Bio E179 Lecture 1 Notes .pdf

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Biological Sciences
Rahul Warrior

Limnology and Freshwater Biology Lecture 1Wetlands1 Introduction to WetlandsWetlands have three general characteristics 1 They are wet at some point during the year 2 They have hydric soils soils formed by wateralluvial processes that are different from the soils of adjacent upland habitat Hydric soils become anoxic do not have oxygen available to plants or invertebrates when they are wet 3 They support hydrophytic vegetation vegetation that is facultatively or obligately associated with wetland conditions eg cattails bulrushes Such vascular plant species are known as wetland indicator speciesSo to delineate a wetland one must 1 test the soil to find out if it is hydric 2 identify the plants to determine if they are wetland indicator species and 3 ascertain if the site is wet at least once a year 2 The Global Pattern Loss of Wetland HabitatBefore European occupation there were over 200 million acres of wetland habitats in the United States This original resource was more than halved 54converted to other habitats or developed by 1970Only an estimated 99 million acres remained by the mid1970sCalifornia is one of the leaders in the loss of wetland habitatsStatewide 91 of our wetlands have been sacrificed 5 million acres existed in the 1780s 454000 in the 1980s and in southern California 97 of our floodplain riparian habitats are lostThe riparian forest in the Sacramento Valley is one of the bestdocumented losses with only 15 of the predevelopment gallery riparian forest surviving 800000 acres in 1850 compared to 12000 in 1972Mono Lakewater diverted for human use primarily by the Los Angeles Department of Water and Power has caused Mono to become drier and more basicMitigation by returning freshwater flow into the lake has been problematic the water column is separated into two bands differing dramatically in salinityThis is predicted to turnover within fifty years and will likely kill most of its living inhabitants notably the brine shrimp Artemia monicaAfter the turnover and mixing of the dense highly basic deep waters with the freshwater on top the lake will be recolonized by brine shrimp3 Major Causes of Wetland Habitat Loss1 Agriculture by far the greatest causenationwide roughly 87 of the loss was due to agriculture 2 Urban development historically it is estimated that 8of the loss was due to urban development 3 Other Development eg dams stream diversion and so forth5was due to these other developmentsDams regulation of water flows and diversions also cause loss of wetlands and this is a worldwide problemDams and other humancaused hydrologic alterations strongly to moderately affect 77 of 139 largest river systems in the United States Europe and the former Soviet UnionThis is due to dams and water regulation resulting from reservoir operation interbasin diversion and irrigation The remainders are small and are in the far north away from human settlementsIn hydroelectric plantsdams water levels can drop or be raised rapidly dictated by human demand for electricity resulting in letting more or less water out of the dam to generate power causing further risk to both habitat and human health Tiner et al after ZinnCopeland 1982 and Gosseknik and Baumann 1980 describe numerous humaninduced threats to wetlandsDirect threatsDrainage for crop production timber production and mosquito controlDredging and stream channelization for navigation channels flood protection coastal housing development and reservoir maintenanceFilling with dredged spoil and other solid waste disposal roads and highways and commercial residential and industrial development
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