In 2015, Sweden drew international attention when researchers reported that its Conservation Performance Payment (CPP) program, the oldest initiative of its kind, had helped boost populations of the endangered wolverine.

More than a decade later, however, that early success appears increasingly difficult to maintain. The program was designed to benefit both wolverines and the Indigenous Sámi reindeer herders who share the landscape with them. New findings suggest that the arrangement is under growing strain.

Researchers from the University of York and the Swedish Agricultural University found that documented wolverine numbers have dropped sharply in parts of northern Sweden where the species was once strongest. At the same time, government payments have remained unchanged for two decades, and many local communities say they no longer trust the system.

The findings, published in Conservation Letters, suggest that governments risk undermining conservation gains when they fail to address the long-term financial and social costs that wildlife recovery can place on local residents.

A Revolutionary Approach to Predator Conservation

Dr. Hanna Pettersson of the University of York’s Leverhulme Centre for Anthropocene Biodiversity explained how the program differed from traditional compensation systems.

“Implemented in 1996, the scheme was at the time revolutionary. Instead of paying reindeer herders for damages caused by predators, the government paid communities for coexisting with them, whether or not damage actually occurs.

“The idea is to tie an income to the presence of the predator, providing an incentive to find ways to live alongside them, thus decreasing conflicts and improving social justice.

“Initial findings showed encouraging results of the scheme, namely a marked increase of the wolverine population, but after studying 30 years of data from the scheme, we have shown that this success has not been sustained.”

To investigate the program’s long-term impact, Dr. Pettersson accompanied wildlife rangers working in the Arctic. The researchers also combined ecological monitoring records with interviews conducted in Norrbotten, Sweden’s northernmost county.

Their results point to growing challenges within the program and raise broader concerns for conservation efforts elsewhere.

Wolverine Numbers Decline in Northern Sweden

The study found that wolverines are spreading into southern parts of Sweden while declining in regions that historically supported the largest populations.

In the early 2000s, Norrbotten accounted for roughly two-thirds of all documented wolverine reproductions in Sweden. Today, that figure has fallen to less than one-third, and the county regularly fails to meet minimum conservation targets.

Researchers say stagnant funding has become a major issue.

Dr. Pettersson said: “The payments to the reindeer herders from the scheme have remained frozen at 200,000 SEK per predator reproduction since 2002, but due to rising costs and meat prices, the real value of the payment has approximately halved over the last two decades.

“While the Sámi Parliament calculates the legal payout should be at least 480,000 SEK to comply with the law, the government offered only a 25,000 SEK increase in 2024.”

Climate Change and Tracking Challenges

The research also identified climate change as an additional obstacle. Shifting snow conditions across the Arctic have made wolverine tracks harder to detect and document.

As a result, official counts may not fully reflect the true number of animals. Researchers noted that many apparent wolverine sightings were rejected because they did not satisfy strict documentation requirements.

According to Dr. Pettersson, these challenges illustrate the need for governments to adapt conservation programs as conditions change.

“If a government fails to adapt payments to rising costs of coexistence, the burden is shifted onto local, often marginalized, communities, who in this case are already straining under the cumulative impacts of mining, forestry, and climate change.

“It is a warning sign for other global conservation efforts. Governments must plan ahead and adapt interventions to changing conditions and local needs.”

A team from XPANCEO, working with scientists from the National University of Singapore and the University of Chemistry and Technology, Prague, has reported a major advance in that effort. Their study focuses on a layered crystal called molybdenum oxychloride (MoOCl₂), which displays a collection of unusual optical properties that could help dramatically shrink future optical devices.

Published in Nano Letters, the research presents the first experimental mapping of the crystal’s optical behavior. The findings show that MoOCl₂ exhibits the strongest light-bending effect ever measured in a natural material, potentially opening a path toward much smaller and more capable optical technologies.

A Crystal That Acts Like Metal and Glass

Researchers describe MoOCl₂ as a kind of optical “chameleon.” Its behavior changes depending on how the crystal is oriented.

When positioned one way, it reflects light much like a metal. Rotate it by 90 degrees, and it becomes transparent like glass. This unusual characteristic stems from its extreme optical anisotropy, meaning its properties vary dramatically depending on direction.

The crystal also has an in-plane birefringence value of approximately 2.2, allowing it to split and bend light with exceptional efficiency. For XPANCEO, this could make it possible to perform the sophisticated light control needed for AR displays using materials that are thousands of times thinner than a human hair.

Rare Light-Slowing Effect Found in Visible Light

The researchers also identified a rare epsilon-near-zero point at 512 nm (green light).

At this point, part of the material’s optical response falls almost to zero. As a result, light effectively slows down while the electric field inside the crystal becomes stronger. This combination can significantly enhance interactions between light and matter.

For integrated photonic chips, this effect could be especially valuable. Stronger light-matter interactions may enable faster data processing while using much less power.

Why Scientists Are Interested in MoOCl₂

Physicists have been studying MoOCl₂ for several years because of its unusual electronic structure.

The material is classified as a “bad metal” and contains one-dimensional chains of molybdenum atoms. These chains allow electrons to move more easily in one direction than another. As a result, the crystal behaves like a metal along one axis and like a dielectric material along the perpendicular axis, creating its exceptionally strong anisotropy.

Previous studies published in Science and Nature Communications had already observed tightly confined light waves called hyperbolic plasmon polaritons traveling through the crystal. Those experiments showed that MoOCl₂ could guide light in highly directional and unexpected ways.

However, an important piece of the puzzle was still missing. Scientists could observe the optical effects, but they had not directly measured the material’s full optical constants. Without those measurements, designing practical devices based on the crystal remained much more difficult.

Mapping the Crystal’s Optical Properties

The new work provides those missing measurements.

The researchers found that near 512 nanometers in the green region of the visible spectrum, one component of the crystal’s optical response approaches zero. In practical terms, this can intensify the electric field inside the material and slow light down, squeezing electromagnetic energy into a very small volume and boosting light-matter interactions.

This phenomenon is known as a visible-light epsilon-near-zero (ENZ) point. While many materials exhibit ENZ behavior only in the deep ultraviolet or mid-infrared regions, MoOCl₂ reaches this state within the visible spectrum. That is particularly important because many existing technologies, including lasers, microscopes, cameras, and sensing systems, already operate in this range.

“Observing a phenomenon is the first step, but engineering requires precise numbers,” said Dr. Valentyn Volkov, founder and CTO of XPANCEO and corresponding author of the study. “By rigorously measuring the complete dielectric tensor of MoOCl₂, our work provides the experimental foundation needed to understand why this material behaves the way it does and to design around it with greater confidence. That makes it a valuable scientific result for the field, with possible relevance across compact polarization optics, nonlinear devices, and, in the longer term, highly miniaturized integrated systems including smart contact lenses.”

Shrinking Future Optical Hardware

The detailed optical map also highlights the material’s potential for further miniaturization of optical technologies.

Because of its strong structural anisotropy, MoOCl₂ functions as a natural hyperbolic medium. In simple terms, this allows light to travel through the crystal in highly directional nanoscale paths without diffracting (or scattering), a key requirement for building smaller optical circuits.

Its ability to operate in the visible spectrum further strengthens its appeal for integrated photonic chips, where light must be routed, filtered, and concentrated within extremely small spaces.

The researchers point to several possible applications. These include ultrathin broadband polarizers that control the direction of light in compact optical systems, as well as sub-diffractional waveguides capable of guiding light through spaces smaller than those allowed by conventional optics.

The findings also suggest opportunities in nonlinear nanophotonics, where intense light-matter interactions can be used to create new colors of light or process optical signals more efficiently.

One approach that has drawn growing interest is intermittent energy restriction (IER), a form of dieting in which periods of reduced calorie intake are followed by periods of more typical eating. Research published in 2023 suggests that this strategy may do more than reduce body weight. It may also shift the relationship between gut bacteria and brain activity in ways that are closely tied to appetite and food behavior.

“Here we show that an IER diet changes the human brain-gut-microbiome axis. The observed changes in the gut microbiome and in the activity in addition-related brain regions during and after weight loss are highly dynamic and coupled over time,” said last author Dr. Qiang Zeng, a researcher at the Health Management Institute of the PLA General Hospital in Beijing.

Intermittent fasting and the brain

To explore what happens inside the body during weight loss, the researchers studied 25 adults with obesity in China. The volunteers, who were about 27 years old on average, had a BMI between 28 and 45.

The team used several tools to track changes over time. Stool samples were analyzed with metagenomics to measure the composition of the gut microbiome. Blood tests were used to monitor metabolic and physiological changes. The researchers also used functional magnetic resonance imaging (fMRI) to examine activity in brain regions involved in appetite, emotion, attention, learning, inhibition, and reward.

“A healthy, balanced gut microbiome is critical for energy homeostasis and maintaining normal weight. In contrast, an abnormal gut microbiome can change our eating behavior by affecting certain brain area involved in addiction,” explained coauthor Dr. Yongli Li from the Department of Health Management of Henan Provincial People’s Hospital in Henan, China.

A carefully controlled weight loss program

The study began with a 32 day high controlled fasting phase. During this period, participants received meals designed by a dietitian. Their calorie intake was gradually reduced in steps until it reached about one quarter of their basic energy needs.

This was followed by a 30 day low controlled fasting phase. During this stage, participants were given a list of recommended foods rather than fully prepared meals. Those who followed the plan exactly would consume 500 calories per day for women and 600 calories per day for men.

By the end of the intervention, participants had lost an average of 7.6 kilograms, equal to about 7.8% of their starting body weight. They also had reductions in body fat and waist circumference.

The metabolic improvements extended beyond weight. Blood pressure fell, as did fasting plasma glucose, total cholesterol, HDL, LDL, and the activity of key liver enzymes. According to the researchers, these changes suggest that intermittent energy restriction may help reduce obesity related problems such as hypertension, hyperlipidemia, and liver dysfunction.

Brain and gut changes moved together

The researchers found that the weight loss program was linked to lower activity in several brain regions involved in appetite and addiction related behavior. These changes may help explain why dieting affects not only body size, but also food cravings, self control, and the drive to eat.

At the same time, the gut microbiome shifted. The abundance of Faecalibacterium prausnitzii, Parabacteroides distasonis, and Bacterokles uniformis rose sharply. Escherichia coli decreased.

Further analysis suggested that certain microbes were connected with activity in specific brain areas. The abundance of E. coli, Coprococcus comes, and Eubacterium hallii was negatively associated with activity in the brain’s left orbital inferior frontal gyrus, a region involved in executive function and willpower during weight loss.

Other bacteria showed the opposite pattern. P. distasonis and Flavonifractor plautii were positively linked with brain regions involved in attention, motor inhibition, emotion, and learning.

These findings point to a striking possibility: as people lose weight, the gut microbiome and the brain may change together. The study cannot prove whether gut bacteria drive the brain changes, whether the brain drives microbial changes, or whether another factor influences both. Still, the results add to evidence that weight control is not just a matter of willpower or calories. It may involve a changing biological conversation between the gut and the brain.

A two way conversation inside the body

“The gut microbiome is thought to communicate with the brain in a complex, two-directional way. The microbiome produces neurotransmitters and neurotoxins which access the brain through nerves and the blood circulation. In return the brain controls eating behavior, while nutrients from our diet change the composition of the gut microbiome,” said coauthor Dr. Xiaoning Wang from the Institute of Geriatrics of the PLA General Hospital.

This two way communication may help explain why obesity is so difficult to treat. Hunger, cravings, mood, reward, and metabolism are all shaped by biological signals. The gut microbiome can produce compounds that influence inflammation, metabolism, and nervous system activity. The brain, in turn, helps regulate food choices and eating behavior.

The 2023 findings suggest that successful weight loss may involve changes across this entire system rather than in one isolated organ.

What later research adds

Research published after the 2023 study has continued to support the idea that fasting can influence the gut microbiome, although the evidence remains complex. A 2024 systematic review of human studies found that intermittent fasting appears to affect gut microbial richness, diversity, and composition. However, the authors also noted that results varied widely between studies, and more research is needed to determine which changes are truly beneficial for health.

Another 2024 clinical study compared intermittent fasting combined with protein pacing to continuous calorie restriction in adults with overweight or obesity. Both diets reduced calorie intake, but the fasting and protein pacing group showed greater weight loss and more pronounced shifts in the gut microbiome. The researchers reported increases in microbes and metabolic signals associated with improved body composition and fat loss.

Together, these later findings strengthen the broader picture: fasting based interventions may reshape the gut microbiome in meaningful ways. However, they also show that the details matter. The type of fasting, calorie intake, protein intake, fiber intake, meal timing, and individual biology may all influence the outcome.

The next question for weight loss research

The original 2023 study was small and correlational, so it cannot show cause and effect. It also focused on a specific group of participants and a short term intervention. Larger and longer studies will be needed to determine whether certain microbes or brain regions can reliably predict who will lose weight, who will keep it off, and which diets work best for different people.

Coauthor Dr. Liming Wang, likewise from the Health Management Institute in Beijing, said: “The next question to be answered is the precise mechanism by which the gut microbiome and the brain communicate in obese people, including during weight loss. What specific gut microbiome and brain regions are critical for successful weight loss and maintaining a healthy weight?”

For now, the research offers a more detailed view of what may happen during intermittent fasting. Weight loss may not be limited to shrinking fat stores. It may also involve a synchronized shift in gut bacteria, metabolism, and brain activity that changes how the body responds to food.