Students from the Gilbert Unified School District's Mesquite High School honors biology and ecology classes, along with volunteers from the Sierra Club, spent Sept. 17 cleaning up Rio Salado Park in downtown Phoenix. For three hours they removed tamarisk and buffelgrass, two invasive species that rob native plants of the water needed for survival. The repurposed park was once a dump. More than 200 migratory birds, along with migrating monarch butterflies, visit the park each year.