New research illuminates the ecological importance of gray wolves in the American West

 

Peer-Reviewed Publication

CONSERVATION BIOLOGY INSTITUTE

 

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A WOLF CHASES MAGPIES AND RAVENS FROM AN ELK CARCASS NEAR SODA BUTTE, YELLOWSTONE NATIONAL PARK

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CREDIT: NPS/JIM PEACO

Corvallis, OR — A study published today in the journal BioScience sheds light on the importance of gray wolves in western United States. Led by William Ripple, a scientist at Oregon State University and the Conservation Biology Institute, the research delves into the implications of large predator absence on plant and animal communities, and ecosystem functions. It calls attention to “shifting baselines” wherein increasingly degraded conditions are viewed as reflecting the historical state of a system.

"By the 1930s, wolves were largely absent from the American West, including its national parks. Most published ecological research from this region occurred after the extirpation of wolves," explains Ripple. "This situation underscores the potential impact of shifting baselines on our understanding of plant community succession, animal community dynamics, and ecosystem functions."

Age structure data for deciduous trees reveal substantial ecological impacts of elk and other ungulates following the removal of gray wolves from Yellowstone, Olympic, and Wind Cave National Parks. This has led to declines in long-term tree recruitment, influencing plant communities and ecological processes.

The study highlights the necessity of characterizing historical context and reference conditions when exploring areas where large predators, like wolves, are either absent, functionally extinct, or persist in reduced densities. The authors note that such areas likely occur in many regions of the world as a result of the widespread loss of large predators. Where applicable, the authors recommend that researchers include a discussion of how the presence or absence of large predators may have influenced their results and conclusions in future ecological studies in national parks.

"In addition to the loss or displacement of large predators, there may be other potential anthropogenic legacies within national parks that should be considered, including fire suppression, invasion by exotic plants and animals, and overgrazing by livestock," adds Dr. Robert Beschta, co-author of the study and emeritus professor at Oregon State University.

To address the effects of predator loss and other potential legacy factors, the study suggests that researchers investigate park archives to exploit historical data and information. National park archives can provide valuable insights into the history of predators and their prey, enabling scientists to discern among competing explanations for shifting ecological baselines.

"Studying altered ecosystems without recognizing how or why the system has changed over time since the absence of a large predator could have serious implications for wildlife management, biodiversity conservation, and ecosystem restoration," emphasizes Ripple.

The research underscores the importance of integrating historical context into ecological studies to provide a more comprehensive understanding of ecosystem dynamics. By acknowledging the historical presence of large predators and other anthropogenic legacies, as well as their potential ecosystem effects, researchers can contribute to more effective conservation and management strategies in national parks and beyond.

Recently, a coalition comprising nearly twelve conservation organizations initiated legal action against the U.S. Fish and Wildlife Service and the U.S. Department of the Interior. Their aim is to reinstate safeguards for gray wolves in Montana and Idaho, contending that the states' forceful hunting strategies endanger these wolf populations.

The research has implications for the long-term conservation of wolves and other large predators, including current gray wolf management and litigation in the West. "We hope our study will be of use to both conservation organizations and government agencies in identifying ecosystem management goals," added Ripple.

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JOURNAL

BioScience

Canada lynx historic range in US likely wider than previously thought

 

Peer-Reviewed Publication

WASHINGTON STATE UNIVERSITY

 

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USING A MODEL VALIDATED BY HISTORIC RECORDS, RESEARCHERS FOUND THAT IN 1900, CANADA LYNX HAD MORE SUITABLE HABITAT IN THE U.S. THAN THE FEW NORTHERN CORNERS OF THE COUNTRY WHERE THEY ARE FOUND CURRENTLY. THE MODEL ALSO HELPED REVEAL MORE POTENTIAL FUTURE HABITAT FOR LYNX IN THE FUTURE: NAMELY IN PARTS OF UTAH, CENTRAL IDAHO AND THE YELLOWSTONE NATIONAL PARK REGION. 

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CREDIT: WASHINGTON STATE UNIVERSITY

 – A broader past could mean a brighter future for Canada lynx in the U.S., according to recent research.

The study, published in the journal Biological Conservation, indicates that lynx might do well in the future in parts of Utah, central Idaho and the Yellowstone National Park region, even considering climate change and the lack of lynx in those areas now.

Using a model validated by historic records, researchers first found that in 1900, Canada lynx had more suitable habitat in the U.S. than the few northern corners of the country where they are found currently. The study showed the elusive big cat likely roamed over a larger area in the Pacific Northwest, Rocky Mountains, Great Lakes region and parts of New England.

“History matters even for wildlife,” said lead author Dan Thornton, a Washington State University wildlife ecologist. “As part of the criteria for species recovery, we have to understand their historic distribution. Otherwise, how can we help recover a species, if we don't know what we’re recovering to?”

Having a more accurate picture of a species’ past can also help avoid an effect known as “shifting baseline syndrome,” Thornton added, which is a gradual change in what people accept as normal for the environment, or specifically in this case, a species’ habitat.

True to their name, Canada lynx are still abundant in Canada, but in the U.S. their numbers have dwindled. Currently, they are only found in limited, northern portions of Washington, Idaho, Montana, Minnesota and Maine. So far, recovery plans for lynx have been based on assumptions that they were never found much beyond these areas in the U.S., although a small population was successfully re-introduced to the Colorado Rockies in 1999.

This study, which has conservation implications for not only lynx but other threatened species, proposes one new way of estimating a species’ historic range, using modelling of suitable habitat validated by historical records.

Thornton and co-author Dennis Murray of Trent University in Canada created the model using factors to determine lynx’s suitable habitat like temperature, precipitation and land use in the last 40 years. They ran that model back in time to 1900 using historic climate and land use data to discover the possible past range, which they validated using records of lynx from museums as well as hunters and trappers who have prized the big cat for its fur.

The researchers then used the model to project suitable habitat into the future of 2050 and 2070. Even when accounting for climate change effects, they found areas that could be good for lynx that fall outside the species’ current range but likely within historically occupied areas: namely in central Idaho, northern Utah and the area in, and around, Yellowstone National Park. Whether or not these areas could support viable lynx populations now or in the future would require additional research, the authors noted.

Conserving lynx as a key predator is important for maintaining the integrity of forest ecosystems, the authors contend, and lynx are an iconic species in the mountains of the Pacific Northwest.

The researchers also hope that this approach to estimating historic range could help inform conservation efforts for other species.

“Thinking about historic range is really important. It’s also quite difficult because we often have limited data on where species were in the past,” Thornton said. “But there are potential ways to go about addressing that, and we wanted to provide one possible approach in this paper.”

This research received support from the U.S. Department of Agriculture’s National Institute of Food and Agriculture.

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JOURNAL

Biological Conservation

Bald eagles eat prairie dogs?

We all know that bald eagles like fish. Few of us, however, picture them soaring over grasslands seeking out prairie dog snacks. In a new paper from the Journal of Raptor Research, lead author Courtney Duchardt and coauthors make the case that prairie dogs are an important resource for at least four species of raptors overwintering in the Southern Great Plains, bald eagles included. Their paper, titled “Overwintering Raptor Abundance and Community Composition in Relation to Prairie Dog Colonies in the Southern Great Plains,” explains the first broad scale look into the relationship between prairie dogs and their aerial predators, and illuminates an important trophic interaction with implications for raptor conservation through the lens of climate change.

 

Grasslands across North America have shrunk significantly since the 1970’s, and for those remaining, habitat quality is a far cry from what it used to be. Since the ‘90’s, the total population of grassland birds across North America has decreased by 53%, illustrating the link between grassland health and bird abundance. Grassland raptors, with their large spatial requirements, likely suffer graver consequences from these reductions in habitat quality than other birds.

 

Duchardt, from the Department of Natural Resource Ecology and Management at Oklahoma State University, and her colleagues, provide strong evidence that the stability and predictability of prairie dog colonies provides an important prey source for overwintering raptors across the Southwest Great Plains. Between 1998 and 2002 the research team conducted winter road surveys in Arizona, Colorado, New Mexico, Texas, and the Mexican state of Chihuahua. Their results were illuminating — nine raptor species occurred in tandem with prairie dog colonies. Notably, bald eagles and rough-legged hawks were included in this pattern, even though they don’t often encounter prairie dogs on their breeding grounds. However, as Duchardt points out, “prairie dogs are perfectly sized raptor-snacks,” so it makes sense that both species would see them as caloric jackpots.

 

Climate change could alter cycles of prairie dog reproduction. Already, variation in climate norms has increased the occurrence of plague among colonial breeding rodents like prairie dogs. If raptors feed on prairie dogs as often as this new study suggests, these shifts in prairie dog availability could push raptors to range further for food. The further they range, the more often they encounter dangers like wind turbines, which have been shown to negatively affect golden eagles and ferruginous hawks. This is of special concern for juvenile raptor which have a hard enough time during their first year of life without added stressors.

 

An obvious next step is to prioritize protection of prairie dog colonies in areas where raptors are associating with them as a prey source. However, supporting prairie dogs for the sake of raptor health is politically tricky. “Prairie dogs are contentious and seen as pests in most parts of their range. However, their role as a keystone species helps to demonstrate that, even though there are conflicts, they are important,” says Duchardt. “To support raptors wintering in the Southern Plains, we need to consider prairie dog management.”

 

Raptors are bioindicators, meaning they serve as proxies for habitat health, and they play a key part in naturally supporting ecosystem functioning as top predators on the landscape. Even with the reality of human-prairie dog conflict, there are pathways forward. “Ranching can be compatible with diverse wildlife communities because many of the wildlife co-evolved with bison, and sustainable ranching can replicate that,” says Duchardt. Using innovative management tools and educating the public on the importance of prairie dogs and raptors in these regions, Duchardt is optimistic that a middle ground can be found — one that allows bald eagles to munch on prairie dogs for years to come.

Yellowstone - wolf pack v bison standoff

 

Final results:

Wolves and elk are (mostly) welcome back

 

In Poland and Germany’s Oder Delta region, survey shows

Survey shows positive attitudes towards rewilding in the Oder Delta region, but finds locals’ feelings are mixed.

Peer-Reviewed Publication

GERMAN CENTRE FOR INTEGRATIVE BIODIVERSITY RESEARCH (IDIV) HALLE-JENA-LEIPZIG

 

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THE ODER DELTA AREA COMPRISES DIVERSE NATURAL HABITATS AND IS PARTICULARLY SUITABLE FOR THE NATURAL COMEBACK OF WILDLIFE.

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CREDIT: SANDEEP SHARMA

An online survey conducted in Germany and Poland shows that large parts of the participants support the return of large carnivores and herbivores, such as wolves and elk, to the Oder Delta region, according to a study published in People and Nature. Presented with different rewilding scenarios, the majority of survey participants showed a preference for land management that leads to the comeback of nature to the most natural state possible. Locals, on the other hand, showed some reservations.

In recent years, the concept of rewilding has captured the attention of conservationists, who see it as a promising and cost-effective tool to combat biodiversity loss and restore ecosystems. The Oder Delta area, which spans the northern border between Germany and Poland, is particularly suitable for the natural comeback of wildlife. It comprises diverse natural habitats, like riparian forests, standing- and flowing waters, open and semi-open inland dunes, and heathlands, and is surrounded by diverse landscapes of forests, rivers, and wetlands.

To measure public sentiment towards rewilding in the Oder Delta, a team of researchers led by the German Centre for Integrative Biodiversity Research (iDiv) and the Martin Luther University Halle-Wittenberg (MLU) carried out an online, choice experiment survey. Given the geographic position of the area across both Germany and Poland, the survey offered a unique opportunity to investigate differences in attitudes between the two countries. Approximately 1,000 respondents from each country were presented with different scenarios describing the ecological status of the Oder Delta in 2050 as a result of various management interventions. The scenarios included, for example, the conditions of rivers and forests and the presence of large animals such as elk, lynx, or wolves. Beyond the “status quo” option, an intensification of land use in the region, respondents were presented with two alternative scenarios with varying biodiversity benefits.

Importantly, only the status quo option came at no additional cost. The two alternative options were associated with tax payments to fund the necessary interventions, meaning that respondents were faced with a trade-off: an increase in nature benefits went hand in hand with an increase in taxes. “This allowed us to calculate the respondents’ willingness to pay for different management interventions in the Oder Delta region”, says lead author Rowan Dunn-Capper from iDiv and MLU. “This helps us understand broader preferences for rewilding”.

Strong preferences for rewilding

The study revealed a significant appetite for rewilding initiatives at the national scale, particularly for the presence of large animals, such as wolves, lynx, elk, and bison in the Oder Delta. Willingness to pay for scenarios in which large animal species were present was almost three times larger than for restoring the most natural landscape elements. “To find such preference was surprising given the often-negative portrayal of large animal species, notably the wolf, in the popular media”, says Dunn-Capper. “It suggests the public may be more welcoming of wildlife return than first thought”. This preference was also true for forests and agriculture: respondents in Germany as well as in Poland had a strong preference for the most natural rewilding levels with minimum human intervention on the ecosystem. Additionally, the fact that results for Germany and Poland were broadly comparable indicates that preferences for rewilding hold across political and cultural contexts.

Locals are less enthusiastic about rewilding

Survey participants living near the Oder Delta (within 100km) did not show the same appetite for rewilding initiatives. Local respondents showed a preference for large herbivores, such as elk and bison, but were less enthusiastic about the presence of large carnivores, like wolves. Similarly, local respondents showed contrasting preferences for certain rewilding interventions in rivers and agricultural landscapes compared to the national sample. For example, a significant share of local respondents were not willing to pay for scenarios in which flooding regimes were fully restored in the Oder Delta. “This underscores the intricacies of conservation planning and highlights the importance of local input to foster biodiversity democracy, this is the management of natural resources as a democratic process”, says senior author Professor Henrique Pereira, head of Biodiversity Conservation at MLU and iDiv. “Generally, our findings support rewilding as a novel ecosystem restoration approach that has public acceptance to become mainstream across Europe.”

Red deer populations in Europe: more influenced by humans than by wolves and other predators

 

Alongside the occasional bison and elk, red deer are Europe's largest native wild animal. An international study led by wildlife ecologists from the University of Freiburg has now investigated the factors that affect the red deer population in a particular area. The researchers were able to show that the population density of the animals in Europe is primarily influenced by human hunting and land use and not by large predators such as wolves, lynx and brown bears. “While large carnivores are often considered key factors in controlling prey populations in undisturbed ecosystems, this is less visible in human-dominated landscapes. Our study illustrates that these interactions are context-dependent,” says Dr. Suzanne T. S. van Beeck Calkoen, former PhD student at the Chair of Wildlife Ecology and Management at the University of Freiburg and first author of the study.

The researchers collected data on the population density of red deer at over 492 study sites in 28 European countries and analysed the influence of various factors such as habitat productivity, the presence of large carnivores, human activities, climatic variables and the protection status of the area. The evaluation of the data showed that human hunting reduced red deer density more than the presence of all large carnivores. Human land use, on the other hand, led to an increase in red deer density. In most cases, the presence of large carnivores had no statistically significant effect on the red deer population. Only when the three predators wolf, lynx and bear occurred together in one area did the number of red deer decrease. However, the study published in the Journal of Applied Ecology did not investigate how the presence of predators affects the behavior of red deer.

The return of the wolf
The study also sheds new light on the ongoing debate about the return of the wolf to Central Europe, notes Prof. Dr. Marco Heurich, Professor of Wildlife Ecology and Conservation Biology at the Faculty of Environment and Natural Resources at the University of Freiburg and initiator of the study. “Our research shows that the return of a large carnivore such as the wolf alone does not have a major impact on the occurrence of red deer. This is because in Central Europe, human influences predominate both indirectly through interventions in the red deer’s habitat and directly through the killing of the animals.” In addition, the mortality rate of wolves in Central European landscapes is very high, mainly due to road traffic, which further limits their influence on prey populations. “However, we also found a high variability in red deer densities, which indicates that there may be specific situations in which large carnivores do have an impact. Investigating this will be the task of future studies,” states Heurich.

Boosting beaver populations could have toxic consequences

 

 

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CLIFFORD ADAMCHAK'S BOAT WITH SAMPLING EQUIPMENT IN A BEAVER POND IN CRESTED BUTTE, COLORADO. 

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CREDIT: CLIFFORD ADAMCHAK/CU BOULDER

Beavers are influential animals in ecosystems. These dam-building, tree-chewing rodents change streamflow with their wooden barriers and create rich wetland habitats by diverting water into soils near rivers. They help conserve water and improve biodiversity. 

But a preliminary study by CU Boulder researchers suggests that beaver activities in the Western U.S. may exacerbate the spread of mercury-containing toxins in rivers and the surrounding habitats. Clifford Adamchak, a Ph.D. student in the Department of Ecology and Evolutionary Biology presented the team’s findings Tuesday at the 2023 meeting of the American Geophysical Union in San Francisco.

“In a world where beavers are increasingly being seen as an effective means to achieve various conservation and restoration goals, there is a possibility that we would see an abnormally large flush of methylmercury if we were to reintroduce beavers in the Western U.S. on a larger scale,” said Adamchak.  “So it is important to better understand the impacts of their activities.”   

Beavers were once ubiquitous in North American streams before Europeans arrived in the region. The animal’s population then plummeted because of hunting and habitat loss. 

Research has shown that beavers change the environment significantly, especially over longer timescales, and can provide various environmental benefits. By building dams and trapping water in their ponds, they help to replenish groundwater supplies and maintain wetland habitats for other species. Beaver ponds also help cool the water and mitigate the spread of wildfires, some increasingly significant benefits as climate change heats up the planet and intensifies wildfires in the Western U.S. As a result, several states, including California, Colorado and Oregon are exploring the idea of releasing more beavers to boost populations.

But beaver ponds, because they lack oxygen, are a hot spot for bacteria that can generate mercury-containing neurotoxins. 

“A stream that flows smoothly with nothing stopping it would have very different biological chemical and geological processes than a stream that has cascading beaver dams and ponds,” said Adamchak. “Beaver activities also impact the surrounding landscape, because the animals forage for woody vegetation on land.” 

Human activities, including coal burning and mining, emit mercury into the atmosphere. The mineral then gets into lakes and streams through rain and snow. In water, chemical reactions and certain bacteria transform the mineral into methylmercury, a toxic organic compound that can build up in organisms and travel down the food chain. For example, when a bear eats a fish containing methylmercury, the neurotoxin will accumulate in the bear’s body. Studies have shown consuming large amounts of methylmercury-containing food can lead to mercury poisoning and nervous system damage in humans. 

While atmospheric mercury levels in the Eastern U.S. have decreased over the years because of emission reduction efforts, the levels in the Western U.S., have remained constant or even slightly elevated. 

Adamchak and the team set off to investigate whether increased beaver activities—partly due to reintroduction efforts—have led to a rise in methylmercury levels in the Western U.S. water. 

Over the past summer, Adamchak visited several beaver ponds in California and Colorado, taking more than 300 samples of water and sediment from the ponds and their surrounding environment. He found that the methylmercury levels in the water of beaver ponds were very low, whereas the levels in the sediment— the soil and sand at the bottom and around the ponds—were very high. This suggests that the toxins might be accumulating in the sediment, rather than the water. 

In addition, Adamchak found that the sediment around the ponds, where water periodically submerges, had the highest methylmercury levels. This implies that beavers could spread the mercury-containing neurotoxin in the surrounding landscape. 

The research is still in its early stages, and Adamchak said it’s unclear to what degree methylmercury can affect the wetland ecosystem as a result of beaver activities. But researchers are concerned that as beavers move around the river corridor across their lifespans and abandon old ponds, more vegetation may grow in areas with high methylmercury concentrations in the soil and get passed on to organisms that feed on them.  

Fortunately, previous studies have shown beaver ponds tend to have higher methylmercury concentrations when they are new, and the levels decrease significantly with age. “That suggests beavers probably don’t have overwhelmingly negative effects on the ecosystem. But at this point it’s very hard to say if more beaver activities are good or bad in terms of mercury levels,” Adamchak said.

Adamchak planned to revisit these ponds next year to collect more data. He will also investigate if the age of the ponds or seasons influence the methylmercury levels in the ponds.