Early American colonists 'were hit by severe drought'

A study of discarded oyster shells have reinforced the idea that the first British colonists in America had to endure an unusually severe drought.

Founded in 1607, was Jamestown in Virginia the first successful English settlement in North America.

Chemical analysis of shells discarded from 1611-1612 shows that the James River, where oysters were harvested were much saltier then than it is today.

This was due to reduced flow from the surrounding freshwater rivers.

For this to have been the case, the rainfall was much lower when these oysters were growing.

U.S. researchers have published details about the work of the Proceedings of the National Academy of Sciences (PNAS) journal.

After sailing from London, selected colonists Jamestown Island on the James River (named in honor of their king) as a safe place for their solution.

The location had the advantage of a deep water channel allowing English ships to ride close to shore.

But the island was swampy and overrun by mosquitoes.
And the latest evidence, combined with previous data, but the colonists could not have picked a worse time to establish their settlements.

Juliana Harding from the College of William and Mary at Gloucester Point, USA, and colleagues analyzed the oyster shells retrieved in 2006 from a well dug by the colonists.

The well was in use for only a short time before being converted into a dirt pit, either because it ran out or were infiltrated by salt water.

The team looked at levels of a certain isotope, or form of oxygen that is provided in the tanks.
The levels of this isotope - known as oxygen-18 - in oyster shells is controlled by temperature and salinity in the water they grow in.

The team compared oxygen-18 values in the 17th century James River oyster shells with them from their modern counterparts.

They found that winter salinity of the river was much higher in the early 1600s than it is today.

This suggests that winter precipitation was significantly lower than modern levels, confirming historical accounts of drought conditions at that time.

Previous data based on tree rings and historical documents show that the arrival of the English colonists in Virginia with a strong regional drought.

In the years 1606-1612 was the driest in nearly eight centuries.

"Shortages of food and fresh drinking water, combined with bad leaders, nearly destroyed the colony during its first decade," the authors of the recent study write in PNAS.

During what became known as "starving time" from 1609-1610, of which 80% of the colonists died.

Seasonal cycles of oxygen-18 values, together with archaeological data, allowed the researchers to demonstrate that the oysters were collected in different seasons between 1611 and 1612.