Some of the most famous sharks, like the white shark or the extinct megalodon, are unusual in being among the mere ~1% of shark species to be considered warm-blooded or “regional endotherms.”

It had always been thought warmer muscles help fish be powerful and athletic, with regional endothermy only seen in apex predators like the great white or giant tuna. But there has also been some debate about when regional endothermy evolved, and whether extinct species like the megalodon was warm bodied.

In a new study led by Trinity College Dublin, researchers have found that a relatively ancient (but still-living) shark species — the smalltooth sand tiger, thought to have diverged from the Meg at least 20 million years ago — has anatomic features suggesting it is a regional endotherm. Coming hot on the fins of a similar shock that slow-moving, filter-feeding basking sharks are also regional endotherms, the researchers now believe there are more warm-blooded sharks than science thought, and that warm bloodedness evolved quite a long time ago.

Dr Nicholas Payne from Trinity’s School of Natural Sciences was senior author of the study, published this week in Biology Letters. He said:

“We think this is an important finding, because if sand tiger sharks have regional endothermy then it’s likely there are several other sharks out there that are also warm-bodied.

“We used to think regional endothermy was confined to apex predators like the great white and extinct megalodon, but now we have evidence that deep water ‘bottom dwelling’ sand tigers, and plankton-eating basking sharks also are warm bodied. This raises plenty of new questions as to why regional endothermy evolved, but it might also have important conservation implications.”

The research team (including scientists from University of Pretoria, ZSL, University of Zurich, Swansea University, Smithsonian Tropical Research Institute and University College Dublin College of Agriculture Food Science and Veterinary Medicine) undertook dissections of dead smalltooth sand tiger sharks that washed up in Ireland and the UK in making their discoveries.

Dr Haley Dolton, also from Trinity, was lead author of the study. She said:

“Our understanding of science continually grows and it’s becoming clear that whenever regional endothermy evolved in the past it has been retained in a growing number of shark species with very different life styles. When we first realised that the smalltooth tigers have traits associated with regional endotherms I thought ‘here we go again!’, but the next time we see it in another species I might be a little less shocked.

“The discovery itself is very interesting for a marine biologist, but it also has major implications from a conservation perspective for regional endotherms. We believe changing environments in the deep past was a major contributor to the megalodon’s extinction, as we think it could no longer meet the energetic demands of being a large regional endotherm. We know the seas are warming at alarming rates again now and the smalltooth tiger that washed up in Ireland was the first one seen in these waters. That implies its range has shifted, potentially due to warming waters, so a few alarm bells are ringing.”

Clusters of landslides offer a potential record of earthquakes, if researchers can determine when the landslides occurred. The new study published in the Bulletin of the Seismological Society of America combines information about the location of these Puget Lowlands landslides along with new dates obtained from measuring the surface roughness of the landslides.

The combination of data helped Erich Herzig of the University of Washington and colleagues uncover strong evidence of the last known major Seattle Fault earthquake, thought to be a magnitude 7 to 7.5 event. (A recent study suggested that there may have even been a double earthquake at the time in the region.)

The researchers compared their new landslide map to ground motions generated by different Seattle Fault earthquake scenarios. The scenario that best matches the landslide clusters, they found, is one that produces the strongest shaking in a west to east band from west Seattle to Mercer Island and the bluffs bordering Puget Sound.

“While other studies have refined our understanding of the overall strength or timing of the 1,100-year-old Seattle Fault earthquake, to our knowledge, this is the first study that has attempted to characterize the locations of strong shaking,” Herzig said.

Herzig and colleagues also uncovered other landslide clusters at 4600-4200 years ago, 4000-3800 years ago, 2800 to 2600 years ago, and 2200 to 2000 years ago that could be signs of older Seattle Fault earthquakes.

They began by mapping more than 1,000 deep-seated landslides across the Puget Lowlands — deep-seated refers to landslides where the slide plane lays below the roots of the trees — using a technique called airborne lidar.

“Airborne lidar is a technology where a plane mounted with lasers is used to measure the shape of the land surface in detail, even through vegetation,” Herzig explained. “In the past few years this technology has been able to produce maps at one meter resolution or better, which is essential for measuring roughness as we do in the paper.”

Measuring the roughness of a landslide surface is a relatively new technique used by scientists to estimate the age of a landslide, he noted. The general idea is that ground surfaces roughen after the mass movement of rocks and soil, so that landslide deposits are the roughest right after the landslide occurs and become smoother over time. By modeling this age-roughness relationship, with information from landslides dated by other means such as carbon dating, researchers can estimate when a particular landslide took place.

For the landslides in the BSSA study, Herzig and colleagues calculated roughness by measuring variations in the land surface in a 15-meter-wide circle. Carbon dating of wood at some landslides provided data for calibrating the landslide ages.

The researchers uncovered spatial patterns in the landslides that correlate with the ground motions predicted by models of Seattle Fault earthquakes. They also noted that the timing of landslides in the Puget Lowland fits better with a model of a pulse of landslides at the time of the last major Seattle Fault earthquake, rather than a model of landslides happening steadily through time.

The researchers said their method offers a powerful new way of extracting information about past earthquakes from landslide data.

“This method is best suited to understanding landscapes that have hills that are steep enough to have landslides, and that have infrequent but powerful earthquakes,” Herzig said. “In the U.S., that could mean other locations in the Puget Lowlands area, or places in the New Madrid seismic zone. Other locations around the world could also be interesting to study, such as the Hinagu Fault zone in Japan, or the Hellenic arc in Greece.”

The research finds that 12 countries have the technical ability to sequester over 20% of their current total greenhouse gas emissions by converting crop residues to biochar. Bhutan leads the way with the potential to sequester 68% of its emissions in the form of biochar, followed by India, at 53%. The study, “Potential for Biochar Carbon Sequestration from Crop Residues: A Global Spatially Explicit Assessment,” published in the journal GCB Bioenergy.

“We are entering an unprecedented era in which even a rapid and profound reduction in fossil fuel use will not be enough to avoid severe harms to both humans and ecosystems from climate change,” said co-lead author Dominic Woolf, a senior research associate in the School of Integrative Plant Science at Cornell University.

“We also need to draw down excess CO₂,” he said. “Making biochar from crop residues is one of the few tools we have that can do this at scale without competing for land.”

Biochar improves soil fertility and benefits plant growth, while also offering a way to remove CO₂ from the atmosphere. When added to soils, biochar sequesters carbon in the soil for centuries.

The study finds that if the total amount of crop residues generated by agriculture globally were converted into biochar, it would sequester a maximum of one billion metric tons of carbon stored annually. Three-quarters of that carbon would remain sequestered after 100 years, which represents enough to offset about 80% of all greenhouse gas emissions from agriculture.

“Even when considering limitations on sustainable residue harvesting and competing usage for crop residues — such as livestock feed — the global biochar production potential is approximately half of that amount,” Woolf said.

When considering these limitations, potential global biochar production amounts to 510 million metric tons of carbon per year, with roughly 360 million metric tons remaining sequestered after 100 years.

“The high-resolution maps of crop residue production and biochar sequestration will provide valuable insights and support decision-making related to biochar production and investment in biochar production capacity,” Woolf said.

The study was funded by the Nature Conservancy and the Bezos Earth Fund.