When millions of people died in Europe during the Black Death, biodiversity suffered too, new research suggests. The findings suggest that human activities once promoted biodiversity in the landscape — and experts say we could use these findings to boost biodiversity in our modern agricultural landscapes.

The 14th century was a tumultuous time for the people of Europe. Persistent cold, wet weather at the beginning of the century led to widespread agricultural failures and unprecedented levels of starvation in what became known as the Great Famine from 1315 to 1317.

This was followed by the Black Death, an epidemic of bubonic plague caused by the bacterium Yersinia pestis that killed more than a third of Europe's population. As a result of the widespread deaths and resultant social upheaval, large swaths of agricultural land were abandoned. Population levels didn't begin to recover until the 16th century.

The Black Death era is the perfect opportunity to look at the effects of humans on biodiversity over a longer period, Jonathan Gordon, a paleoecologist at the Leverhulme Centre for Anthropocene Biodiversity at the University of York and first author of the paper, told Live Science.

In the study, which was published March 4 in the journal Ecology Letters, the researchers compared more than 100 European pollen records that included about 4,600 samples. The records came from sites ranging from the lowlands of France and uplands of the southwest United Kingdom to the Swiss Alps.

The pollen records "give us information on the past diversity of the plant records," Gordon said.

For example, cereal grains ‪—‬ such as wheat, barley and rye ‪—‬ were a fundamental part of medieval agriculture. The representation of pollen from these types of crops in the pollen record points to historic land use.

The researchers divided the pollen data into three categories based on the presence of cereal pollen: places where agricultural production went up, places where it went down, and places where there was no evidence of cereal cultivation.

"We found a decline in biodiversity overall, but the decline overall was driven by those landscapes that declined in agricultural production," Gordon said.

"In those landscapes where agricultural production went down, there was a reduction in biodiversity of around 40%. Then, after about 150 years, as populations started recovering and landscape disturbances started increasing again, biodiversity went up to slightly above the level it was before."

Mosaic landscapes

Many people think there was a "stable and pristine world in which the entry of people has only one result: net loss of species and homogenization," Erle Ellis, an agroecologist at the University of Maryland, Baltimore County who was not involved in the research, told Live Science in an email. "The paleoecologists have always known the story is far more complicated."

There is a growing body of evidence showing that people's long-term cultural shaping of their landscapes often creates more diverse habitats, known as "mosaics," that can sustain more species than simple homogenous landscapes can, he said.

Whereas modern agriculture focuses on single crops on plots of land, in previous centuries, "you had all these different types of agriculture operating within the same landscape," Gordon said.

"In that landscape, you had lots of natural features that remained from the Middle or Early Holocene (which began after the last Ice Age about 12,000 years ago)," he added. "You had old bits of woodland, you had heaths, you had ponds, and bits of secondary forest. It was all interlaced with these agricultural mosaics, and that led to raised biodiversity because there were more habitats for different plant species to exploit."

The findings highlight the differences between medieval and modern land use practices — and their consequences for biodiversity. Research suggests that during the 20th century, global biodiversity declined by up to as much as 11% and human activities‬, such as land-use changes, pollution, and climate change‬, are the major culprits. In agriculture, the practice of monoculture — where a single crop species is grown over a large area — reduces biodiversity.

"What this work contributes to showing is that, until relatively recently, even in Europe, very different forms of land management and interaction were practiced than exist today," Patrick Roberts, director of Department of Coevolution of Land Use and Urbanisation at the Max Planck Institute of Geoanthropology, told Live Science in an email.

"Rather than the monoculture, plantations, or uniform changes to landscapes we see in the 20th and 21st centuries, emphasis was placed on maintaining 'mosaics,'" said Roberts, who was not involved in the new research.

In the study, "we can see how relationships between people and biodiversity have changed through time and how people can actively use landscapes while maintaining biodiversity and mixed ecosystem functions," he said.

There is still more to understand about how humans' disappearance from landscapes in the Black Death era affected the natural world, Gordon said. "There are a lot of other types of diversity ‪—‬ not just the number of types, but what the different types present actually do." There may be a hundred types of plants in a landscape, but if they do the same thing, "you have low functional diversity," he said.

Functional diversity "is super important for how ecosystems adapt to changes in climate and how resilient they are, which is something we need for future-proofing our agricultural system," Gordon said.

When temperatures spike, California redwoods slow down photosynthesis, new research has found. This finding has serious implications for the long-term survival of the iconic trees in a warming world, and their role in storing carbon from the atmosphere.

California redwood (Sequoia sempervirens) forests are among the largest aboveground carbon stores on the planet. These towering trees are native to central and northern California, and evolved to take advantage of the region's historically mild weather. In recent decades, their range has contracted significantly. But climate change is threatening the health and function of these forests.

The region has seen significant warming in recent decades, and faces more frequent extreme heat days, with temperatures spiking above 100 degrees Fahrenheit (37 degrees Celsius). Now, in a new study, published Sept. 22 in the journal JGR Biogeosciences, a team of researchers has shown that California's renowned redwoods are struggling to photosynthesize in the heat.

Photosynthesis is the process used by plants, algae and some bacteria to turn sunlight into energy. It chemically converts carbon dioxide and water into sugars and oxygen.

"These trees adapted to grow in really temperate environments, so no one had really looked at the impact of heat on photosynthesis," study first author Lily Klinek, a doctoral candidate in the Plant Optics Lab at the University of California, Davis, told Live Science.

From 2022 to 2024, Klinek and colleagues measured how the leaves of redwoods in Garcia River Forest in Mendocino County responded to the heat. Once or twice a month, the researchers took three different California redwood leaf samples and measured their fluorescence and temperature.

A plant's molecules can use absorbed light in three ways: for photosynthesis, dissipated as heat, or reflected as light (florescence). Fluorescence is a proxy measurement to understand photosynthesis in the plant, Klinek said.

The researchers wrapped a fourth leaf in tinfoil for 20 minutes to put it in a state of "rest" before taking the same measurements. "When they're in a state of rest, we expose them to a pulse of light that’s in the wavelength they would use for photosynthesis to see what would be their maximum photosynthetic rate," Klinek said.

They found that on hot days, the leaves exposed to sunlight were up to 18 degrees Fahrenheit (10 degrees Celsius) hotter than the air temperature. "That's a huge difference and indicates that the leaves are stressed to the point where they can't thermoregulate effectively," Klinek said.

Many plants' leaves manage their temperature and photosynthesis by opening or closing their stomata, which are tiny pores on their surface. These stomata (from the Greek word for mouth) regulate the amount of carbon dioxide entering the plant, and how much oxygen and water vapor it releases. Lower carbon dioxide intake leads to reduced photosynthesis, meaning the plant has less energy.

The large differences between air and redwood leaf temperatures suggest that the leaves had closed their stomata to avoid losing water from evaporation during hot conditions and consequently overheated, Klinek said.

To further investigate the impact of heat on leaf physiology, the researchers took California redwood leaf samples back to the laboratory and exposed them to a range of temperatures while they were in water. Despite their access to water, the leaves still photosynthesized less as they got hotter, even though their stomata were open, Klinek said.

This shows that heat imposes direct limitations on redwood photosynthetical capacity, rather than indirectly decreasing that capacity by causing stomatal closure, the researchers wrote. The finding indicates that redwoods' ability to photosynthesise and store carbon will decrease as temperatures rise.

​​"It is not only stomatal closure that is causing reduced photosynthesis," Lucy Rowland, an ecologist at the University of Exeter in the U.K. who was not involved in the study, told Live Science in an email. "These trees are already suffering from the direct effects of heat on their photosynthetic systems."

The finding has serious implications for the future of redwoods and similar plants. "The points at which this damage becomes irreversible remains really poorly understood, but is something which is really essential to understand if we want to predict how our future climate is going to impact plants," she said.

The next step in Klinek's research is to move beyond leaf physiology to understand these thresholds on the trees and their ecosystems as a whole.

"We're not sure to what extent the effect that we saw is a reversible stress response and if they are sustaining damage from this constant stress," she said. Researchers need more data to "really get a better sense, beyond the leaf scale, how these ecosystems are responding to heat and drought," she added.

Researchers have observed the strongest candidate yet for a "microblazar" — a dazzling object that has long been predicted to exist but never spotted.

Observations of microblazars would give astronomers closer views of black holes emitting powerful jets of energy and help them understand how these extreme objects behave.

Blazars are some of the most energetic objects in the universe. They are a type of quasar — a brightly glowing object fueled by a supermassive black hole stripping material from its host galaxy and then ejecting some of it in powerful, opposing jets of particles and radiation. To qualify as a blazar, one of those near-light-speed jets needs to point directly at Earth. Astronomers have previously discovered smaller versions of quasars, dubbed microquasars, and long theorized that there must be smaller versions of blazars as well.

Now, an international team led by astronomers in Spain, the Netherlands and Argentina has described a microblazar in a study accepted for publication in the journal Astronomy and Astrophysics.

"It is the first time that we have a serious candidate," Josep Martí, an astronomer at the University of Jaén in Spain and first author of the study, told Live Science.

The object, called IRAS 18293-0941, is located in our galaxy, about 12,000 light-years from Earth, and it's hidden behind a veil of dust. It is a binary system that includes a black hole that orbits a hot, gigantic star every 11 days. Matter from the star falls into the black hole, and some of this material is jettisoned into the surrounding environment in two opposing jets. One of those jets flares toward Earth.

These objects, as well as microquasars in general, are tricky to observe, Martí said. "Because of stellar evolution, you need to catch the system at the right time," he added. "The microquasar phase of evolution is very short, and so it is difficult to find one in that phase."

Theorists predicted that microblazars would have special characteristics that should help define them. These features include powerful emissions across the electromagnetic spectrum, rapid changes in brightness (variability), and a hotspot behind them where its opposing jet heats up the interstellar medium in the opposite direction of Earth.

To observe IRAS 18293-0941, the study authors used a variety of instruments ‪—‬ including the Calar Alto Astronomical Observatory in Spain, a network of radio astronomy telescopes called the European VLBI Network, and the MeerKAT radio telescope array in South Africa ‪—‬ as well as archival data from the Very Large Array in New Mexico.

They found that IRAS 18293-0941 has all of the expected microblazar characteristics, except one ‪—‬ variability. Microblazars have rapid variability, which means their brightness changes a lot in a short period, because one of the jets is facing Earth and small changes in brightness are amplified by an effect called Doppler boosting.

Martí said IRAS 18293−0941's lack of rapid variability could be explained by the dense cloud of gas surrounding it, which could smooth out quick fluctuations in brightness.

The researchers are currently investigating whether the observed area behind the microblazar is in fact a hotspot, study co-author Pedro Luque-Escamilla, an astronomer at the University of Jaén, told Live Science.

Even with one of the expected features missing, this object is a promising candidate for the first known microblazar. "The claims and the results of the paper are sensible and there are no questionable hidden assumptions," Kinwah Wu, a theoretical astrophysicist at University College London who was not involved in the research, told Live Science in an email. "The source in this paper had shown signatures of interactions between the jets and the ambient material, which naturally leads to [particle] interaction."

Svetlana Jorstad, a senior research scientist at the Institute for Astrophysical Research at Boston University who was not involved in the research, told Live Science in an email that the new study was "very interesting, important and comprehensive."

Itumeleng Monageng, an astronomer at the University of Cape Town who was also not involved in the research, added that the team's observations "presents a previously overlooked mechanism for generating some of the highest energy emissions observed."

Microblazars "may power some of the universe's most energetic processes," Monageng told Live Science in an email.

Martí, J., Luque-Escamilla, P. L., Marcote, B., Abaroa, L., Aguasca-Cabot, A., Combi, J. A., Romero, G. E., Paredes, J. M., García, F., Fogantini, F., Saavedra, E. A., Del Ser, D., & Van Den Eijnden, J. (2026). A Galactic microblazar as a potential accelerator of ultra-high-energy particles. Astronomy and Astrophysics. https://doi.org/10.1051/0004-6361/202661105

See how much you know about black holes with our black hole quiz!

In the event of a global catastrophe, such as a nuclear war, an enormous volcanic eruption or large asteroid strike, the best place to be is Australia, according to a new study.

Researchers looked at the places that were most resilient to global catastrophic risks, which are events that would kill more than 10% of the global population over several months or years.

"These kinds of catastrophes are under-researched" because they are not very likely, study first author Florian Ulrich Jehn, a researcher at FernUniversität in Hagen, Germany, told Live Science. "That makes them easy to ignore."

But they are still possible — and no country would be unaffected if they occurred, he said. And some places are more vulnerable than others.

In the new study, published Aug. 23 in the journal Global Challenges, researchers analyzed studies across a variety of disciplines such as food security, biological weapons, and volcanism, to identify potential global catastrophic risks and the factors that helped communities to endure them in the past or on a smaller scale. They also brought in subject experts to add discipline-specific papers to their database.

The team identified three broad types of risk: events that would block out sunlight, such as nuclear war or a huge volcano explosion); events that destroy global infrastructure, such as a geomagnetic storm or massive cyber attack; and biological hazards, such as natural or human-caused infectious diseases that would kill much of the population.

These events, the authors wrote, would have significant and long-lasting global consequences. Many would result in global famine from crops failing and trade networks falling apart. "The food system is often the thing that gets you," Jehn said.

A trade-off of risks

The team identified characteristics that made countries more resilient to catastrophe and better able to feed their inhabitants. And while "no single place on Earth" would be resilient against all catastrophic risks, the authors wrote, some would fare better than others.

The team found that wealthier countries and regions with a strong industrial base that are not highly reliant on global trade are better able to weather global disasters.

With a strong industrial base, countries are able to manufacture goods that they cannot import, making them more resilient.

Geography also plays a role. Large islands have an advantage over continents because they can easily isolate, but they also need to have an economy that can at least partially support itself, the researchers said. If an island is highly reliant on international trade, like Japan, it will struggle if global trade networks are disrupted, the study found.

Certain countries and regions are less resilient in the face of some types of catastrophes, even if they are wealthy. For example, countries with nuclear capabilities, such as the U.S., the U.K., France, Israel, Russia, Pakistan, and India, are more at risk of being involved in nuclear war. This makes the Northern Hemisphere, where NATO countries are situated, more vulnerable to nuclear attack than places in the Southern Hemisphere.

There are also fewer volcanoes in the southern half of the globe, while the Southern Hemisphere has more ocean to act as a climate buffer, making countries there more resilient to a huge volcanic eruption, the study found.

Global resilience

There are some factors that make all countries better able to endure disasters in general, such as democratic processes and equality, Jehn said.

"When these catastrophes happen, you have to make the right decisions, and this depends on whether your country has functional governance," Jehn said. "Inequality makes governance worse, because it leads to things like elite rivalries, or less state capacity."

Australia came out as the best location to weather a catastrophic event that decimated global populations. It is in the Southern Hemisphere, so far away from the most likely location of a nuclear conflict (although the authors warn that it is allied with the U.S., which might increase its risk exposure). It is a major food producer, with diverse climatic zones, and has significant energy infrastructure.

Next best spots are Argentina, Brazil and New Zealand. New Zealand ranks lower than Australia because it has active volcanoes, a small industrial base, and is surrounded by water and vulnerable to tsunamis. Meanwhile, Brazil and Argentina have high levels of inequality and historical political instability, the authors wrote.

They also note that Iceland was a contender for a safe refuge, but its location in the far north makes it vulnerable to temperature shocks if a major incident were to block out sunshine.

The U.S. is not particularly well-placed to weather a global catastrophe, the study found. The country is exposed to the threat of geomagnetic storms because of its location and to nuclear war. The authors also pointed to the country’s poor COVID-19 outcomes, which appeared to be due to "a lack of political will and poor social cohesion."

David Denkenberger, director at Alliance to Feed the Earth in Disasters (ALLFED) and a researcher at the University of Canterbury in New Zealand, told Live Science that the new study aids our understanding of future risks by considering a wider range of catastrophes.

"No country is resilient to every catastrophe, and this is an important central finding," he said. "A useful next step would be to quantify the relative likelihood and severity of different catastrophes, and the importance of different resilience factors, because these factors can involve significant trade-offs," said Denkenberger, who has previously collaborated with Jehn but is not an author on the paper.

How to be more resilient

Even though these global catastrophes are unlikely, it is important to include them on national risk registers and have international trade agreements in place in case they come to pass, Jehn said. "When global catastrophes happen, then you would likely have to restructure the food system — where it is produced, where it is traded," he said. "The chance to find a good compromise after the catastrophe has happened seems slim."

Denkenberger echoed his comments. The study, he said, "makes it clear that regional resilience to global catastrophic risk requires investment in practical preparedness, including food-system resilience, critical infrastructure, coordinated trade and governance."