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      A biogeochemist is tracking the movements of toxic mercury pollution

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      One of the world’s richest biodiversity hot spots is Peru’s Madre de Dios, a region of the Amazon nestled at the base of the Andes mountains. When biogeochemist Jacqueline Gerson first traveled there in 2017, she found herself on a boat headed downstream through the forest. As the riverbanks passed by, she observed a scenic shift.

      At first, “it was beautiful, primary old-growth forest, lots of birds, lots of different wildlife,” says Gerson, a Ph.D. student at Duke University at the time. “Then, as I continued downstream … first you see these rocks,” she adds. “As you keep going, you see pile after pile after pile, and then you started to see some deforestation.”

      She was witnessing the signs of artisanal and small-scale gold mining. Unlike large-scale industrial operations with fleets of dump trucks and excavators, workers here use basic tools or their own hands to extract ore. These informal gold-mining efforts are so prolific in Madre de Dios that they support at least half of the region’s economy.

      In Madre de Dios, artisanal and small-scale gold miners tear down lush tracts of Amazonian rainforest to make way for mining operations, leaving behind mounds of sediment and pits that fill with water.Melissa Marchese

      But there is a price to that gain. The small-scale miners mix mercury into riverbank sediments that contain flecks of gold. This produces a gold-mercury amalgam that can easily be separated from the muck and then burned to isolate the gold. But that burning also releases fumes of mercury into the open air.

      For Gerson, now at Cornell University, illuminating how toxic contaminants flow through the environment is a calling. She studies how human activities contribute to these contaminants and alter their paths. More

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      Climate change could double U.S. temperature-linked deaths by mid-century

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      Heat-related deaths in the United States are on the rise. But how bad will it be 20, 30 or 40 years from now? Scientists now have a clue.

      Currently, an estimated 8,000-plus deaths in the United States every year are associated with extreme temperatures, both hot and cold. Within the next few decades, that number could double or even triple, largely due to heat, researchers report September 20 in JAMA Network Open.

      “As the climate warms, the frequency, duration and intensity of heat waves is increasing. Understanding how this will impact our health is crucial,” Sameed Khatana, a cardiologist at the University of Pennsylvania, says. Our bodies are capable of bearing sweltering temperatures, but as temperatures rise, this ability is pushed to its limit (SN: 6/21/24). More

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      Earth’s ancient ‘greenhouse’ conditions were hotter than thought

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      Over the last 485 million years, Earth has been both a lot colder and a lot hotter than once thought.

      A new temperature timeline that combines geologic data with computational simulations reveals a rich, detailed and dramatic picture of the ebb and flow of icehouse and greenhouse conditions on Earth throughout this span of time, which includes most of the Phanerozoic Eon. The timeline shows Earth’s average temperature dropping to as low as 11° Celsius and rising to as high as 36° C, researchers report in the Sept. 20 Science. More

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      Can solar farms and crop farms coexist?

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      Transcript

      James McCall: Solar production in the US really started to pick up around 2012. As solar really became mainstream, there was a lot more concerns of land use changes.

      Ravi Sujith: If you look at the type of land that’s been converted for solar installations, over 60 percent of those landscapes are converted croplands.

      Chong Seok-Choi: They both require flat areas with a lot of sun, and that’s close to transmission infrastructures. So in this context, it is important for us to figure out how to combine farming and solar power production so that both can exist in harmony. More

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      Mega El Niños kicked off the world’s worst mass extinction

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      A barrage of intense, wild swings in climate conditions may have fueled the largest mass extinction in Earth’s history. A re-creation of how ancient sea surface temperatures, ocean and atmosphere circulation, and landmasses interacted revealed an Earth plagued by nearly decade-long stints of droughts, wildfires and flooding.

      Researchers knew that a spike in global temperatures — triggered by gas emissions from millions of years of enormous volcanic eruptions in what is now Siberia — was the likely culprit behind a mass extinction roughly 252 million years ago (SN: 8/28/15). But it was the resulting catastrophic “mega El Niños” that whiplashed ecosystems, ultimately wiping out some 90 percent of all ocean species and 75 percent of those on land, researchers report in the Sept. 13 Science. More

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      How much is climate change to blame for extreme weather?

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      This video was supported by funding from the Howard Hughes Medical Institute.

      TRANSCRIPT

      Maria Temming: In 2021, a historic heat wave baked the Pacific Northwest killing hundreds of people and fueling wildfires. Researchers later reported that human-caused climate change made this heat wave at least 150 times more likely.

      But how do scientists figure out how much climate change is to blame for a specific weather event?

      Researchers use a variety of techniques for this work, which is called extreme event attribution. One method compares the world we have today–which has warmed 1.2 degrees Celsius since the Industrial Revolution –with what the world would look like without climate change. Researchers estimate what that second world would look like based on historic trends in weather data and climate models. More

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      Fiddler crabs are migrating north to cooler waters

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      This video was supported by funding from the Howard Hughes Medical Institute.

      TRANSCRIPT

      David Johnson: So in 2014, we were on a muddy bank in the marsh up here in Massachusetts, and I saw this small crab scuttle across the mud bank and pop into a hole. And so I dug out the crab, and it was a fiddler crab. I was shocked. I had worked a decade in this marsh and had never seen a fiddler crab up here. More

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      Summer-like heat is scorching the Southern Hemisphere — in winter

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      It’s winter in the Southern Hemisphere — but you wouldn’t know it from the thermostat.

      On August 26, a remote stretch of the coastline in Western Australia experienced the highest winter temperature ever recorded anywhere in the country: a blistering 41.6° Celsius (107° Fahrenheit).

      In Bidyadanga, an Aboriginal community in Western Australia, the overnight low temperature on August 28 was a staggering 27.2° C (81° F). That’s in winter, when the long-term average nighttime temperature has been around 15° C (59° F). Such heightened nighttime temperatures can disrupt sleep, leading to decreased cardiovascular and mental health (SN: 8/6/23). More