Weatherwatch: the Irish potato famine

Stephen Moss looks at how weather caused famine in mid-19th century Ireland

As the potato harvest began in Ireland in 1845, prospects were looking good for a bumper crop. This was just as well, for Ireland's population had increased dramatically in the previous decades to more than 8 million. But when people dug up the potatoes, all they found was a black sticky mess – the result of potato blight.

Potato blight is a disease whose spores are carried in the air. It is estimated that less than half the potato crop that year was edible, and the following two years saw renewed outbreaks. The blight was not confined to Ireland, it also reached southern Britain and the Low Countries. But the combination of a soggy climate, and the dependence on the potato as a staple diet, meant that the Irish suffered far more than most.

The resulting famine changed both Ireland and the rest of the world. More than one million people died of starvation, and another million emigrated, mostly to the US. Political and economic factors were certainly to blame for the devastating effects of the blight. But the catalyst that enabled it to spread was the weather. Ireland has a damp, maritime climate, thanks to its geographical position on the extreme western edge of the Eurasian landmass, jutting out into the Atlantic Ocean.

The summer of 1845 was especially wet, with high humidity – ideal conditions for the spores of the blight to develop on the leaves. Persistent rain then washed them into the soil, where they infected the growing potato tubers.

• This article was amended on 25 September 2011. The original put Ireland's population in 1845 at more than 3 million. This has been corrected.

Contributor

Stephen Moss

The GuardianTramp

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