overpopulationSMALL WORLD: Earth's human population will swell to 7 billion next year, according to a new report from the nonprofit Population Reference Bureau, but that growth isn't being spread evenly across the planet. Africa and Asia are the two fastest-growing continents, and each is expected to add more than 1 billion people over the next 40 years, "exacerbating poverty and threatening the environment" along the way, according to the report. Meanwhile, many developed nations are facing "chronically low birthrates," which the PRB warns "are beginning to challenge the health and financial security of the elderly." Europe will likely be the world's first region to see long-term population declines due to fewer births, but Russia, Japan and South Korea are also expected to shrink. The U.S. population is still rising, however, due to higher birthrates and immigration, and the PRB predicts that, by 2050, the United States will be the only First World country among the global top 10 population leaders. The current top 10 are China (1.3 billion), India (1.2 billion), the United States (310 million), Indonesia (235 million), Brazil (193 million), Pakistan (185 million), Bangladesh (164 million), Nigeria (158 million), Russia (142 million) and Japan (127 million). The world population is now 6.8 billion, already an increase of more than 3 billion in the last 40 years. By contrast, the human population took three centuries to grow from 500 million to 1 billion between the years 1500 and 1800. According to PRB projections, it will reach 8 billion by 2025 and 9.4 billion by 2050. (Sources: New York Times, Economic Times, Columbia University Earth Institute)

great white sharkSHARK WEEK: The Discovery Channel's popular "Shark Week" may not start until Sunday, but great whites off the Massachusetts coast have been getting an early start all month. After weeks of increasing shark sightings in Cape Cod, four 10- to 16-foot great whites were spotted just off shore on Tuesday and Wednesday, and three more showed up Friday — including one that was lurking a mere 100 yards away from a beach party. The shark influx has sightseers pouring into Chatham, Mass., hoping to catch their own real-life sneak peek of Shark Week. "It is jam-packed," the executive director of the local Chamber of Commerce tells the Boston Globe. "There's lots of traffic and shopping coming in. We've experienced lots of people asking about the shark sightings at our visitor's center. It is a big draw today." Of course, soft-bodied primates crowding around razor-toothed killing machines presents some problems, even if only four shark attacks have ever been reported in Massachusetts waters. "This is exciting for us," state marine biologist Greg Skomal tells the Boston Herald, "but good old common sense should kick in." It has, as Chatham authorities decided to close five miles of beach after Friday's triple sighting. Sharks are attracted to the area this time of year because of its growing seal population, and even though Shark Week is tantalizingly close, many beach-goers seem content watching the prehistoric predators through binoculars instead of on TV. "I'd like to see both [sharks and seals], personally," one tourist tells the Globe. "Let's face it, to see a chase would be pretty cool." And while Shark Week lasts only seven days, Cape Cod's great whites "will be here for the next month, maybe two," Skomal adds. (Sources: Boston Globe, MetroDesk, Boston Herald)

IN A PINCH: Blue crab larvae swimming off the Louisiana coast have telltale black-and-orange blobs inside their bodies, and Tulane University researchers say these blobs contain the first clear evidence that an oil-and-dispersant mixture is working its way into the Gulf of Mexico's food web. Biologists began seeing the blobs under young crabs' translucent shells in May, and are still finding them in nearly all the larvae they collect across more than 300 miles of coastline. But the Tulane scientists have taken this observation a step further, using infrared spectrometry to pin down the blobs' chemical makeup — and it carries the chemical signature of Corexit, the main dispersant BP used to break up oil as it gushed from its blown-out Macondo well. "It does appear that there is a Corexit sort of fingerprint in the blob samples that we ran," Tulane biologist Erin Gray tells the Huffington Post. Two independent tests are being conducted to confirm those findings, and while Tulane biology professor Caz Taylor says the chemistry test "is still not completely conclusive," she adds that Corexit "seems the most likely" culprit. This isn't just bad news for blue crabs, though — they serve as meals for a wide array of Gulf animals, many of which must already be unwittingly gulping down crude and Corexit with every bite of blue crab. Oil is toxic on its own, and the toxic properties of Corexit remain a mystery, especially at such a large scale and combined with oil. The dispersant also acts as a "delivery system" for oil, says Susan Shaw, director of the Marine Environmental Research Institute: "The properties that facilitate the movement of dispersants through oil also make it easier for them to move through cell walls, skin barriers, and membranes that protect vital organs, underlying layers of skin, the surfaces of eyes, mouths, and other structures." (Source: Huffington Post)

SPILL ON THE HILL: The U.S. House of Representatives will vote soon on a bill that would tighten the reins on offshore drilling, part of an effort to crack down on oil companies in the wake of the Gulf oil spill. The measure is expected to pass, allowing lawmakers to return home during a six-week August recess boasting that they took Big Oil to task and helped prevent another catastrophic spill. That could offer a boost for some Democrats in an election year that likely won't be kind to the party in power, but the legislation would still have an uphill battle before becoming law. The Senate is currently mulling its own version of the bill, introduced earlier this week by Senate Majority Leader Harry Reid, D-Nev., and its success before the Aug. 6 recess is much less certain. A major sticking point in the Senate is the removal of a liability cap for oil companies, which Democrats are advocating as a way to retroactively ensure BP's liability for the Gulf spill doesn't stop at $75 million, the current cap. Republicans and even BP have agreed that $75 million is too low, but some critics of scrapping the cap argue that limitless liability would scare smaller companies away from offshore drilling, giving a virtual monopoly to large multinational firms like BP. Yet even though BP has pledged to pay all costs related to the spill, many lawmakers want to prevent a drawn-out process similar to the decades of litigation that followed 1989's Exxon Valdez spill in Alaska. In addition to the liability measure, the House bill also address offshore drilling safety and the use of chemical dispersants, among other issues. (Source: Reuters)

TREE FARMERS: Trees growing in nutrient-poor forest soils can "farm" specific soil bacteria to help their roots get a balanced diet, according to a new study published in the journal Applied and Environmental Microbiology. Certain bacteria are more efficient at breaking down inorganic minerals into usable nutrients, a process known as "mineral weathering" that's especially important in acidic forest soils. A lack of adequate nutrients can be a huge hurdle for up-and-coming trees, and to overcome this subterranean shortage, some tree species have apparently learned to cultivate the right microbes to help them milk the most out of the dirt around them. This has major implications for the makeup of forest soils, the researchers say, especially as climate change begins tweaking regional temperature trends, potentially altering weather patterns that can affect trees' survival. "This question regarding the impact of tree species on the functional diversity of the bacterial communities remains a major issue in forestry, especially in the context of today's climate change, which will give rise to a shift in the spatial distribution of forest tree species," says study co-author Stephane Uroz. Of the trees studied, oak and beech showed the most mineral-weathering bacteria around their roots, while Norway spruce showed very little. (Source: ScienceDaily)

Russell McLendon

Want to receive the day's eco-news in your inbox? Click here to sign up for the Daily Briefing newsletter.

Photo (crowd of people): ZUMA Press

Photo (great white shark): ZUMA Press

Photo (blue crab larvae with oil and dispersants): Erin Gray/Tulane

Photo (U.S. Capitol building): ZUMA Press

Photo (trees and sunlight): U.S. Global Change Research Program

Russell McLendon ( @russmclendon ) writes about humans and other wildlife.