April 28, 2014

The entire state of California is now suffering from moderate to exceptional drought conditions, according to a recent report from the United States Drought Monitor (USDM). The drought is the worst in the 15-year history of the USDM, which is a joint project by the National Drought Mitigation Center, the National Ocean and Atmospheric Agency, the U.S. Department of Agriculture, and drought observers across the country. The USDM found that the area of California experiencing “extreme drought” has jumped from zero percent in April 2013 to 76.68 percent this month. The area experiencing “exceptional drought” has risen from zero percent to 24.77 percent during the same period. Government officials are deeply concerned about the effect of the drought on drinking water for California communities as well as the state’s valuable agricultural industry. California produces more agricultural products than any other U.S. state. A vast farming region, the Central Valley, is the leading region in the United States for growing fruits, nuts, and vegetables.

Although winter is normally California’s wettest season, 2013 was the driest year in that state’s recorded history, the U.S. National Weather Service (NWS) has reported. The state’s snowpack (snow that accumulates on mountaintops during the winter) was measured at less than one-third of its historical average, according to April data collected by NASA‘s Airborne Snow Observatory.

All of California is now experiencing drought. (U.S. Drought Monitor)

The immediate cause for California’s parched condition is a weather phenomenon that meteorologists have nicknamed the Ridiculously Resilient Ridge. This massive wall of high-pressure air is nearly 4 miles (6.4 kilometers) high and 2,000 miles (3,200 kilometers) long. The ridge, which developed in December 2012, has prevented Pacific winter storms from coming ashore in California. Instead, the storms have been deflected to Alaska and British Columbia. “It’s like the Sierra–a mountain range just sitting off the West Coast–only bigger,” Bob Benjamin, a NWS forecaster told the San Jose Mercury News. “This ridge is sort of a mountain in the atmosphere. In most years, it comes and goes.” This time, however, it came and stayed. Some scientists have speculated that climate change may be keeping the ridge in place.

Additional World Book articles:

• Irrigation
• Losing Ground (a Special Report)
• Parched Earth (a Special Report)

July 31, 2013

Weeks of spring and summer rains across the southeast United States have severely affected crops dependent on hot summer sun. Peaches are tasteless; tomatoes are splitting; and watermelons are rotting on the vine. Watermelon farmers in southern Georgia believe that at least half of their crop is lost. In North Carolina, rain delayed spring planting of the peanut crop, which agronomists say will undoubtedly result in lower yields.

While rainfall across the contiguous 48 states is only about 6 percent above normal for this time of year, the Southeast has been swamped. According to the National Climatic Data Center, rainfall in Georgia through June was 34 percent above normal; North Carolina and South Carolina were 25 percent above normal; and Alabama was 22 percent above normal. By contrast, the region was abnormally dry or in drought at this time last year.

Weeks of rainstorms have severely affected crops across the Southest. (© Marco Alegria, Shutterstock)

State officials in the Southeast predict agricultural losses will mount into the billions of dollars this year. In some areas, water is standing in cornfields, and mold is growing on the stunted ears of corn. Tomato fields are being hit by late blight, a fungus-like pathogen. Pecan farmers fear that a rain-related fungus, scab disease, will cut crop yields by as much as 15 million pounds (6.8 million kilograms). This year’s Georgia beach crop is essentially lost because the rain has diluted the sugar content of the fruit. “The flavor is just not there,” one farmer told The New York Times. “It’s like having a mouthful of cotton.”

On top of compromising quality and fostering disease, the rains have left the ground so wet that farmers may be unable to get equipment into the fields to harvest. Climatologist Jake Crouch, with at the National Climatic Data Center in Asheville, North Carolina, is not hopeful about a drier late summer and fall. “Whenever we get in a pattern like this, we kind of stay in the status quo,” Crouch reported to the Times. “When we’re hot and dry, we stay hot and dry. When we’re wet, we stay wet.”

Additional World Book articles:

• Agriculture
• Climate
• Weather
• Agriculture 2012 (a Back in Time article)
• When the Rain Stops (a special report)

April 26, 2013

The genetic roots of modern Europeans do not stretch as deep into prehistory as most scientists had thought, reports a joint team of German and Australian scientists. A new analysis of ancient skeletons found in Germany indicates that a major population upheaval occurred in Europe around 4,000 B.C., when long-established populations were suddenly displaced by other farming people moving into the region. These more recent migrants, rather than the older populations, seem to be the direct ancestors of most living Europeans today.

Archaeologists have found fossils and stone tools that show early humans first lived in Europe more than 700,000 years ago. The Cro-Magnon people hunted throughout Europe from about 35,000 years ago to 10,000 years ago. By about 6000 B.C., farming peoples migrated into Europe from the Near East. Most scientists had believed that modern Europeans were descended from these ancient populations. The new findings, however, suggest that most living Europeans are descended from farmers who migrated into the region only about 4,500 years ago.

A megalithic monument near Carnac, France, is one of many of these stone structures made by prehistoric people. The best-known monuments are in western Europe and the Mediterranean region. These sites were built between about 4500 and 1400 B.C., during the Neolithic period and early Bronze Age. The builders made them for religious purposes or as burial places. (© Joe Cornish, Tony Stone Images)

The scientists based their conclusions on an analysis of DNA from 39 ancient skeletons excavated from the Mitelelbe Saale region, near Lepzig. The analysis was published April 23 in the online journal Nature Communications. The team focused their study on mitochondrial DNA (mtDNA)–a form of DNA found outside the chromosomes in cellular structures called mitochondria–that was preserved in the bones. In humans, mtDNA is inherited only from the mother. This makes the material useful to biologists for helping to determine relationships between groups. The scientists chose to examine a particular variety of mtDNA known as haplogroup H, the most common mtDNA variety in Europe, found in about 40 percent of Europeans today. However, haplogroup H is not common in the mtDNA from skeletons of Cro-Magnons or other early European hunter-gatherers, suggesting they made little genetic contribution to modern European populations.

The mtDNA from skeletons dated to the early Neolithic period of Europe, about 7,500 years ago, shows that farmers from the Near East migrated into Europe carrying a version of the haplogroup H with them. However, the international team found that by the Middle Neolithic, around 4,500 years ago, this early version of haplotype H was suddenly replaced by the version seen in modern Europeans.

Scientists are not certain where this newer haplotype H originated. But such a rapid replacement could only result from the migration of new populations into the region. The research shows that the movement of populations in prehistory and the genetic history of modern populations is much more complex than scientists had thought.

Additional World Book articles:

• Agriculture (History)
• Cave dwellers
• Genetics
• Prehistoric people
• Stone Age