America’s Billion-Dollar Tree Problem Is Spreading

Fast-growing, drought-tolerant trees are slowly spreading across grasslands on every continent except Antarctica. Given how desperate we are to reduce carbon in the atmosphere, millions of new saplings sprouting each year might seem like a good thing. But in reality, their spread across vulnerable grasslands and shrublands is upending ecosystems and livelihoods. As these areas transform into woodland, wildlife disappears, water supplies dwindle, and soil health suffers. The risk of catastrophic wildfire also skyrockets.

In a new study published in the Journal of Applied Ecology, researchers have shown how woodland expansion also takes an economic toll. American ranchers often depend on tree-free rangelands to raise their livestock. Between 1990 and 2019, landowners in the Western US lost out on nearly $5 billion worth of forage—the plants that cattle or sheep eat—because of the growth of new trees. The amount of forage lost over those three decades equates to 332

Air Quality Mirrors the Racial Segregation of US Neighborhoods

Racial inequity biases algorithms, skews Covid-19 death rates, and exacerbates the digital divide. Your race is even a good predictor of what’s in the air you breathe—and now, a new study shows that those pollution concentrations are also tied to how segregated your community is.

Using five years’ worth of data, a team led by scientists at Colorado State University confirmed a long-suspected link between ambient air quality and racial residential segregation. In a recent paper published in Nature Communications, they show that people in highly segregated counties in the United States are exposed to more fine particulate matter, airborne particles that are less than 2.5 micrometers in diameter (or PM 2.5 for short). What’s more, the makeup of that pollution contains higher toxic metal concentrations than what is found in well-integrated areas. The results are congruent with a growing number of studies showing that people of color are

Tiny Aerosols Pose a Big Predicament in a Warming World

Fossil fuels are rapidly warming the planet, and the aerosols from their combustion kill millions of people each year. So we need to rapidly decarbonize. But in an ironic twist, those aerosols actually have one beneficial side effect: They cool the atmosphere. It creates an odd climate contradiction. If we burn less gas, oil, and coal, we’ll stop loading the sky with planet-warming carbon, but we’ll also load it with fewer planet-cooling aerosols. 

But exactly how much cooling we get from aerosols, and how strong that effect will be as the world weans off fossil fuels, are huge questions among climate researchers. “It’s taken as read that aerosols are important,” says University of Oxford climate scientist Duncan Watson-Parris. “And this uncertainty in the aerosol effect is a key uncertainty in climate science.”

Last week, Watson-Parris published a paper in the journal Nature Climate Change in which he played

A New Explanation for How Fireflies Flash in Sync

A similar scenario played out in the 1990s, when a Tennessee naturalist named Lynn Faust read the confident published assertion of a scientist named Jon Copeland that there were no synchronous fireflies in North America. Faust knew then that what she had been watching for decades in the nearby woods was something remarkable.

Faust invited Copeland and Moiseff, his collaborator, to see a species in the Great Smoky Mountains called Photinus carolinus. Clouds of the male fireflies fill forests and clearings, floating at about human height. Instead of blinking in tight coordination, these fireflies emit a burst of quick flashes within a few seconds, then go quiet for several times that long before loosing another burst. (Imagine a crowd of paparazzi waiting for celebrities to appear at regular intervals, snapping a salvo of photos at each appearance, and then twiddling their thumbs in the downtime.)

Copeland and Moiseff’s experiments

The Marine Lab in the Path of Climate Change’s Fury?

This story originally appeared on Hakai Magazine and is part of the Climate Desk collaboration.

As the storm first gathered strength in the Gulf of Mexico, its future path was indecipherable. Its capacity for damage, though, was clear. The water was warm and the air was thick and humid—the recipe for a potentially historic tempest. On Thursday, August 26, 2021, just hours after the system was classified as a tropical depression, Louisiana’s governor declared a state of emergency: Every resident along the state’s coastline needed to prepare for a major hurricane.

Louisiana is protected by a series of levees that zig and zag along the coastline—walls of earth meant to block hurricane-driven waves from reaching the state’s bigger towns and villages. Floodgates clasp shut so that local bayous don’t overflow with storm surge. By necessity, though, the DeFelice Marine Center stands outside this system of defenses.

The building—a roughly 7,000-square-meter