Insects, reptiles, fish and plants migrating north as winter freezes in South become less frequent
Notwithstanding last month’s cold snap in Texas and Louisiana, climate change is leading to warmer winter weather throughout the southern U.S., creating a golden opportunity for many tropical plants and animals to move north, according to a new study appearing this week in the journal Global Change Biology.
Some of these species may be welcomed, such as sea turtles and the Florida manatee, which are expanding their ranges northward along the Atlantic Coast. Others, like the invasive Burmese python — in the Florida Everglades, the largest measured 18 feet, end-to-end –maybe less so.
Equally unwelcome, and among the quickest to spread into warming areas, are the insects, including mosquitoes that carry diseases such as West Nile virus, Zika, dengue and yellow fever, and beetles that destroy native trees.
“Quite a few mosquito species are expanding northward, as well as a lot of forestry pests: bark beetles, the southern mountain pine beetle,” said Caroline Williams, associate professor of integrative biology at the University of California, Berkeley, and a co-author of the paper. “In our study, we were really focusing on that boundary in the U.S. where we get that quick tropical-temperate transition. Changes in winter conditions are one of the major, if not the major, drivers of shifting distributions.”
That transition zone, northward of which freezes occur every winter, has always been a barrier to species that evolved in more stable temperatures, said Williams, who specializes in insect metabolism — in particular, how winter freezes and snow affect the survival of species.
“For the vast majority of organisms, if they freeze, they die,” she said. “Cold snaps like the recent one in Texas might not happen for 30 or 50 or even 100 years, and then you see these widespread mortality events where tropical species that have been creeping northward are suddenly knocked back. But as the return times become longer and longer for these extreme cold events, it enables tropical species to get more and more of a foothold, and even maybe for populations to adapt in situ to allow them to tolerate more cold extremes in the future.”
The study, conducted by a team of 16 scientists led by the U.S. Geological Survey (USGS), focused on the effects warming winters will have on the movement of a broad range of cold-sensitive tropical plants and animals into the Southern U.S., especially into the eight subtropical U.S. mainland states: Florida, Alabama, Mississippi, Louisiana, Texas, New Mexico, Arizona and California. Williams and Katie Marshall of the University of British Columbia in Vancouver co-wrote the section on insects for the study.
The team found that a number of tropical species, including insects, fish, reptiles, amphibians, mammals, grasses, shrubs and trees, are enlarging their ranges to the north. Among them are species native to the U.S., such as mangroves, which are tropical salt-tolerant trees; and snook, a warm water coastal sport fish; and invasive species such as Burmese pythons, Cuban tree frogs, Brazilian pepper trees and buffelgrass.
“We don’t expect it to be a continuous process,” said USGS research ecologist Michael Osland, the study’s lead author. “There’s going to be northward expansion, then contraction with extreme cold events, like the one that just occurred in Texas, and then movement again. But by the end of this century, we are expecting tropicalization to occur.”
The authors document several decades’ worth of changes in the frequency and intensity of extreme cold snaps in San Francisco, Tucson, New Orleans and Tampa – all cities with temperature records stretching back to at least 1948. In each city, they found, mean winter temperatures have risen over time, winter’s coldest temperatures have gotten warmer, and there are fewer days each winter when the mercury falls below freezing.
Temperature records from San Francisco International Airport, for example, show that before 1980, each winter would typically see several sub-freezing days. For the past 20 years, there has been only one day with sub-freezing temperatures.
Changes already underway or anticipated in the home ranges of 22 plant and animal species from California to Florida include:
- Continuing displacement of temperate salt marsh plants by cold-sensitive mangrove forests along the Gulf and southern Atlantic coasts. While this encroachment has been happening over the last 30 years, with sea-level rise, mangroves may also move inland, displacing temperate and freshwater forests.
- Buffelgrass and other annual grasses moving into Southwestern deserts, fueling wildfire in native plant communities that have not evolved in conjunction with frequent fire.
- The likelihood that tropical mosquitos that can transmit encephalitis, West Nile virus and other diseases will further expand their ranges, putting millions of people and wildlife species at risk of these diseases.
- Probable northward movement, with warming winters, of the southern pine beetle, a pest that can damage commercially valuable pine forests in the Southeast.
- Recreational and commercial fisheries’ disruption by changing migration patterns and the northward movement of coastal fishes.
The changes are expected to result in some temperate zone plant and animal communities found today across the southern U.S. being replaced by tropical communities.
“Unfortunately, the general story is that the species that are going to do really well are the more generalist species — their host plants or food sources are quite varied or widely distributed, and they have relatively wide thermal tolerance, so they can tolerate a wide range of conditions,” Williams said. “And, by definition, these tend to be the pest species — that is why they are pests: They are adaptable, widespread and relatively unbothered by changes in conditions, whereas, the more specialized or boutique species are tending to decline as they get displaced from their relatively narrow niche.”
She cautioned that insect populations overall are falling worldwide.
“We are seeing an alarming decrease in total numbers in natural areas, managed areas, national parks, tropical rain forests — globally,” she said. ” So, although we are seeing some widespread pest species increasing, the overall pattern is that insects are declining extremely rapidly.”
The authors suggest in-depth laboratory studies to learn how tropical species can adapt to extreme conditions and modeling to show how lengthening intervals between cold snaps will affect plant and animal communities.
“On a hopeful note, it is not that we are heading for extinction of absolutely everything, but we need to prepare for widespread shifts in the distribution of biodiversity as climate, including winter climate, changes,” Williams said. “The actions that we take over the next 20 years are going to be critical in determining our trajectory. In addition to obvious shifts, like reducing our carbon footprint, we need to protect and restore habitat for insects. Individuals can create habitat in their own backyards for insects by cultivating native plants that support pollinators and other native insects. Those are little things that people can do and that can be important in providing corridors for species to move through our very fragmented habitats.”
USC Stem Cell study identifies molecular ‘switch’ that turns precursors into kidney cells
Kidney development is a balancing act between the self-renewal of stem and progenitor cells to maintain and expand their numbers, and the differentiation of these cells into more specialized cell types. In a new study in the journal eLife from Andy McMahon’s laboratory in the Department of Stem Cell Biology and Regenerative Medicine at the Keck School of Medicine of USC, former graduate student Alex Quiyu Guo and a team of scientists demonstrate the importance of a molecule called β-catenin in striking this balance.
β-catenin is a key driver at the end of a complex signaling cascade known as the Wnt pathway. Wnt signaling plays critical roles in the embryonic development of multiple organs including the kidneys. By partnering with other Wnt pathway molecules, β-catenin controls the activity of hundreds to thousands of genes within the cell.
The new study builds on the McMahon Lab’s previous discovery that Wnt/β-catenin can initiate progenitor cells to execute a lengthy and highly orchestrated program of forming structures in the kidney called nephrons. A healthy human kidney contains a million nephrons that balance body fluids and remove soluble waste products. Too few nephrons results in kidney disease.
Previous studies from the UT Southwestern Medical Center laboratory of Thomas Carroll, a former postdoctoral trainee in the McMahon Lab, suggested that Wnt/β-catenin signaling plays opposing roles in ensuring the proper number of nephrons: promoting progenitor maintenance and self-renewal, and stimulating progenitor cell differentiation.
“It sounded like Wnt/β-catenin is doing two things–both maintenance and differentiation–that seem to be opposite operations,” said Guo. “Therefore, the hypothesis was that different levels of Wnt/β-catenin can dictate different fates of the nephron progenitors: when it’s low, it works on maintenance; when it’s high, it directs differentiation.”
In 2015, it became more possible to test this hypothesis when Leif Oxburgh, a scientist at the Rogosin Institute in New York and a co-author of the eLife study, developed a system for growing large numbers of nephron progenitor cells, or NPCs, in a Petri dish.
Relying on this game-changing new system, Guo and his collaborators grew NPCs, added different levels of a chemical that activates β-catenin, and saw their hypothesis play out in the Petri dishes.
They observed that high levels of β-catenin triggered a “switch” in part of the Wnt pathway that relies on another family of transcription factors known as TCF/LEF. There are two types of TCF/LEF transcription factors: one type inhibits genes related to differentiation, and the other activates these genes. In response to high levels of β-catenin, the “activating” members of TCF/LEF switched places with the “inhibiting” members, effectively taking charge. This “switch” triggered NPCs to differentiate into more specialized types of kidney cells.
When they looked at low levels of β-catenin, they saw NPCs self-renewing and maintaining their populations, as expected. However, they were surprised to learn that β-catenin was not engaged with any of the known genes related to self-renewal and maintenance.
“β-catenin does something,” said Guo. “That is for sure. But how it does it is kind of mysterious right now.”
After publishing these results in eLife, Guo earned his PhD from USC, and began his postdoctoral training at UCLA. Helena Bugacov, a current PhD student in the McMahon Lab and a co-author of the eLife study, is now taking the lead in continuing the project–which has implications far beyond the kidney field, due to the broad role of Wnt throughout the body.
“Understanding how Wnt regulates these two very distinct cell outcomes of self-renewal and differentiation, which is very important for kidney development, is also important for understanding the development of other organs and adult stem cells, as Wnt signaling plays important roles in almost all developmental systems,” said Bugacov. “There is also a lot of attention from cancer researchers, as this process can go awry in cancer. Many therapeutics are trying to target this process.”
She added, “The more we know about things, the better we can inform work on developing human kidney organoid cultures, which can be more readily used to understand problems in human health, regeneration and development.”
Additional co-authors of the eLife study include: Albert Kim, Andrew Ransick, Xi Chen, and Nils Lindstrom from USC; Aaron Brown from the Maine Medical Center Research Institute; and Bin Li and Bing Ren from the University of California, San Diego. The research was supported by federal funding from the National Institute of Diabetes and Digestive and Kidney Diseases (grant number R01 DK054364).
Evidence of Antarctic glacier’s tipping point confirmed for first time
Researchers have confirmed for the first time that Pine Island Glacier in West Antarctica could cross tipping points, leading to a rapid and irreversible retreat which would have significant consequences for global sea level
Researchers have confirmed for the first time that Pine Island Glacier in West Antarctica could cross tipping points, leading to a rapid and irreversible retreat which would have significant consequences for global sea level.
Pine Island Glacier is a region of fast-flowing ice draining an area of West Antarctica approximately two thirds the size of the UK. The glacier is a particular cause for concern as it is losing more ice than any other glacier in Antarctica.
Currently, Pine Island Glacier together with its neighbouring Thwaites glacier are responsible for about 10% of the ongoing increase in global sea level.
Scientists have argued for some time that this region of Antarctica could reach a tipping point and undergo an irreversible retreat from which it could not recover. Such a retreat, once started, could lead to the collapse of the entire West Antarctic Ice Sheet, which contains enough ice to raise global sea level by over three metres.
While the general possibility of such a tipping point within ice sheets has been raised before, showing that Pine Island Glacier has the potential to enter unstable retreat is a very different question.
Now, researchers from Northumbria University have shown, for the first time, that this is indeed the case.
Their findings are published in leading journal, The Cryosphere.
Using a state-of-the-art ice flow model developed by Northumbria’s glaciology research group, the team have developed methods that allow tipping points within ice sheets to be identified.
For Pine Island Glacier, their study shows that the glacier has at least three distinct tipping points. The third and final event, triggered by ocean temperatures increasing by 1.2C, leads to an irreversible retreat of the entire glacier.
The researchers say that long-term warming and shoaling trends in Circumpolar Deep Water, in combination with changing wind patterns in the Amundsen Sea, could expose Pine Island Glacier’s ice shelf to warmer waters for longer periods of time, making temperature changes of this magnitude increasingly likely.
The lead author of the study, Dr Sebastian Rosier, is a Vice-Chancellor’s Research Fellow in Northumbria’s Department of Geography and Environmental Sciences. He specialises in the modelling processes controlling ice flow in Antarctica with the goal of understanding how the continent will contribute to future sea level rise.
Dr Rosier is a member of the University’s glaciology research group, led by Professor Hilmar Gudmundsson, which is currently working on a major £4million study to investigate if climate change will drive the Antarctic Ice Sheet towards a tipping point.
Dr Rosier explained: “The potential for this region to cross a tipping point has been raised in the past, but our study is the first to confirm that Pine Island Glacier does indeed cross these critical thresholds.
“Many different computer simulations around the world are attempting to quantify how a changing climate could affect the West Antarctic Ice Sheet but identifying whether a period of retreat in these models is a tipping point is challenging.
“However, it is a crucial question and the methodology we use in this new study makes it much easier to identify potential future tipping points.”
Hilmar Gudmundsson, Professor of Glaciology and Extreme Environments worked with Dr Rosier on the study. He added: “The possibility of Pine Island Glacier entering an unstable retreat has been raised before but this is the first time that this possibility is rigorously established and quantified.
“This is a major forward step in our understanding of the dynamics of this area and I’m thrilled that we have now been able to finally provide firm answers to this important question.
“But the findings of this study also concern me. Should the glacier enter unstable irreversible retreat, the impact on sea level could be measured in metres, and as this study shows, once the retreat starts it might be impossible to halt it.”
The paper, The tipping points and early warning indicators for Pine island Glacier, West Antarctica, is now available to view in The Cryosphere.
Northumbria is fast becoming the UK’s leading university for research into Antarctic and extreme environments.
As well as the £4m tipping points study, known as TiPPACCs, Northumbria is also the only UK university to play a part in two projects in the £20m International Thwaites Glacier Collaboration – the largest joint project undertaken by the UK and USA in Antarctica for more than 70 years – where Northumbria is leading the PROPHET and GHC projects. This particular study was funded through both TiPPACCs and PROPHET.
Diversity can prevent failures in large power grids
Integrated power grids offer benefits, but also pose challenges best addressed by leveraging differences
The recent power outages in Texas brought attention to its power grid being separated from the rest of the country. While it is not immediately clear whether integration with other parts of the national grid would have completely eliminated the need for rolling outages, the state’s inability to import significant amounts of electricity was decisive in the blackout.
A larger power grid has perks, but also has perils that researchers at Northwestern University are hoping to address to expedite integration and improvements to the system.
An obvious challenge in larger grids is that failures can propagate further — in the case of Texas, across state lines. Another is that all power generators need to be kept synchronized to a common frequency in order to transmit energy. The U.S. is served by three “separate” grids: The Eastern interconnection, the Western interconnection and the Texas interconnection, interlinked only by direct-current power lines. Any persistent deviation in frequencies within a region can lead to an outage.
As a result, researchers are searching for ways to stabilize the grid by looking for methods to mitigate deviations in the power generators’ frequencies.
The new Northwestern research shows that counter to assumptions held by some, there are stability benefits to heterogeneity in the power grid. Examining several power grids across the U.S. and Europe, a team led by Northwestern physicist Adilson Motter recently reported that generators operating on different frequencies return to their normal state more quickly when they are damped by “breakers” at different rates than generators around them.
The paper was published March 5 in the journal Nature Communications.
Motter is the Charles E. and Emma H. Morrison Professor in the department of physics and astronomy in the Weinberg College of Arts and Sciences. His research focuses on nonlinear phenomena in complex systems and networks.
Motter compares power grids to a choir: “It’s a little bit like a choir without a conductor. The generators have to listen to others and speak in sync. They react and respond to each other’s frequencies.”
Listen to an out-of-whack frequency, and the result can be a failure. Given the interconnected makeup of the system, a failure can propagate across the network. Historically, these malfunctions have been prevented by using active controllers. However, failures are often caused precisely by control and equipment errors. This points to a need to build additional stability within the design of the system. To achieve that, the team looked into leveraging the natural heterogeneities of the grid.
When the frequencies of the power generators are moved away from the synchronous state, they can swing around for a long time and even become more erratic. To mitigate these fluctuations, they came up with something akin to a door mechanism used to close a door the fastest, but without slamming.
“Mathematically, the problem of damping frequency deviations in a power generator is analogous to the problem of optimally damping a door to get it to close the fastest, which has a known solution in the case of a single door,” Motter said. “But it’s not a single door in this analogy. It’s a network of many doors that are coupled with each other, if you can imagine the doors as power generators.”
When creating an “optimal damping” effect, they discovered that rather than making each damper identical, damping the power generators in a way that is suitably different from each other can further optimize their ability to synchronize to the same frequency as quickly as possible. That is, suitably heterogenous damping across the network can lead to improved stability in the power grids studied by the team.
This discovery could have implications for future grid design as developers work to optimize technology and in considerations to further integrate now separated networks.
The paper is titled “Asymmetry underlies stability in power grids.” Additional co-authors include former postdoctoral researcher Ferenc Molnar and research professor Takashi Nishikawa.
The study was supported by Northwestern University’s Finite Earth Initiative (supported by Leslie and Mac McQuown) and ARPA-E Award No. DE-AR0000702 and also benefited from logistical support from the Northwestern Institute for Sustainability and Energy.
How Fortnite and Zelda can up your surgical game (no joke!)
Scalpel? Check. Gaming console? Check. Study finds video games can be a new tool on surgical tray for medical students
Video games offer students obvious respite from the stresses of studies and, now, a study from a University of Ottawa medical student has found they could benefit surgical skills training.
Arnav Gupta carries a heavy course load as a third-year student in the Faculty of Medicine, so winding down with a game of Legend of Zelda always provides relief from the rigorous of study. But Zelda may be helping improve his surgical education, too, as Gupta and a team of researchers from the University of Toronto found in a paper they recently published in the medical journal Surgery.
“Given the limited availability of simulators and the high accessibility of video games, medical students interested in surgical specialties should know that video games may be a valuable adjunct training for enhancing their medical education, especially in surgical specialties where it can be critical,” says Gupta, whose findings were deciphered from a systematic review of 16 studies involving 575 participants.
“Particularly, in robotic surgery, being a video gamer was associated with improvements in time to completion, economy of motion, and overall performance. In laparoscopic surgery, video games-based training was associated with improvement in duration on certain tasks, economy of motion, accuracy, and overall performance,” explains Gupta, who has been a gamer since age 8.
This study builds on past reviews and is the first to focus on a specific medical student population where this style of training could be feasibly implemented. Their timely study found some of the most beneficial games for students of robotic surgery and laparoscopy were: Super Monkey Ball, Half Life, Rocket League and Underground. Underground is purposely designed to assist medical students with their robotic surgery training via a video game console.
“While video games can never replace the value of first-hand experience, they do have merit as an adjunctive tool, especially when attempting to replicate important movements to surgery. For example, first-person shooting games require you to translate three dimensional motions onto a two-dimensional screen, which is like the concept of laparoscopic surgery,” says Gupta, whose studies are focused on surgery in ophthalmology, which makes games like Resident Evil 4 or Trauma Center: New Blood fitted for his own ambitions.
“I’m not joking when I say that games such as Fortnite have the potential to enhance those necessary movements, providing stronger motivational components and in a low stakes environment.”
Reports suggest 55 percent of university students are gamers and enjoy proficiency with video consoles. Yet, many medical students don’t admit to owning and using a gaming console.
“I think there definitely is some ambivalence towards video games in medicine,” says Gupta, who is also a fan of Witcher 3. “Given how accessible games have become and how video game technology is advancing, video games definitely are an easy go-to for the students who do love them in some capacity. The hope is that maybe this study can inspire someone to take advantage of video games’ unique capabilities, reduce the general ambivalence towards it, and develop some fun ways to let students engage with surgical education.”
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