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Tree Diaries

© Debbie St. Germain

One hundred and twenty colonists settled on the island of Roanoke, which is off the coast of North Carolina. It was decided that the governor, John White, would return to England to bring back more supplies. Upon his return to Roanoke Island after a three-year absence, the governor found the island deserted. There were no signs of a battle or fire, only weeds covering the ground where the buildings once stood.

The case of the missing settlers has been a mystery since 1597. If only a journal had been left by one of the settlers, we might know of their whereabouts. The settlers may not have left a diary of their stay, but what was left was a tree diary.

For thousands of years, diaries have been kept by trees in the form of tree rings. By studying tree rings, researchers may have found an answer to the disappearance of the settlers on Roanoke Island. The mystery is being solved by a group of dendrochronologists: people who study tree rings. Their study has indicated that there was a severe drought in the 16th century that would have wrecked havoc in the lives of the early Spanish and English settlers.

Using drought-sensitive tree ring chronologies that extend back before A.D 1500, they found that dry conditions extended throughout parts of Mexico, the Southwest, the Rocky Mountains, and into the Mississippi Valley throughout the last half of the 1500's.

The researchers have looked back as far as A.D 1200 and no other drought appears to have been as intense, prolonged and widespread as the 16th century megadrought. The tree-ring records show that this was the worst drought in 1,000 years; and in some places this dryness lasted 40 years.

Records from another colony on Parris Island, which is also off the coast of North Carolina, indicate a severe drought from 1566 to 1569. The same year that the colonists on Roanoke Island disappeared, the Parris Island settlers abandoned their colony, because of the drought. The tree-ring data from that particular area show that it was the region's worst drought in 800 years.

Tree growth depends on the amount of water and nutrients the tree receives. Researchers can tell about a region's climate history by looking at the recorded tree ring growth from year to year using pencil-thin core samples from living trees. This field of study, known as dendrochronology, was begun in the early 1900's by an American astronomer named Andrew Ellicott Douglass.

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