Text 2. Greenhouse Plants? Vegetation may produce methane

Sid Perkins

Lab tests suggest that a wide variety of plants may routinely do something that scientists had previously thought impossible—produce methane in significant quantities.

Methane, like carbon dioxide, traps heat in Earth's atmosphere. Scientists have been studying natural sources of methane for decades but hadn't pegged plants as a producer, notes Frank Keppler, a geochemist at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Previously recognized sources of methane include bacterial action in the digestive systems of ruminants such as cows and in the saturated soils of swamps and rice paddies.

Now, Keppler and his colleagues find that plants, from grasses to trees, may also be sources of the greenhouse gas. "This is really surprising," Keppler says, because most scientists assumed that methane production requires an oxygenfree environment.

In its experiments, Keppler's team scrutinized the gaseous emissions of a variety of plants and their debris at normal atmospheric oxygen concentrations. A gram of dried plant material, such as fallen leaves, released up to 3 nanograms of methane per hour when the temperature was about 30°C. Each 10°C rise above that temperature, up to 70°C, caused the emission rate to approximately double.

Living plants growing at their normal temperatures generated even larger quantities of methane, as much as 370 ng per gram of plant tissue per hour. Methane emission more than tripled when the plants, either living or dead, were exposed to sunlight.

The team's experiments took place in sealed chambers with a well-oxygenated atmosphere, so it's unlikely that bacteria that thrive without oxygen generated the methane, says Keppler. Experiments on plants that were grown in water rather than in soil also resulted in methane emissions, another strong sign that the gas came from the plants and not soil microbes.

From their data, the researchers estimate that the world's plants generate more than 150 million metric tons of methane each year, or about 20 percent of what typically enters the atmosphere. They report their findings in the Jan. 12 Nature.

"This is some pretty strange chemistry," says David C. Lowe, an atmospheric chemist with the National Institute of Water and Atmospheric Research in Wellington, New Zealand. One reason that scientists hadn't considered plants as a source of the gas is that the laws of thermodynamics don't favor methane production in an oxygen-rich environment. However, Lowe notes, many plants produce volatile hydrocarbons that contribute to haze and smog.

The new finding is an "interesting observation," says Jennifer Y. King, a biogeochemist at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane, they may prevent plant-produced methane from reaching the atmosphere. Field tests will be needed to assess the plants' influence, she notes.

The Keppler team's results may partially explain the large methane plumes recently observed over some tropical forests by Earth-orbiting satellites, says John B. Miller, an atmospheric scientist at the Earth System Research Laboratory in Boulder, Colo. Although such plumes are unsurprising during the rainy season, when methane-producing soil microbes are most active, they also appeared during the dry season.

The new findings will probably spur researchers to revise their models of where and how methane is generated as well as their interpretations of the gas' concentrations measured in ancient ice cores. "This is a big deal if it's real," says Stanley C. Tyler, an atmospheric chemist at the University of California, Irvine.

Text 3. The Continuing Mystery of America's 'Lost Colony'

Written by Jerilyn Watson
15 January 2006

Roanoke Island is off the mid-Atlantic coast of the United States, in North Carolina. In fifteen eighty-seven, more than one hundred people arrived from England to live on the island. Three years later, they were gone. Today we revisit the mystery of whatever happened to America’s "Lost Colony."

Britain’s first settlement of families in America was supposed to be along the Chesapeake Bay. The colonists, however, settled on Roanoke Island instead of sailing farther north. No one knows why.

Roanoke is a low, narrow island between the mainland and the islands of the Outer Banks. The island has thick wetlands, tall oak trees and a lot of wildlife. Today it appears much as it did when the colonists arrived.

The one hundred seventeen men, women and children were not the first white people to try to live on the island. A group of more than one hundred Englishmen had arrived two years earlier, in fifteen eighty-five. But they arrived too late in the year to plant crops, and their supplies nearly ran out. They also fought with Indians. The Englishmen returned home the following year.

Then came the families of what would become the Lost Colony. Governor John White led this group to the New World. Soon, he recognized that the settlers would need more supplies and weapons to survive. So, after only a few months, he decided to return to England.

The Virginia Dare marker at Fort Raleigh

Ten days before he sailed, his daughter Eleanor Dare had a baby girl. Virginia Dare became the first English child born in America.

John White would never know his granddaughter. The last time the governor saw his family was just before he returned to England.

When he arrived in England, John White found himself trapped by the situation there. Britain had declared war with Spain in fifteen eighty. All the ships were sent to battle.

Finally, in fifteen ninety, Governor White returned to Roanoke Island.

But he did not find the small settlement busy and growing. Instead, it was empty. Where could the people have gone? The only evidence was cut into a tree and a fence: the letters C-R-O and the word Croatoan, C-R-O-A-T-O-A-N.

John White thought the colonists had gone to live with the Croatoan Indians south of Roanoke. He was ready to investigate. But a great storm damaged some equipment on his ships. He was forced to return again to England.

The governor tried several more times to go back to America. He never succeeded. John White never knew what happened to the colony or his family.

Historians have theories. Native Americans may have killed the colonists. Or the British could have been killed by Spanish troops who came up from what is now Florida. Or perhaps the settlers went farther inland. There, they might have met friendly Indians and married into their tribes.

The most interesting theory about the Lost Colony started with a rock found in nineteen thirty-seven. The rock was discovered less than one hundred kilometers from Roanoke Island. It was covered with writing. Many people thought it was a message from Eleanor Dare to her father, telling him the colonists fled the island after an Indian attack.

Almost forty other rocks were discovered over the next three years. Together, they told a story of how the colonists traveled, and how Eleanor Dare died in fifteen ninety-nine.

Many historians did not believe the story. But many reporters did. In time, however, an investigative reporter discovered that the whole story was a lie.

As time passed, the settlement itself disappeared. Trees and bushes started to cover the buildings.

In about sixteen fifty-three, a trader named John Farrar and three friends landed on the island from Virginia. Some historians say the group found objects from the Lost Colony and left with them.

In the eighteen sixties, during the American Civil War, Union soldiers won a battle on Roanoke Island. While there, the soldiers apparently dug for evidence of colonial life.

In the nineteen forties, professional archeologists started to investigate the island. But little has been found in recent years.

The Institute for International Maritime Research, based in North Carolina, is looking for more objects from the colonial period. But its director, Gordon Watts, is not digging for the artifacts. Instead, the archeologist is diving for them. The research is part of a project to search on land and in the water for remains of the Lost Colony.

A North Carolina lawyer named Phil Evans organized a group called the First Colony Foundation to raise money for this purpose.

In the nineteen eighties, Mister Evans worked at the Fort Raleigh National Historic Site. During that time, he found what was left of an old well from colonial days. He made this discovery in Roanoke Sound.

Gordon Watts says the sea, over time, may have worn away areas of land. As a result, he says other objects from colonial life may be under the waters of the Roanoke Sound.

Some other experts reject this erosion theory. But National Park Service archeologists did underwater research in two thousand. They found more than two hundred places that might contain historical objects.

Mister Watts and his team have begun work on the northeast side of Roanoke Island. In October of two thousand five, the divers explored an area close to shore. So far, their findings have included pieces of a brick that could be from building materials used in colonial times.

Visitors to Roanoke Island can learn more about the Lost Colony. At the northern end of the island is the Fort Raleigh National Historic Site. This park was developed on the same land used by the colonists.

Objects from the colonial period include an Indian smoking pipe. There are pieces of iron farming equipment. And there are metal counting devices used for keeping financial records.

A model fort is the only structure in the park built in the exact place as the first building. The model was designed to look the same as when those first Englishmen arrived. The fort was mainly a square building with pointed structures called bastions. A bastion is a secure position used for defense against attack.

Inside the visitors center at the Fort Raleigh National Historic Site is the Elizabethan Room. It has wooden walls and a stone fireplace. The fireplace is from a sixteenth-century British home. The Elizabethan Room is similar to rooms in the home of Sir Walter Raleigh. He was a wealthy British investor who supported the settlement of Roanoke Island.

Outside the visitors center are the Elizabethan Gardens, created by the Garden Club of North Carolina. Beautiful paths lead visitors among flowers and plants. People visiting the Elizabethan Gardens can enter through a sixteenth-century garden house.

During summer nights, visitors to the island can see a play called “The Lost Colony.” The Roanoke Island Historical Association has been performing this play since nineteen thirty-seven.

Music and dance tell the mysterious story of the colonists. The show is performed in a historic outdoor theater near the Elizabethan Gardens.

Questions about Eleanor Dare and the other lost colonists continually bring historians and other researchers to Roanoke Island. They hope to discover new evidence about what happened to the young mother and her baby. For now, the mystery of America’s Lost Colony is a story whose ending remains to be written.

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