Scientists have begun to account for the topsy-turvy carbon cycle of the Colorado River delta – once a massive green estuary of grassland, marshes and cottonwood, now desiccated dead land.“We’ve done a lot in the United States to alter water systems, to dam them. The river irrigates our crops and makes energy. What we really don’t understand is how our poor water management is affecting other natural systems – in this case, carbon cycling,” said Cornell’s Jansen Smith, a doctoral candidate in earth and atmospheric sciences.