Cities have experienced an unprecedented rate of growth in the last decade. More than half the world's population lives in urban areas, with the U.S. percentage at 80 percent. Cities have captured more than 80 percent of the globe's economic activity and offered social mobility and economic prosperity to millions by clustering creative, innovative, and educated individuals and organizations. Clustering populations, however, can compound both positive and negative conditions, with many modern urban areas experiencing growing inequality, debility, and environmental degradation.

pH is a measure of how acidic/basic water is. The range goes from 0 to 14, with 7 being neutral. pHs of less than 7 indicate acidity, whereas a pH of greater than 7 indicates a base. The pH of water is a very important measurement concerning water quality.

The mouth of Bayou St. John, for a cast of officials from the Army Corps of Engineers and Orleans Levee District, represents more than anything a point of vulnerability. Their priority is simple: keep storm surge from Lake Pontchartrain at bay, and prevent the transformation of a natural waterway into a highway for delivering floodwater to New Orleans' heart. But for an increasingly vocal alliance of New Orleanians, the junction of the bayou and the vast lake represents much more than a flood protection issue.

This island will cease to exist. That much seems certain. Over the last six decades, more than 98% of Isle de Jean Charles has vanished into the Gulf of Mexico, leaving a frail strip of land just two miles long and a quarter-mile wide. With each high tide and with each hurricane, a little more of this historic Native American land sinks below the surface. Cow pastures are gone. Rice fields are gone. The encroaching saltwater seeps into the roots of the towering live oaks that loom over the bayou, transforming them into eerie gray skeletons.

Most nonpoint source pollution occurs as a result of runoff. When rain or melted snow moves over and through the ground, the water absorbs and assimilates any pollutants it comes into contact with. Following a heavy rainstorm, for example, water will flow across a parking lot and pick up oil left by cars driving and parking on the asphalt. When you see a rainbow-colored sheen on water flowing across the surface of a road or parking lot, you are actually looking at nonpoint source pollution.

While it may seem like a straightforward planting project, this restoration highlights the connections between human society and the ecologies we depend on. The tribe's millennia-long relationship with the land inspired members to join the volunteer crews each year. Every October, they mark the cranberry harvest with a festival celebrating the significance of their entanglement with the land. The planting days have built relationships between the tribe and other civic organizations.

Anchovies are known more as a pickled pizza topping than for their crucial place in the marine food chain. Now scientists have confirmed a disturbing new behavior by these tiny forage fish that could have larger implications for human health: anchovies are eating tiny pieces of ocean plastic, and because they, in turn, are eaten by larger fish, the toxins in those microplastics could be transferred to fish consumed by humans.

Researchers in France said this week that they found thousands and thousands of microplastic particles raining down on a secluded spot in the Pyrenees, 75 miles from the nearest city. Their study, published in the journal Nature Geoscience, suggests that microplastics - long known as a source of water pollution - may also travel by air, spreading their ill effects far from dense population centers.

Plastic in our oceans has clear detriments to the ecosystems inhabiting them; nearly 700 marine species are reported to have encountered plastic debris, which can lead to entanglement, ingestion, or death. Protecting marine life from further harm caused by plastic pollution is the main driver behind our mission to rid the oceans of plastic. At the same time, we need to ensure that our cleanup operations have minimal negative side effects on marine ecosystems.

This article features interactive materials that allow the reader to investigate how climate change will impact individual counties throughout the United States. "Taken with other recent research showing that the most habitable climate in North America will shift northward and the incidence of large fires will increase across the country, this suggests that the climate crisis will profoundly interrupt the way we live and farm in the United States.