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The number of visitors to California's Yosemite National Park has swelled to four million a year. Now scientists think the impact of so many human beings is rippling among the web of organisms in the park, from cougars to mule deer all the way down to the park's signature wildflower, the evening primrose.

Although many of the Yosemite's cougars were shot by park officials in the 1920's, some of these predators remain. Yet they seem to avoid Yosemite Valley, the picturesque main entrance to the park that is home to numerous roads and buildings. The deer recognize this safe haven, says Oregon State University forestry scientist William Ripple. "We think the deer are moving closer to where the humans are." The many mule deer browse heavily on young California black oak and primrose in Yosemite Valley, and the plants are often unable to reach reproductive age. Ripple and his colleagues noticed that oak trees away from the visitor center were taller and more abundant.

By pushing predatory cougars out of the valley, humans have indirectly increased mule deer and reduced oak and primrose populations. This is an example of a trophic cascade—one that appears to be reducing biodiversity in one of the nation's most spectacular landscapes.

The Northern California coast is home to giant redwoods —the tallest trees in the world. The towering evergreens depend on the region's foggy climate, especially during the hot summer months. When rainfall is insufficient to hydrate the trees from the roots, the trees quench themselves by drawing moisture into their leaves from the fog.

Researchers at the University of California--Berkeley recently analyzed the frequency of coastal fog over the past hundred years. They discovered many fluctuations in fog and an overall decline. Scientists are unsure of what has caused these changes. The team's ongoing research will study how the redwoods will likely respond to variations in the climate they rely on.

China has 20 percent of the world's population but just 7 percent of its arable land. Chinese farmers have, for decades, relied upon artificial fertilizer to boost their crops. These artificial fertilizers, while increasing overall crop yields, can also upset the chemical balance in the soil and cause it to become more acidic. Recently, researchers compared samples of Chinese soil from the 1980's and the 2000's and found that agricultural lands across the country have become considerably more acidic. This chemical imbalance may reduce the farming potential of this land in the future.

In the rock layers of a vast open-pit coal mine in Colombia, paleontologists have uncovered a fossil of the largest snake known to have existed. The massive 60,000,000-year-old vertebrae suggest that the creature was about as long as a bus and three feet thick. The discovery team, composed of researchers from Canada, Panama, and the United States, named the snake Titanoboa cerrejonensis ("titanic boa from Cerrejón") after its size, its close relatives, and the name of the mine. Researchers think Titanoboa would likely have been too large to climb trees like modern boa constrictors. Instead, it probably sought its crocodile prey while swimming through the myriad rivers that cut through its forested coastal habitat.

Beyond being a winning entry in the animal record books, the snake is also a measuring stick for ancient tropical climate. Because the maximum body sizes of some snakes, turtles, crocodiles and other cold-blooded creatures are regulated by the temperature of their surroundings, their size can be used as a temperature gauge. The researchers estimate that the region averaged at least 30-34°C (86 -93°F) 60 million years ago, giving a new data point from which to compare tropical temperature change over time.

Astronomers from the University of California, Berkeley and the Institut de Mécanique Céleste et de Calculs des Éphémérides (IMCCE) in France, recently captured the best view yet of the dog-bone-shaped asteroid Kleopatra. Using the Keck II telescope and a technology known as adaptive optics, which reduces the distortion of light by Earth's atmosphere, the researchers were able to resolve Kleopatra's two small moons—a rare find among asteroids that can provide clues to planet formation.

The new VISTA telescope is taking a fresh survey of the Southern Hemisphere sky by examining infrared radiation. Some of the first images released from the powerful telescope focus on the Orion Nebula. From Earth, the nebula is visible to the naked eye, but cosmic dust blocks much of the view in visible wavelengths of light. VISTA's infrared view has revealed what glows beneath the dark, dusty regions in the famous nebula.

This visualization shows the growth of impervious surfaces between 1986 and 2000 as measured by researchers using satellite imagery. These images were produced as part of a study of the effects of urban sprawl on ecosystems in the mid-Atlantic region. Such information is essential for residents, government officials, managers, scientists, and other concerned citizens to understand and solve the problems introduced by urban sprawl.

In 1980 an act of Congress set aside nearly 20 million acres of Alaska's North Slope tundra to create the Arctic National Wildlife Refuge (ANWR). Less than 100 miles from the refuge is Prudhoe Bay, North America's largest oil field. Spread across what was once part of the largest intact wilderness area in the United States, Prudhoe Bay and its neighboring oil fields account for approximately 25 percent of U.S. domestic oil production.

In section 1002 of the Alaska National Interest Lands Conservation Act, which created ANWR, Congress deferred a decision regarding future management of 1.5 million acres of North Slope coastal plain (called the 1002 area) in recognition of the area's potential as an oil and gas reserve as well as its significance as a unique wildlife habitat, home to polar bears, grizzly bears, musk oxen, caribou, and some hundred and thirty-five species of birds.

As global fears of a disrupted and dwindling oil supply mount, the debate over the fate of the 1002 area is raging. The option of opening ANWR to oil leasing has become a political hot potato, hardly a climate conducive to calmly weighing the information and options that lie ahead. Political rhetoric aside, the evidence provided by all sides seems contradictory not just in perspective, but in facts. From widely disparate estimates of recoverable oil to contrasting predictions of exploration's impact on the land, it remains hard to decipher just what's at stake when it comes to drilling for oil in the Arctic National Wildlife Refuge.

The landscape of human language is complex. Tracing the origins of the 7,000 known modern languages has been a significant challenge for scientists, but a novel new analysis by a researcher at the University of Auckland in New Zealand points to a familiar place: Africa, the birthplace of our species.

This fall, examine the biology of language in a five-part adult course, the Sackler Brain Bench program "Is Your Brain Wired For Language?" For more information, visit: http://www.amnh.org/calendar/is-your-...

Scientists have released the largest survey yet of human genetic variation.

The human body is a diverse bacterial ecosystem. Humans are hosts to trillions of microbes, most of which are harmless or even beneficial. But a new study shows how one bacterium traveled from humans to farm animals and back to humans, developing resistance to antibiotics along the way. Staph infections in humans are usually treatable, but this new strain, called methicillin-resistant Staphylococcus aureus (MRSA), does not respond to antibiotics. Researchers found that it developed resistance while in farm animal hosts, through exposure to high level of antibiotics in their diet. Identifying the evolutionary processes of disease agents that transfer between species may help scientists determine how to prevent and treat emerging diseases.

Related Links:

Staphylococcus aureus CC398: Host Adaptation and Emergence of Methicillin Resistance in Livestock
http://mbio.asm.org/content/3/1/e0030...

PubMed Health: MRSA
http://www.ncbi.nlm.nih.gov/pubmedhea...

CDC: Methicillin-resistant Staphylococcus Aureus (MRSA) Infections
http://www.cdc.gov/mrsa/

US Food and Drug Administration
http://www.fda.gov/

New York Times: Steps Set for Livestock Antibiotic Ban
http://www.nytimes.com/2012/03/24/hea...

The rising temperatures of global climate change are melting the world's ice. Most notable are the shrinking ice sheets of Greenland and west Antarctica, which have shown dramatic loss in recent years. Travel to the glaciers of Greenland and to fossilized coral reefs of the Florida Keys, where earth scientists are studying geologic records of past warming to predict future ice loss and associated sea level rise.

The unicellular amoeba Dictyostelium discoideum has long been a staple study organism in research laboratories, but the latest discovery about "Dicty" came as a surprise. Scientists from Rice University in Houston, Texas, found that a third of wild specimens are able to sow and harvest the soil bacteria they rely on for food.

The MESSENGER satellite left Earth in 2004 and began its orbit around Mercury on March 17, 2011. New images show areas of the planet's surface never seen at close range. Over the next year MESSENGER will map the entire surface of the planet and send back other valuable data.