Rachael+Thames

There are approximately 2.5 million dams in the United States of America. This statistic shows the degree to which the human race will alter natural areas in favor of possible economic benefit, no matter how short lived it may be. Currently, though, dams all over the country are being modified or removed, whether for the benefit of the ecosystem or the public. Proponents for or against dam removal have many scientific sources to assist them in arguing for their specific view and the possible benefits that may be obtained for the public as well as for the ecosystem. Values are the deciding factor, though, and people with different values may still seek the same outcome. Whether values are for increased recreational opportunities or increased revenue from those opportunities the end result may be the same even though the starting points are completely different.

Picture of the Chesaning Dam Removal Project: Before and After
 * [[image:http://recovery.doi.gov/press/wp-content/uploads/2009/09/chesaning_09-21-09_before.jpg width="900" height="192" caption="chesaning_09-21-09_before"]]



Dam Removal** There are several reasons to support dam removal regarding benefits to ecosystems and the public. Ecosystem components ranging from biota to habitat can benefit from the removal of dams and directly or indirectly affect the public in a beneficial manor. In the past many dams were errected in the name of flood control. Yet, the very floods that were being controlled were depositing rich nutrients to the floodplains in which high amounts of plant production helped to increase biodiversty levels and in which agricultural producers now raise crops. Crops continuously grown in these floodplain areas are not getting the annual increases in nutrients that were brought about by these floods. Removal of dams can bring these naturally occuring fertilization measures back, and in turn can reduce the costs of fertilization to the agricultural producers who utilize these areas. Such flood increases can also increase sedimentation and nutrient level deposition in areas not used for agriculture and can lead to higher amounts of emergent vegetation wetlands which help to store flood waters and slowly release them so as to decrease the flashiness of floods. These emergent vegetation wetlands also become habitat and forage for aquatic and wildlife species. By removing a dam nutrient and sediment transfer levels can be increased leading to benefits for both agriculture and ecosystems.

There are several reasons to support dam retention which will maxamize benefits and reduce costs to the public and the ecosystems. Large dams prevent the spread of several invasive species such as the sea lamprey and rusty crayfish. Invasive species can affect the population numbers and species composition of native species in aquatic ecosystems. By funding the maintenance costs of larger barriers over chemical control of certain invasive species, the negative effects of chemicals on public health as well as non-target species can be greatly reduced.
 * Dam Retention**

__Images__ Department of the Interior Recovery Investments, alpena National Fish and Wildlife Conservation Office []

__References__ Dr. Dan Hayes, Stream Restoration via Dam Removal lecture

Great Lakes Fisheries Commission, Lampricides and Facts about Stream Treatments []