Byambasurem Oyunsanaa, Columbia University (image) The Earth Institute at Columbia University Share Print E-Mail Caption More rainfall means more grass, which would mean more war horses for Mongol cavalry. Ecologist Byambasurem Oyunsanaa plots plant abundance on the modern steppe. Credit Kevin Krajick/Earth Institute, Columbia University Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.