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22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 GUIDE TO NEBRASKA'S WETLANDS Rainwater Basin wetlands remaining (Raines et al. 1990), and of these only 28,260 acres were naturally occurring palustrine wetlands (Smith and Higgins 1990). Using National Wetland Inventory data updated in 2011, the Rainwater Basin Joint Venture found 44,198 acres of palustrine wetlands (RWBJV 2013a); the increase is likely due to improved aerial imagery and techniques and restoration efforts. These studies indicated that palustrine, or marsh-like, emergent wetlands have decreased over the long-term, and virtually all remaining wetlands have been degraded in some fashion. Given all the various data sources, the current best estimate of wetland loss is: Of the historic average of about 204,000 wetland acres, roughly 40,000 acres, or about 17%, remain (RWBJV 2013a). Playa wetlands in the Rainwater Basin make up less than 1% of the total landscape (Bishop and Vrtiska 2008; Bishop et al. 2011). Rainwater Basin wetlands were identifi ed by the U.S. Fish and Wildlife Service as one of nine areas in the U.S. of critical concern for wetland losses (Tiner 1984). Rainwater Basin wetlands were given the highest ranking, a Priority 1, in the Nebraska Wetlands Priority Plan (Gersib 1991). The remaining wetland resources of the Rainwater Basin complex continue to face numerous threats, mostly related to conversion to cropland. Rainwater Basin wetlands face the direct threat of elimination by drainage and/or fi lling. The construction of concentration pits, also called dugouts or reuse pits, was once common, and these pits threaten the functions of wetlands by converting shallow productive water spread over a large area into a smaller, deep, and less productive water pit. Water pollution, especially culturally accelerated sediment washing into the wetlands from surrounding crop fi elds (LaGrange et al. 2011), can seriously reduce the functions of Rainwater Basins. Additionally, nearly all Rainwater Basin wetlands are threatened by changes to their watershed that divert water away from them or concentrate upland runoff water into concentration pits. Of greatest concern is the cumulative impact of these threats that cause shallow wetlands to lose a few inches of water and then no longer function as wetlands. Several invasive plant species threaten these wetlands. The spread of an aggressive cultivar of reed canary grass is a major threat. Reed canary grass forms dense, uniform stands in wetlands and provides minimal habitat for water birds. Introduced purple loosestrife and European common reed (also called Phragmites) have been found in some of the wetlands and are additional threats. A hybrid cattail, a cross of native broad-leaf cattail and introduced narrow- leaf cattail, is very aggressive and becoming a major threat. Although a native species, river bulrush can form dense stands, especially in areas with culturally accelerated sediment. Trees were not a native component of Rainwater Basin wetlands and are now About 30% of the continental population of northern pintails use the Rainwater Basin during spring migration. ETHAN FREESE, PLATTE BASIN TIMELAPSE

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