The devastation caused to some parts of Europe during the Thirty Years War had to have an impact on population figures. But whether these were long term or not is difficult to assess. Unfortunately for historians, accurate population figures relating to the era of the Thirty Years War are difficult to come by. We do know that the following trends had occurred:
1500 to 1600: there had been a steady population increase
1600 to 1650: there was a decline in population in Germany
1650 to 1700: there was a steady recovery in the population of Germany
Rural areas suffered more than the majority of urban areas as battles were fought in rural areas. However, some urban areas did suffer very badly. The historian Langer claims that Sweden alone destroyed 2000 castles, 18,000 villages and 1500 towns in Germany. If his figures are accurate, the number of towns destroyed represented one-third of all German towns. Rural areas would have depopulated at the mere mention of approaching armies. Many armies at this time were part made up by mercenaries and their treatment of civilians and their property was legendary and feared. However, rural depopulation could be a very temporary issue as those who had fled where they lived would have returned to the area once an army or armies had moved on.
Certain cities were hit very hard by war. Probably the best example was Magdeburg. In 1618, it had a population of 25,000 with a further 35,000 in the surrounding rural area. In 1635, there were only 400 homes left standing in the city and by 1644, its population had fallen to 2,464.
If a region was lucky enough not to be on the route of an advancing army, it could escape relatively lightly. Lower Saxony's population dropped by just 10% from 1618 to 1648 whereas the population of Pomerania fell by 50%. The accepted figures are that urban areas experienced a 33% population loss while rural areas experienced a 40% loss.
A drop in population had to impact the birth rate which, in turn, would have an impact on future population figures. However, birth rate statistics can cause problems by themselves. In Augsburg, the birth rate fell by 42% but the city's population actually increased as a result of the number of people who entered the city from rural areas for the protection it offered. As with any study of population in the C17th, historians are constantly battling against figures that appear to contradict others. Such a shortage of concise data is a problem.
War, plague and famine took their toll in the Thirty Years War, but to what extent is difficult to know.
From 1634 to 1639, plague hit the whole of Germany. Areas badly affected by the plague experienced a population loss but also many who did not have the plague fled that area for their own safety and may well have returned to that region once the plague was gone. Therefore, any population dip may have been temporary. Likewise, any increase in an city's/area's population may have been temporary until people felt more confident about returning to an area that had fled from. However, if people decided to stay in the area they had fled to, this would artificially increase the population increase there. Also such trends may have occurred whether a war was being fought or not especially as plague was greatly feared.
War was also very localised in an area as large as Germany. Germany was not reduced to rubble as Langer's figures might indicate. Local conditions were important in determining population figures. Leipzig, for example, continued its trade fair throughout the duration of the war - not something one would expect if the city had been decimated by war or if the population was such that it was not worth selling to.