SPRINGS ECOLOGY OF THE SOUTHERN COLORADO PLATEAU

Springs are among the most biologically productive, diverse, and threatened systems on Earth, yet little attention has been devoted to understanding their ecology or conservation status. We describe the ecological characteristics of more than 300 springs on and adjacent to the southern Colorado Plateau. Springs from 0-1800 meters elevation commonly have 100- to 1000-fold higher productivity than the adjacent uplands, a pattern that is strongly nonlinear in its relationship with elevation. Plant and invertebrate diversity is commonly 2- to 10-fold higher and species density is 100- to 600-fold higher at springs, for these taxa. For example, more than 60 percent of the region’s more than 80 aquatic beetle species occur only in springs or springfed streams. Landsnail, butterfly and bird diversity is commonly dramatically greater at springs. Rates of plant and landsnail endemism are also high at springs, particularly in paleorefugia. Vertebrates are not spring obligates, but springs are important water sources and habitat for them. For example, in one large surveyed region where the combined area of springs made up .002% of the total area, we found 1/3 of the region’s birds using spring habitats.

More than 90 percent of springs in low relief terrain have been modified by human activities, but additional inventory is needed in high relief terrain. Some species are restricted to certain geomorphic habitats at springs and are heavily impacted when these habitats are degraded. In some cases, springs we visited were so highly impacted that it was impossible to tell what vegetation existed there naturally. Grand Canyon National Park's protected springs give us clues to the former distribution of plants at springs on the Plateau. To assist managers in recovering these areas, we will use our vegetation and hydrologic data to generate a predictive model of spring vegetation. During our surveys we found many new species records for northern Arizona in particular, and some new records for the State of Arizona. Many species are more restricted in range than they were in the Pleistocene climate 10,000 years ago, and because of this, springs are essential to their continued survival. A national initiative to inventory, assess, and conserve springs ecosystems is needed.