There are many reasons why people should migrate in huge numbers. But new research pinpoints what may drive climate migrants.

LONDON, 26 November, 2017 – German scientists say climate migrants may be responding to a range of pressures, and not just to climate change alone.

They have established a clear link between climate change and migration: it happened during the 19th century, when temperatures fell and harvests failed. And then it happened again, when temperatures rose and drought scorched the cereal crops. And in both cases, many of the migrants moved to America.

Researchers report in the journal Climate of the Past that after the notorious “year without a summer” in 1816, a year in which a volcanic eruption in Indonesia darkened the skies worldwide, statistics from what is now Baden-Württemberg in Germany reveal a wave of migration to the US. It happened again in 1846, after a prolonged hot and dry summer.

But although weather affected harvests between 1850 and 1855 the evidence was less clear that climate drove migration: during those years the French banned food exports – because of the Crimean War – forcing up the price of grain in Germany.

Partial explanation

“Overall, we found that climate indirectly explains up to 20-30% of migration from southwest Germany to North America in the 19th century,” said Rüdiger Glaser, of the University of Freiburg, who led the research.

“The chain of effects is clearly visible; poor climate conditions lead to low crop yields, rising cereal prices and finally emigration. But it is only one piece of the puzzle.”

Climate scientists have been warning for years that climate change could drive mass migration and may already be doing so.

Researchers have warned that by 2100, up to 2bn people could become climate refugees, and at around the same time conditions in some parts of North Africa and the Middle East may become intolerable, creating pressure for a mass exodus.

And even within the United States, researchers have warned of huge numbers of internal migrants, forced to flee the flooded coastal cities.

“The chain of effects is clearly visible; poor climate conditions lead to low crop yields, rising cereal prices and finally emigration. But it is only one piece of the puzzle”

But it is one thing to forecast the consequences of climate change, another to demonstrate that the climate itself will be the driving force. Many refugees trying to reach Europe from Iraq, Libya and Syria have been forced from their homes by conflict, which itself might be linked to climate change.

And people abandon their homes for a mix of reasons. What Professor Glaser and his colleagues have done is spell out a clear link between climate and successive waves of migration from a region that had yet to become Germany.

And they have been able to do so because, at least for what were once the Grand Duchy of Baden, the Kingdom of Württemberg and the principality of Hohenzollern-Sigmaringen, they had data: both about harvests of rye, oats, barley, spelt and wheat, and about the movement of population. The climate connection was clear enough for the years around 1816 and 1846.

“Migration in the 19th century was a complex process influenced by multiple factors. Lack of economic perspectives, social pressure, population development, religious and political disputes, warfare, family ties and the promotion of emigration from different sides influenced people’s decision to leave their home country,” said Professor Glaser. “Nevertheless we see clearly that climate was a major factor.” – Climate News Network