It also completely destroyed Russian culture for example and set them back hundreds of years[1]. Payments to Mongols continued up until almost 1500.
[1] http://en.wikipedia.org/wiki/Mongol_invasion_of_Rus%27#Impac...
[1] http://en.wikipedia.org/wiki/Mongol_invasion_of_Rus%27#Impac...
It has been argued[by whom?] that without the Mongol destruction of Kievan Rus', the Tsardom of Russia and subsequently the Russian Empire would not have risen. Trade routes with the East came through the Rus' lands, making them a center for trade from both worlds. Mongol influence, while destructive to their enemies, had a significant long term effect on the rise of modern Russia, Ukraine, and Belarus.
— http://en.wikipedia.org/wiki/Mongol_invasion_of_Rus%27#Impac...
That's is entirely consistent both with it decimating the earlier civilisation across a smaller region centered on Kiev, and with it having a negative impact on economic and cultural growth in that region and surrounding regions which was felt centuries afterward. Especially if you consider Tsarist rule that Mongol invasions arguably paved the way for to be amongst the factors responsible for the relative backwardness of the Russian Empire.
They established fair law for 80 years at most, and at the price of killing off a substantial percentage of the peasantry (who the Mongols, as pastoralists, viewed individually as less valuable than a horse) of conquered regions. In Iran, the depopulation led to the underground irrigation system, known as the qanats, falling into disrepair, which led to formerly productive agricultural lands drying up, and the region regressing from agriculture to pastoralism. In the absence of a productive countryside, some of the largest cities never recovered until the 20th century.