SMU fire anthropologist Christopher Roos and other researchers found that the typical climate-fire pattern from 1500 to 1900 reflected one to three years of above-average rainfall—allowing vegetation to grow—followed by a fire-fueling year of significant drought. But the pattern was broken when Native American tribes performed traditional burning practices, according to the group’s study published in Science Advances.

See also:

Credit: Unsplash/CC0 Public Domain

Forests in protected Indigenous lands are healthier, scientists find

Over the last two centuries, human actions have resulted in rising temperatures, a massive carbon imbalance, and tremendous biodiversity loss. However, there are cases in which human stewardship seems to help remediate this damage. Researchers publishing in the journal Current Biology examined tropical forests across Asia, Africa and the Americas and found that the forests located on protected Indigenous lands were the healthiest, highest functioning, most diverse, and most ecologically resilient. Understanding how Indigenous management leads to better outcomes is key to a more equitable approach to conservation. Sze hopes that she and her colleagues can continue to understand how Indigenous land rights and management fit into our conservation policy. “My research is very much inspired by what decolonial climate movements are trying to achieve, in trying to have Indigenous communities and local communities have more autonomy over these spaces,” she says.

Arborist Steve Houser examines the California Crossing tree, a pecan with a bent trunk that points to a low-water crossing in Dallas. Photo by: Michael Amador.

If These Trees Could Talk

No historical marker indicates that this particular pecan tree near the grounds of the Texas National Guard Armory in northwest Dallas is special—just the fact that its trunk grows along the ground for about 25 feet before turning upward. Sometimes natural forces, such as ice storms, can bend trees into strange shapes like this. But for this pecan, its shape is no accident. Steve Houser, a local arborist and founding member of the Texas Historic Tree Coalition, traces his fingers over scars on the tree’s trunk, signs indicating humans may have lashed down the trunk with yucca rope some 150 years ago, when it was a flexible sapling. The bent tree, known as the California Crossing marker tree, points to a low-water crossing on the Elm Fork of the Trinity River, offering valuable information to those who would have recognized it as a marker tree. “The typical settler would go right by,” says Houser, chairman of the coalition’s Indian Marker Tree Committee. “A Comanche would see it and follow it. Trees told them where to go to.” He has been studying marker trees for more than 20 years and last year released a book on the topic, Comanche Marker Trees of Texas, co-authored with Jimmy W. Arterberry, the Comanche Nation tribal administrator, and Linda Pelon, a Waco anthropologist. With the extra publicity of the book, members of the public have come forward with many more posibilities. Houser now has a list of 176 potential marker trees. The article goes on to note that marker trees must be at least 150 years old, are usually long-lived native species, like bur oaks or pecans, and may be scarred where they were deliberately altered or tied down. The presence of arrowheads near the trees can help to bolster the case.

Health Trees & Forests

Giant Steps

Photo by R. Last.

Giant steps: why walking in nature is good for mind, body and soul: Studies of walking’s benefits date back to the 1950s, with the last decade of research preoccupied with the rise of “10,000 steps a day” challenges and the use of pedometers and activity trackers. What they tell us is that while all these tools urge us towards lofty step counts, there isn’t exactly a magic number to achieve. The figure 10,000 was dreamed up as part of a 1960s pedometer marketing campaign in Japan, and a recent study indicates that half that amount can be beneficial, with a plateau in benefits after about 7,500 steps. The NHS advises that just 10 minutes of brisk walking daily makes a difference. For an activity many of us do daily without thinking, this seems remarkable, but it’s estimated that when walking over half our body’s muscle mass is engaged. And the benefits of even a moderate pace – around three miles an hour – range from improved cardiovascular health, like lower blood pressure, to better glucose metabolism, musculoskeletal health, and mental wellbeing. However, researchers distinguish between the passive steps we take going about our lives doing things like food shopping and errands (termed “secondary purpose walking”) and the act of actually going for a walk, which was the thing I really missed. On a walk, when we’ve laced our boots a bit more intentionally, the benefits reach beyond a bit of exercise, and where we choose to walk can make a big difference. There is a growing swathe of research to back up the idea that being in nature improves not simply mental but physical health. Most studies highlight a 1984 study by Roger Ulrich, a professor of healthcare architecture who examined whether hospital patients with a view of nature recovered faster, and better, than those who didn’t. But as the contemporary American philosopher, Arnold Berleant, argues, it is when we’re actually moving through a landscape, rather than treating it simply as scenery, that we most fully connect with a place and ignite all our senses. Berleant uses the term “aesthetic engagement”, but it needn’t be quite so lofty: A walk along the river might count, or perhaps time spent practising shinrin-yoku (forest bathing), really attending to the details of the trees, the leaves, the smells and the sounds. Over the past 20 years, research into the benefits of this kind of outdoor exercise has boomed: looking at the impact of, say, free gyms in parks or the improvement to learning outcomes for students walking in the woods. In one of the earliest studies, researchers in 2005 found that while walking or jogging improved blood pressure and mental health, viewing pleasant rural and urban scenes while doing so had a better impact on wider health and self-esteem than exercising on its own.

Climate Change Trees & Forests

Old Trees & Climate Change

Credit: Pixabay/CC0 Public Domain

Protecting very old trees can help mitigate climate change: Ancient trees—those that are many hundreds, or even thousands, of years old—play a vital role in biodiversity and ecosystem preservation by providing stability, strength, and protection to at-risk environments. In a review article publishing in Trends in Ecology & Evolution, a team of ecologists highlight the importance of preserving these monumental organisms and present a project initiative to ensure their protection and longevity. “Ancient trees are unique habitats for the conservation of threatened species because they can resist and buffer climate warming,” write the authors, including Gianluca Piovesan and Charles H. Cannon. Some of these trees, such as bristlecone pines in the White Mountains, U.S., can live up to 5,000 years and act as massive carbon storage. Ancient trees are hotspots for mycorrhizal connectivity, the symbiotic relationship with underground fungi that supplies plants with many of the nutrients they need to survive. This symbiosis with fungi also helps reduce drought in dry environments. Ancient trees play a disproportionately large role in conservation planning and yet are being lost globally at an alarming rate. The researchers propose a two-pronged approach to protect ancient trees: first, the conservation of these trees through the propagation and preservation of the germplasm and meristematic tissue from these ancient trees, and second, a planned integration of complete protection and forest rewilding.

Trees & Forests

Talking Trees?

Are Trees Talking Underground? For Scientists, It’s in Dispute: This lengthy article examines the claims of a wood-wide web – the popularized term that posits trees share resources via mycorrhizal networks. While no one disputes the existence of the mycorrhizal networks, several alternative theories are proposed. For example, mycorrhizae may be sharing resources strictly for their own benefit, with ancillary benefits for trees. Resource sharing may have nothing to do with so-called communication between trees. Mycorrhizal resource-sharing may not be widespread as it has only been documented in a few forest networks. In many studies, the putative networks appeared to either hinder tree growth or to have no effect. No one has demonstrated that fungi distribute meaningful amounts of resources among trees in ways that increase the fitness of the receiving trees. The article is presents both sides of the argument, citing key scientists on both sides and highlighting where additional research is required to prove the argument one way or another.

Melanie Jones, a biologist at the University of British Columbia, Okanagan, examines a forested area of her campus. Dr. Jones and her colleagues are part of a skeptical reaction to the theory of the “wood-wide web.” Photo credit…Jennilee Marigomen for The New York Times
Garden Reading Trees & Forests


What the World Will Lose if Ancient Trees Die Out: Old trees are in big trouble. Whole forests with fire-resistant giant sequoias up to 3,000 years in age have recently gone up in flames. Whole stands of drought-resistant Great Basin bristlecone pine, a species that can reach 5,000 years in age, have been sucked dry by bark beetles. Monumental baobabs, the longest-living flowering plants, buckle under the stress of drought in southern Africa. The iconic cedars of Mount Lebanon, ancient symbols of longevity, struggle in warmer, drier conditions. Millennial kauris in New Zealand and centenarian olive trees in Italy succumb to invasive diseases. Cumulatively, this is more than a cyclical turnover. This is a great diminution: fewer megaflora (massive trees), fewer elderflora (ancient trees), fewer old-growth forests, fewer ancient species, fewer species overall. Although Earth’s “tree cover” — three trillion plants covering roughly 30% of all land — has expanded of late, It’s young stuff. Old-growth communities are scarce and getting scarcer. Ancient trees are gift givers. They inspire long-term thinking and encourage us to be sapient. They engage our deepest faculties: to revere, analyze and meditate. If we can recognize how they call upon our ethical imperative to care for them, then we should slow down climate change now, and pay forward to people who will need a future planet with chronodiversity as well as biodiversity. The author of this thoughtful article is Jared Farmer, a professor of history at the University of Pennsylvania and the author of “Elderflora: A Modern History of Ancient Trees.”