Watching Landscapes Change (image) University of Arizona Caption Repeat photography is one of the tools range ecologists use to document how lands change: In 1902, photographer David Griffiths' horse-drawn buggy was clearly visible in the open grassland, surrounded by scattered desert hackberry plants at the foot of Huérfano Butte, south of Tucson, Ariz. By 1941, an unknown photographer documented burro weed and cholla cactus popping up, along with velvet mesquite trees. In 2007, the grass cover had given way to velvet mesquite trees, and prickly pear have replaced cholla as the dominant cacti. Credit Mitchel McClaran/University of Arizona Usage Restrictions This visual may only be used in conjunction with reporting/posting of this news release. Image/video credit must be included exactly as indicated. 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.