Polar Bears Could Be Struggling to Catch Enough Prey, Study Shows
By Daisy Dunne
Polar bears could be failing to hunt enough seals to meet their energy demands, new research suggests.
A study tracking the behavior of nine female bears from 2014 to 2016 over the Beaufort Sea found that some of the animals exerted so much energy during the hunting season that they lost up to 10 percent of their body mass in an 8-11 day period.
Polar bears live on a diet made up of ringed seals, which they hunt from the ice surface. However, sea-ice cover in the Arctic is falling at a rate of 14 percent per decade. This may be forcing some polar bears to travel further in order to find their prey, the authors of the new research say.
Female bears who lose large amounts of weight during the spring hunting season could find it more difficult to raise their cubs to maturity in the following months, the lead author told Carbon Brief.
However, it is not yet clear how such changes could be affecting the long-term survival of adult polar bears, he added.
Polar bear with a GPS-equipped video camera collar, lying on the sea ice of the Beaufort sea. Anthony Pagano / USGS
Polar bears live across the Arctic and spend the spring and early summer months hunting ringed seals, which provide the animals with a high source of energy and fat.
When autumn arrives, pregnant bears will enter the "denning" season. At this time, females will build themselves a maternity den out of snow, which is where she will give birth to her cubs and nurse them until the following spring.
The research followed the behavior of nine female bears living in the Beaufort Sea area for a period of 8-11 days at some point between 2014 and 2016.
To track the bears' day-to-day activities, the scientists fitted the females with GPS-equipped video-camera collars and accelerometers. They chose to study females because male polar bears' necks are "larger than their heads" and so they are unable to retain collars, according to the research team.
The video-camera collars allowed the researchers to collect a large amount of data, including how far each bears tends to roam across the ice, how much time they spend walking and swimming and how often they come into contact with other bears.
The camera footage also allowed the scientists to observe the techniques bears use when trying to hunt seals. Most of the time, polar bears catch their prey using the "sit-and-wait" tactic, said lead author Anthony Pagano, a PhD candidate at the U.S. Geological Survey (USGS) and the University of California, Santa Cruz. He told Carbon Brief:
"Polar bears walk around until they find a breathing hole that a seal is actively using and they'll typically stay there, they'll either sit down or lay down or stand, and they'll wait at that breathing hole. In some cases, they wait for hours.
"If they detect a seal has come out to breathe, they'll stand up on their hind legs, raise their bodies up into the air and then pounce through the water as a way to try to stun the seal. If they're successful, they'll try to grab the seal around the neck with their jaws and pull them out of the water."
The video below shows the polar bears in action:
In order to collect this data, the researchers had to capture the bears at the start and end of the study period. Catching the bears required the team to track the animals using a helicopter, Pagano said:
"The easiest way to catch the bears is from a helicopter. It's the safest method both for the bears and for the biologists. It's also the best way to try to locate bears as well. Bears occur over a pretty extensive landscape and so locating the bears is a serious challenge."
The recorded field movements of each bear over the two-year study period are shown on the diagram below, where each color represents the movements of one bear. On the diagram, the black bear symbol shows where a bear was captured while the white bear symbol shows where they were recaptured.
Diagram showing the field movement of nine female polar bears in the Beaufort Sea area in April from 2014-2016. On the diagram, the black bear symbol shows where a bear was captured while the white bear symbol shows where they were recaptured. Pagano et al. (2018)
The data collected by the researchers suggest that polar bears are more active than previous research has suggested, Pagano said:
"Previous modellng work has tried to guess what a polar bear's energy expenditure might be and how many seals they might need to capture. They speculated that, because polar bears use the 'sit-and-wait' hunting tactic, they would be able to conserve energy.
"What we found in the study is that the activity rates of these bears are very similar to other terrestrial carnivores, despite this sit-and-wait approach to hunting. They are still quite active and they are still traveling long distances."
In fact, the study finds that polar bears burn energy at a rate that is 1.6 times that of what previous research has suggested.
However, the activity rates of the bears may have been affected by the capturing process, the researchers note in their research paper:
"Admittedly, the activity levels … in the study may be biased low owing to the effects of recovery post-capture. On the basis of movement rate and activity sensor data, recovery post-capture for polar bears may last two to three days."
Using the new estimate, the researchers predicted that a solitary female bear would need to eat, on average, either one adult seal, three subadult seals or 19 newborn seal pups every 10-12 days to gain enough energy to maintain her current weight.
However, in the study period, more than half of the bears did not eat enough seals to meet their energy needs and subsequently lost body mass. Four bears lost more than 10 percent of the 8-11 day study period, with an average loss of 1 percent per day.
Previous research also shows that, in recent years, female bears have been more likely to enter the "denning" season with inadequate fat reserves than in previous years, Pagano said.
The rate of Arctic sea-ice melt over the spring and summer has been increasing in recent decades. Pagano suggests that this could be forcing the bears in the region studied to travel further to find food, and, therefore, be causing them to lose body mass at a faster rate than previously observed. He said:
"In this area, 80-90% of the population is following the ice as it recedes to the north. They're moving much greater distances than they had historically to follow the ice as it retreats hundreds of kilometres further to the north than it did historically.
"Once the ice returns in the fall and the winter, they're following the ice back and making a long distance migration back to areas that are thought to have a higher variability of seals."
Losing weight during the spring months could leave female bears without the adequate resources needed to raise their young in the "denning season," Pagano said, which could be causing declines in cub survival:
"Some work has shown that they are emerging from their dens in lower body condition and they are not able to locate as much food as they have done historically. Basically, they're not able to provide for their young at an adequate level and that's driving declines in cub survival."
The threats facing polar bears in this region are likely to worsen as climate change continues, he said:
"The concern is that as the ice breaks up earlier each year, the bears will be impacted in three ways: they'll be less successful at catching seals because they're being displaced from their primary foraging habitat earlier; they're putting on less weight than they would have done historically; and then they're also moving greater differences. If that trend continues, we would expect continued declines in reproductive success."
However, it is less clear how these changes could impact the survival rates of adult bears, he added:
"From what we've seen so far there doesn't seem to be large decreases in adult survival, it really seems to be a function of females to be able to produce offspring and successfully raise them."
Research from the International Union for the Conservation of Nature (IUCN) polar bear specialist group shows that polar bear populations in the southern Beaufort Sea are "likely to decline" in the future. Carbon Brief has previously published an article examining how climate change could affect polar bear population numbers.
Polar bear wearing a video camera collar, hunting for seals on the sea ice of the Beaufort sea. Anthony Pagano / USGS
The findings could tell scientists more about how "polar bears are responding to climate change," said Prof. Charlotte Lindqvist, a biologist from the University at Buffalo in New York, who was not involved in the research. She told Carbon Brief:
"The sample size is small, but what can you do when you sample rare and wild polar bears on the sea ice? If half of the studied bears are already showing signs of energy deficiency on the spring sea ice, we can only imagine a likely gloomy outlook for polar bears as sea ice continues to decline."
The "major strength" of the research comes from the integration of several different methods to gain greater insight into the behavior of polar bears, said Prof. Andrew Derocher, a polar bear biologist from the University of Alberta, who was not involved in the current study. He told Carbon Brief:
"One challenge with the study findings is that we know that feeding varies widely over space and time with polar bears and the study period used was, by necessity, quite brief. Some of the results could be rather different a few weeks or a month later. However, none of this detracts from the study's findings, but context is useful."
The research highlights that the challenges facing polar bears are "complex" and scientists are "yet to fully understand them," he added:
"Arctic sea-ice loss is a global issue and there is no quick fix: no protected areas, no habitat modification, or other standard conservation approach could significantly alter the threats facing polar bears in a warming climate. Only the reduction of greenhouse gases can slow the rate of loss of polar bear habitat and improve the conservation outlook for the bears."
Reposted with permission from our media associate Carbon Brief.
EcoWatch Daily Newsletter
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What Is PTSD?<p><a href="https://theconversation.com/veterans-refugees-and-victims-of-war-crimes-are-all-vulnerable-to-ptsd-130144" target="_blank">PTSD</a> can occur when someone is exposed to extreme exposure traumatic experience. Typically, the trauma involves a threat of death, serious injury, or sexual violence. Along with war veterans, it happens to refugees; to victims of gun violence, rape and other physical assaults; and to survivors of car accidents and natural disasters like earthquakes or tornadoes.</p><p>PTSD can also happen by witnessing trauma or its aftermath, often the case with <a href="https://www.psychiatry.org/patients-families/ptsd/what-is-ptsd" target="_blank">first responders</a> and <a href="https://www.psychologytoday.com/us/blog/the-many-faces-anxiety-and-trauma/202006/invisible-wounds-the-frontline-heroes" target="_blank">front-line workers</a>.</p><p>All this adds up to tens of millions of Americans. Up to 30% of combat veterans and first responders, and 8% of civilians, <a href="https://www.ptsd.va.gov/professional/treat/essentials/epidemiology.asp" target="_blank">fulfill the diagnostic criteria for PTSD</a>. And that criteria is not easily met: symptoms of PTSD include nightmares, flashbacks, intrusive trauma memories, difficulty sleeping, avoidance of reminders of trauma, negative emotions, and what we call "hyperarousal symptoms."</p>
Fireworks Can Trigger Flashbacks<p>Hyperarousal, a core component of PTSD, occurs when a person is hyper-alert to any sign of threat – constantly on edge, easily startled and continuously screening the environment.</p><p>Imagine, for instance, stepping down the stairs in the dark after hearing a noise; you're worried an intruder might be downstairs. Then a totally unpredictable loud sound explodes right outside your window.</p><p>For people with PTSD, that sound – reminiscent of gunfire, a thunderstorm or a car crash – <a href="https://theconversation.com/veterans-refugees-and-victims-of-war-crimes-are-all-vulnerable-to-ptsd-130144" target="_blank">can cause</a> a panic attack or trigger flashbacks, a sensory experience that makes it seem as if the old trauma is happening here and now. Flashbacks can be so severe that combat veterans may suddenly drop to the ground, the same way they would when an explosion took place in combat. Later, the experience can trigger nightmares, insomnia or worsening of other PTSD symptoms.</p><p>Those of us who set off fireworks need to ask ourselves: Are those few minutes of fun worth the hours, days, or weeks of torment that will begin for some of our friends and neighbors – including many who put their lives on the line to protect us?</p>
Who Else Is Affected?<p>Millions of others, though not diagnosed with PTSD, may similarly be affected by fireworks. <a href="https://adaa.org/about-adaa/press-room/facts-statistics" target="_blank">One in five Americans</a> have an anxiety disorder, many with symptoms of hyperarousal. Also impacted are those with autism or developmental disabilities; they find it difficult to cope with the noise, or just the drastic change from life routines. Then there are people who have to work, holiday or not: nurses, physicians and first responders, who have to be up at 4 a.m. for a 30-hour shift.</p><h3>How to Reduce the Negative Impact</h3><p>There are ways to reduce how fireworks affect others:</p><ul><li>For those with PTSD, the unexpected nature of fireworks is probably the worst part. So at least make it as predictable as possible. Do it in designated areas during designated times. Don't explode one, for instance, two hours after the designated time window. And avoid setting them off <a href="https://www.theguardian.com/society/2018/jul/04/fireworks-ptsd-fourth-of-july-veterans-shooting-survivors" target="_blank">on the 3rd</a>. People are less prepared then.</li><li>If you're aware that a veteran or trauma survivor lives in the neighborhood, move the noise as far as possible from their home and give them prior warning. Consider putting a sign in your front yard noting the time you'll set the fireworks.</li><li>Remember, it doesn't have to be super loud to make it fun. Consider using <a href="https://thehill.com/opinion/energy-environment/504964-its-time-for-silent-fireworks" target="_blank">silent fireworks</a>. And you don't have to be the one who lights the fireworks. Simply enjoy watching while your city or township does it safely.</li></ul>
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By Jeff Berardelli
For the past year, some of the most up-to-date computer models from the world's top climate modeling groups have been "running hot" – projecting that global warming may be even more extreme than earlier thought. Data from some of the model runs has been confounding scientists because it challenges decades of consistent projections.
International Effort to Evaluate Climate Models<p>For the past 25 years the international community has been evaluating and comparing the world's most sophisticated climate models produced by various teams at universities, research centers, and government agencies. The effort is organized by the World Climate Research Programme under the United Nations World Meteorological Organization.</p><p>Climate models are complicated computer programs composed of millions of lines of code that calculate the physical properties and interactions between the main climate forces like the atmosphere, oceans, and solar input. But models also go a lot further, incorporating other systems like ice sheets, forests, and the biosphere, to name a few. The models are then used to simulate the real-world climate system and project how certain changes, like added pollution or land-use changes, will alter the climate.</p><p>Every few years there is a new comprehensive international evaluation called the Coupled Model Intercomparison Project (CMIP). In the sixth such effort, known as CMIP6 and now under way, experts are reviewing about 100 models.</p><p>Information gleaned from this effort will act as a scientific foundation for the U.N.'s Intergovernmental Panel on Climate Change (IPCC) next major assessment report, scheduled for release in 2021. The goal of the report – the sixth in 30 years – is to inform the international community about how much the climate has changed, and, importantly, how much change can be expected in coming decades.</p>
A Conundrum Emerges<p>Over the past year, the CMIP6 collection of models being reviewed threw researchers an unexpected curveball: a significant number of the climate model runs showed substantially more global warming than previous model versions had projected. If accurate, the international climate goals would be nearly impossible to achieve, and there would be significantly more extreme impacts worldwide.</p><p>A foundational experiment in every report addresses "sensitivity": If you double levels of carbon dioxide (CO2) that were in the air before the Industrial Revolution, how much warming do the models show? This doubling is not expected for a few more decades, but it is a quick way to communicate the critical role of greenhouse gases in changing the climate.</p><p>The amount of CO2 in the atmosphere has increased by 35% since the 1800s because of the burning of fossil fuels. As a result, global temperatures have already increased by more than 2 degrees Fahrenheit.</p><p>In the first IPCC assessment report, published in 1990, the answer to that question about the impact of doubling carbon dioxide gave a fairly wide range of results – between 2.7-8 degrees F of global warming. Since then, four more assessments issued six to seven years apart reached nearly the exact same conclusion on sensitivity.</p><p>But that sensitivity may, for the first time, change significantly in next year's assessment. Why? Because starting last year, numerous models in the CMIP6 collection displayed even bigger spikes in temperature upon doubling of CO2 concentrations. We're in serious trouble if the climate sensitivity falls in the mid or upper range of the previous assessments. But if the new, higher estimates are correct, the impacts on civilization would be catastrophic.</p>
In the above CarbonBrief interactive visualization, the bars offer a comparison in the range of sensitivity in the CMIP5 models (gray) and CMIP6 models (blue).
New and Encouraging Evidence Is Emerging<p>At first, scientists were uncertain whether the new model runs were on to something, so the international modeling community dug in to produce multiple studies. The results are not yet conclusive, but a gradual collective sigh of relief seems to be materializing.</p><p>"Evidence is emerging from multiple directions that the models which show the greatest warming in the CMIP6 ensemble are likely too warm," explains Dr. Gavin Schmidt, director of NASA's Goddard Institute for Space Studies.</p><p>For example, <a href="https://www.earth-syst-dynam-discuss.net/esd-2020-23/" target="_blank">a study</a> released April 28 evaluated the past performance of the models making up the CMIP6 ensemble. The team assigned weights to each model based upon historical performance of their warming projections, weighing the poorer performing models less. By doing so, both the mean warming and the range of warming scenarios in the CMIP6 ensemble decreased, meaning the warmest models were the ones with weaker historical performance. This result supports a finding that a subset of the models are too warm.</p><p>That conclusion is supported by another new study evaluating one particular model – the Community Earth System Model (CESM2) – that showed greater warming. Using that model, the researchers simulated the climate in the early Eocene era, about 50 million years ago, when rainforests thrived in the Arctic and Antarctic. The CESM2 simulated a historical climate that seems way too warm compared with what is known about that era from geological data, indicating that the model is likely also too warm in its future projections.</p><p>Two other recent studies of the CMIP6 models being evaluated use clever analysis methods to <a href="https://www.google.com/url?q=https://www.earth-syst-dynam-discuss.net/esd-2019-86/&sa=D&ust=1589209938203000&usg=AFQjCNHYwFB-1KqndGfJ4sXdrrm9DpbLaQ" target="_blank">narrow the range</a> of future warming projections and also <a href="https://www.google.com/url?q=https://advances.sciencemag.org/content/6/12/eaaz9549&sa=D&ust=1589209938203000&usg=AFQjCNEhKY1YZ19qgjSZ_hJM14JmzqXOXw" target="_blank">reduce the projected warming</a> of the CMIP6 models by 10 to 15%.</p><p>Through the intensive research spurred by the CMIP6 climate-sensitivity curveball, scientists have been able to turn a confounding challenge into a confidence builder, providing even greater certainty than they had before in both the abilities of the climate science community and in the computer models used. Moreover, the experience has helped unearth uncertainties remaining in the modeling process.</p><p>Experts conclude much of this uncertainty probably lies in the complexity of clouds. "We have been looking as a community at why the models with greater warming are doing what they are doing – and it's tied to cloud feedbacks in the southern mid-latitudes mostly," explains Schmidt.</p><p>In fact, <a href="https://advances.sciencemag.org/content/6/26/eaba1981" target="_blank">a new study</a> addressing the increased sensitivity was published in Science Advances stating, "Cloud feedbacks and cloud-aerosol interactions are the most likely contributors to the high values and increased range of ECS [sensitivity] in CMIP6."</p>
Understanding the Complexity of Clouds<p>It's long been known in climate modeling circles that cloud processes and interactions are a potential weak link for climate modeling. That reality has been brought front and center by the urgent challenges posed during this CMIP6 evaluation period, but the current evaluation of models also provides an opportunity for discovery and improvement.</p><p>Cloud complexity comes from the reality that clouds have a multitude of sizes, altitudes, and textures. Some clouds cool Earth by providing shade, reflecting sunlight back into space. Others act like a blanket, trapping heat and warming the world.</p><p>Given that about <a href="https://www.nasa.gov/vision/earth/lookingatearth/icesat_light.html" target="_blank">70% of the globe</a> is covered by clouds at any given time, it's no surprise that they play an integral role in regulating the climate. The challenge is to figure out which types of clouds will increase, which will decrease, and what the net effect will be on cooling or warming as the climate changes.</p><p><a href="https://www.nature.com/articles/s41561-019-0310-1" target="_blank">One study</a> last year reached an alarming conclusion: Left unchecked, the release of CO2 into the atmosphere may lead to a tipping point where shallow low clouds disappear – leading to runaway, catastrophic warming of nearly 15 degrees F. While scientists see that outcome as only a remote possibility, it drives home the urgent need to better understand clouds.</p><p>"We have a saying at NOAA: It isn't rocket science – it's much, much harder than that," quips Dr. Chris Fairall, ATOMIC's lead investigator. "One of the major problems for modeling is there is not clean separation of scales." The photo below is one that Fairall took from the NOAA P-3 aircraft.</p>
Investigating the Secrets of Clouds<p>To address the urgent question about the dynamics and role of clouds in a warming world, NOAA and European partners launched their ongoing research effort unprecedented in scale. The U.S. contribution, ATOMIC – short for Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign – is an international science mission that was featured recently on "<a href="https://www.cbsnews.com/video/study-aims-to-examine-links-between-climate-change-and-clouds/" target="_blank">CBS This Morning: Saturday</a>."</p>
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