Iowa has changed greatly since becoming a state in 1846. The prairies that helped develop the highly productive soils have been reduced by more than 99 percent. About 95 percent of the state's prairie pothole wetlands have been drained. Over half of the original forest has been lost. These changes and other factors such as channelization of streams and rivers, soil erosion, development and urban expansion, and intensive row crop agriculture have contributed to the loss or degradation of suitable habitat for numerous plant and animal species.