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involved in research projects seeking to find improved ways of restoring natural 

 wetland functions and values. 



During the last century, approximately 4,500 non-native species of plants and ani- 

 nrials have been introduced to the U.S. This invasion of species has created competi- 

 tion with native organisms that can be problematic and costly to control. The U.S. 

 Fish and Wildlife Service annually spends hundreds of thousands of scarce operat- 

 ing dollars attempting to control exotic wetland plants within the National Wildlife 

 Refuge System. For example, control of purple loosestrife (Lythrum alicaria) in wet- 

 lands of the Upper Midwest and carp {Cyprinus carpio) within floodplain wetlands 

 of the Mississippi Valley has become an annual battle for State and Federal biolo- 

 gists. In some States, particularly Hawaii, non-native plants and animals pose 

 threats to endangered indigenous species. In addition, the U.S. Office of Technology 

 Assessment has released a report suggesting that non-native species may cause as 

 much as $97 million in damages to U.S. agriculture. 



Purple Loosestrife 



Purple loosestrife is an aggressive, exotic perennial that displaces many natural 

 wetland plants and degrades wetland functions and values throughout the temper- 

 ate region of North America. The spread of this species has been enhanced by the 

 absence of natural enemies and disturbance of wetland systems by humans. The 

 plant now occurs in dense stands throughout the northeastern U.S., the Midwest, 

 and in scattered locations in the western U.S. and Canada. Newly created irrigation 

 systems in many western States have facilitated further establishment and spread 

 of purple loosestrife. 



The competitive advantage of purple loosestrife over other wetland plants is high- 

 lighted by such attributes as high annual seed production (greater than 2M seeds/ 

 mature plant), good seed viability (almost 100 percent germination; 80 percent after 

 2-3 years submergence), high seedling densities (10,000-20,000/sq. meter) and rapid 

 growth (1 cm/day). Mature plants often have 30 or more shoots arising from the 

 rootstock. These can reach 6-7 feet in height, forming dense canopies which severely 

 restrict the amount of light available to plants beneath. Such stands also offer little 

 in the way of food or cover for most forms of wetland wildlife including waterfowl. 



The negative impacts on aquatic ecosystems caused by invasions of purple 

 loosestrife far outweigh any of its attributes. The species forms large monotypic 

 stands that reduce the biotic diversity of wetland systems by replacing diverse, pro- 

 ductive emergent and submergent plant communities with a single species. Invasion 

 of wetlands by loosestrife negatively impacts fish spawning sites, nutrient cycling, 

 and invertebrate productivity and drastically reduces vertebrate species use. 



Strategies for controlling purple loosestrife have included physical removal of 

 plants, mowing, burning, water level manipulation, and the use of plant competitors 

 and chemicals. None have proven effective over a broad range of conditions. Addi- 

 tionally, each methodology is costly and requires continuous treatment. Recently, bi- 

 ological controls using natural "enemies" (insects, pathogens, etc.) of purple 

 loosestrife have shown promise. Such biological control offers the greatest potential 

 as a long-term, safe, economical, and effective control technique and should be sup- 

 ported. 



Common Carp 



After initial introduction in the late 1800s, common carp are now a wide spread 

 exotic pest in aquatic ecosystems across North America. Tney are most common in 

 the Mississippi and Missouri River systems and have expanded northward to 60 de- 

 gree July isotherm. 



The profound impact carp have had on the ecological productivity and diversity 

 of riverine, lacustrine, and palystrine wetland systems is well documented. Over- 

 abundant populations of carp can consume large quantities of submerged aquatic 

 wetland plants, thereby directly affecting both plant and waterfowl productivity. In 

 addition, the characteristic bottom feeding habits of carp increases turbidity of wa- 

 ters and disturbs and impacts aquatic plant growth and reproduction. 



Control of carp has taxed the ingenuity and finances of conservation agencies for 

 more than 80 years. Increasing restrictions in the use of piscicides and other similar 

 piscicultural techniques have reduced the ability of fish and wildlife managers to 

 address carp infestation problems. In many instances, the only management option 

 to restoring functioning wetlands is to completely impound wetlands and, through 

 water-level manipulations, exclude carp from them. 



In response to the 1993 flood, recent planning efforts by the U.S. Fish and Wild- 

 life Service for National Wildlife Refuges along major rivers in the Midwest calls 

 for eliminating impoundments or reducing impoundment management for wildlife 

 on refuge lands. This action would reduce biological diversity of the refuge system 



