Yellowstone’s roaming bison herds enhance nutrient cycles and boost ecosystem health at landscape scales, according to a new study. The findings, which challenge conventional grazing wisdom, suggest that restoring large-scale migrations could unlock the species’ full ecological power. Historically, North America supported tens of millions of bison whose seasonal migrations transformed the continent’s vast grassland ecosystems. Today, these once massive herds of wild, free roaming bison are no more; only about 400,000 bison remain, and almost all exist in small managed herds on private land or within parks and reserves. Although research suggests that bison play a powerful role in shaping ecosystems by diversifying habitats, influencing plant communities, and driving processes like nutrient cycling and productivity, the broader ecological impacts of large, migrating herds remain poorly understood because modern bison are mostly confined to limited areas. The restoration of bison migrations in the northern Yellowstone ecosystem, however, provides a rare natural laboratory for understanding how large herbivores shape ecosystems at the landscape scale.

Between 2015 and 2022, Chris Geremia and colleagues tracked bison grazing dynamics across 16 sites representing the animal’s three main habitats, and measured their impact on carbon and nitrogen dynamics, plant communities, and soil microbiology. Geremia et al. found that bison stabilized plant production while accelerating nitrogen cycling, boosting aboveground nitrogen and improving landscape nutritional quality, particularly in wet, nutrient-rich areas that hosted bison densities and grazing at levels higher than typically recommended. Soil microbe density and nitrogen content in soils and plants also increased in grazed areas. According to the authors, the findings show that the ecological power of large, migrating herbivores lies not only in their size but in their numbers, density, and freedom to migrate. “To move forward with conserving migratory herbivores and grassland ecosystems, we must embrace landscape-scale heterogeneity – not at the scale of individual ranches or pastures, but at sizes that allow for thousands of migrating large herbivores to move freely across the landscape,” write Geremia et al. “Our findings emphasize that ecosystems with large native herbivores, such as bison, can function successfully in today’s world.”

The Tijuana River’s polluted waters don’t just contaminate Southern California’s beaches – they also release toxic gases and aerosols that travel far beyond the riverbanks, threatening the health of nearby communities, according to a new study. The Tijuana River Valley, straddling the US-Mexico border, faces a severe and worsening pollution crisis as untreated sewage, industrial waste, and toxic runoff flow into the Pacific, causing prolonged beach closures and persistent environmental health risks. While most concern has centered on direct contact with contaminated water, mounting evidence shows pollutants can aerosolize, becoming airborne and dispersing far beyond the riverbanks. This overlooked pathway means communities may face greater exposure through inhalation than through direct contact with contaminated water. With over half the global population living near waterways, understanding the impact of water pollution on air quality is an urgent yet understudied public health priority.

Building on previous research that traced airborne bacteria and chemical pollutants near the mouth of the Tijuana River in San Diego, California, and guided by community reports of foul odors and health symptoms of those who live near the river, Benjamin Rico and colleagues identified a turbulent stretch of the river as a likely hotspot for gas and aerosol emissions. This prompted the authors to use a mobile air quality lab to measure hydrogen sulfide (H₂S) – a toxic gas produced by the breakdown of sewage – as an airborne tracer of water pollution. They found that the record high dry-season flows of 2024 led to a significant spike in H₂S emissions, with nighttime peaks reaching 4500 parts per billion (ppb) – thousands of times above typical urban levels (<1 ppb). According to Rico et al., the findings highlight the impact that turbulent portions of contaminated rivers have on regional air quality. Because existing air quality models omit emissions from polluted rivers and estuaries, incorporating these pathways is critical for accurately predicting health impacts, addressing inhalation risks, and guiding mitigation. Moreover, the exceedingly high H₂S concentrations confirmed the validity of long-dismissed community observations, highlighting the disproportionate burden borne by marginalized communities. “Sustained monitoring, coordinated cross-border efforts, and leadership from federal, state, and local authorities are crucial to finally provide the protection and justice long denied to communities affected by this ongoing environmental and public health crisis,” Rico et al. write.

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When genetic testing reveals a rare DNA mutation, doctors and patients are frequently left in the dark about what it actually means. Now, researchers at the Icahn School of Medicine at Mount Sinai have developed a powerful new way to determine whether a patient with a mutation is likely to actually develop disease, a concept known in genetics as penetrance. The team set out to solve this problem using artificial intelligence (AI) and routine lab tests like cholesterol, blood counts, and kidney function. Details of the findings were reported in the August 28 online issue of Science. Their new method combines machine learning with electronic health records to offer a more accurate, data-driven view of genetic risk.