Environment

An experiment to grow new forests in central Mexico offers hope that the crucial winter habitat for millions of migrating monarch butterflies could survive into the next century.

When scientists decided to plant hundreds of baby oyamel fir trees (Abies religiosa) about 100 kilometers from their native habitat, they weren’t sure how many trees would survive. Today, most of the saplings are flourishing, researchers report September 17 in Frontiers in Forests and Global Change. Even at an altitude of 3,800 meters, high above where the trees usually grow, almost 70 percent of the saplings survived at least three years. More

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

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

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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

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

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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

Access to clean water is a human right — one that half of the world may not have.

Out of the roughly 8 billion people on Earth, more than 4.4 billion lack access to safely managed drinking water, researchers report August 15 in Science. The estimate, based on computer simulations of data from low- and middle-income countries, is more than double the figure calculated by the World Health Organization (SN: 8/16/18).

“The number of people whose basic human right to safe drinking water is not being met may therefore be significantly underestimated,” says environmental microbiologist Esther Greenwood of Eawag, an aquatic research institute in Dübendorf, Switzerland. More

What’s dumped into a landfill is supposed to stay there, but a new study finds that toxic “forever chemicals” are wafting from the waste into the air.

Per- and polyfluoroalkyl substances, or PFAS, have been detected in the gas exuded by some Florida landfills in quantities comparable to or even greater than in the liquids that seep from the waste, researchers report June 26 in Environmental Science & Technology Letters. These chemicals have been linked to cancer, weakened immune systems, developmental problems in children and a tide of other harmful health effects (SN: 6/15/21). More

The Last DropTim SmedleyPicador, $29.99

A journalist and a farmer visit three fields with different styles of cultivation — conventional, organic and no-till — to bury cotton underwear in each. Though this sounds like the beginning of a bad joke, it’s actually a test of soil health. Healthy soil that produces robust crops holds plenty of water and teems with life that will feast on the undies. This scene is just one of many in U.K.-based journalist Tim Smedley’s book The Last Drop. More

The dry-looking stream in your backyard may play a major role in feeding U.S. rivers.

Channels that flow only in direct response to weather conditions like heavy rain, called ephemeral streams, on average contribute 55 percent of the water in regional river systems in the United States, researchers report in the June 28 Science.

But last year, the U.S. Supreme Court ruled that some waterways — including these streams — are not federally protected from pollution under the Clean Water Act. The decision could have a substantial ripple effect on the environment. More