In presenting historical interpretations of what really happened at jamestown, jeffery sheer referenced dennis blanton who suggested

Environmental factors affected Jamestown. There were shorter-term oscillations in the regional climate such as drought and periods of cold. The period coincided with a cool spell in North America and western Europe known as the so-called Little Ice Age. This period was not one of constant cold, but instead there were more frequent and extreme intervals of low temperature. Moreover, during the first years of the colony  a severe drought complicated life for the early settlers.

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