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Restoration of a Sonoran Desert spring ecosystem and vertebrate assemblage in an urban setting.
ROSEN, PHILIP*,1, FONSECA, JULIA2, 1 UNIVERSITY OF ARIZONA, TUCSON, AZ., firstname.lastname@example.org PIMA COUNTY FLOOD CONTROL DISTRICT, TUCSON, AZ.
ABSTRACT- Native aquatic vertebrates are highly threatened in the American Southwest, and their restoration may be complicated. The Tucson, Arizona, region lies in Gila River Basin headwaters. Its natural waters still support many native vertebrates, although key valley bottom streams and wetlands have been eliminated. As elsewhere in the Southwest, invasive, introduced species are a widespread problem. However, regional headwaters are relatively less desiccated, modified, or inundated by invasive species. Throughout Gila River Basin, 20th century impoundments (ponds and lakes), which replaced and eliminated natural springs and streams, are key habitat modifications favoring non-native species. A logical beginning for aquatic ecosystem restoration is in smaller, more tractable headwaters. We describe plans for Agua Caliente Spring, a large desert spring near the Tucson Basin headwaters. The historic warm spring rises on a gentle slope, 0.9 km from a major arroyo. Although highly modified, and heavily dominated by non-native vertebrates, it is currently a natural resource park, and is being considered for restoration by a public coalition. There is potential to create habitat for up to 11 native species (8 fish, 1 frog, and 2 reptiles), 7 of which suffered massive 20th century declines. Terrestrial riparian habitat would also be restored and diversified. Although non-native fish can be readily removed, a complicating factor is regional presence of bullfrogs, which can move overland to colonize ponds, where they proliferate and foreclose restoration of herpetofaunal elements. We propose to create flowing, cienega-like habitat not utilized by bullfrogs, but suitable for native species. We also propose to release water to create an in-channel arroyo stream, where natural flash-flooding will favor native species. The project takes a novel approach of bringing endangered species conservation into a metropolitan area, and into direct contact with the public. Our design incorporates efficient means for re-removals of non-natives, supplementary to educational efforts. As part of Pima County's Sonoran Desert Conservation Plan, it represents a prototype and exemplar for use of other urban waters and riparian areas, by integrating recreation and biodiversity planning.
KEY WORDS: restoration, urban ecology, native fish, herpetofauna