/kloc-part of the reason why Germany immigrated to the United States in the 0 th and 9 th centuries was the climate.

1874, Germans immigrated to the United States by Hamburg ship. (? Everett historical/shutterstock) "kdsp" Today, Germany is the top immigration destination after the United States. But in the19th century, Germans fled the motherland in large numbers in order to find better overseas prospects. At that time, 500 Americans moved to North Dovander, including Donald Trump and the ancestors of the Heinz family. Now, new research shows that climate is the main factor leading to this migration pattern.

"Until today, the migration from Europe to North America is the largest in history," said rudiger Glazer, a professor of geography at the University of Freiburg. Glazer said that most literatures about German immigrants usually attribute this phenomenon to political and social problems. [Refugee crisis: Why there is no scientific resettlement]

19th century was indeed a period of great political and social turmoil in Germany, from the Napoleonic Wars to the bourgeois revolution in 1848, to the industrial revolution, and then to the establishment of the German Empire in187/kloc-0. But Glazer and his colleagues want to test the hypothesis that climate may be an important factor leading to this large-scale migration. The researchers used statistical models.

The research focuses on the area around their university, which is now Baden-Wü rttemberg in southwest Germany, where there are detailed records of immigrants, population, weather, harvest and grain prices in the19th century. This region is not Germany as we know it today; 18 15, the beginning of the research time frame, was pieced together by the Grand Duchy of Baden, the Kingdom of Wü rttemberg and the Kingdom of Prussia. )

They use complex statistical models to try to quantify the impact of climate on immigrants. Glazer said that in general, from 18 15 to 1886, about 30% of immigrants moved out of that corner of Germany, which can be explained by a series of events starting from the climate: bad weather conditions led to low crop yields, which led to an increase in grain prices, which led people to pick it up and leave in search of better opportunities. Glazer said, "There are 10 surprising ways that the weather changes history:

""that's clear. "This chain effect is convincing.

"It's not surprising when you consider that most of the population in southern Germany was rural population at that time, and household livelihood and income were closely related to agricultural productivity," said Robert McCriman, an associate professor at Wilfrid University of laurel who was not involved in the study.

Macriman said that people often associate environmental migrants with environmental refugees, or a large number of people suddenly move out of their homes due to storms, floods and a single major event. "Although this kind of event does happen periodically, we often ignore the long-term and more subtle effects of climate and environment on migration patterns," McCriman told Life Science. He added that the report shows "how climate indirectly affects immigrants by affecting the market price of goods and destroying the livelihood of families."

Glaser and his colleagues found that the surge in the number of some immigrants was related to particularly serious climate events. For example, the massive eruption of Tambora volcano in Indonesia in 18 15 sent enough volcanic ash into the atmosphere, causing global chaos. 18 16 is called "a year without summer" because farmers in the northern hemisphere experienced crop failure caused by rising food prices.

Other migration flows have more obvious geopolitical influence. The researchers found that from 1850 to 1855, the surge of immigrants occurred during the Crimean War, when France banned grain exports and squeezed the German grain market. In the meantime, Baden authorities tried to drive away poor immigrants through subsidies (partly to prevent riots).