The Mongols had a complex impact on the environment. These effects can be grouped into negative and positive effects. In terms of negative effects, the Mongols regularly depopulated towns and villages that they conquered throughout Europe. In other cases, they confiscated the livestock and crops. Mongols are also blamed for the spread of the bubonic plague in Europe. The plague killed about 35% of China's population and 25% of the of population in Europe. Positive effects include a century of peace from 1280 to 1360, the reopening of the silk trade routes across China and Europe, increasing cultural exchange and wealth.