These values can be considered from the perspective of three hierarchical levels:

Transcription

1 Wetland Ecology Lectures Wetland Values Wetland Values These values can be considered from the perspective of three hierarchical levels: Population Ecosystem Global Populations easiest value to identify Animals Harvested for pelts Muskrats (Ondatra zibethicus) - 10 million pelts harvested/yr. Found throughout U.S. 50% comes from Midwest; 25% northern Gulf Nutria (Myocastor coypus) 2 nd most abundant species. 97% comes from Louisiana Others in less abundance are raccoons, mink, beaver, otter, and alligator Waterfowl & Other Birds 80% of America s breeding bird populations & 50% of the 800 species of protected migratory birds rely on wetlands $58 million to local economies (# for Mississippi Flyway alone) Highly evident in Prairie-Pothole region Loss is ½ of original wetlands average of 22 million waterfowl Population trends coupled with wet/dry seasons From dry wet periods duck populations increased by 60% Fish & Shellfish > 95% of fish & shellfish harvested commercially in U.S. are wetland dependent 1.9 billion to U.S. GNP Many breed or lay eggs in coastal or freshwater wetlands during the spring high water events # of wetlands shows direct correlation with wetland area

2 For certain species the recreational catch outweighs the commercial catch Timber & Vegetation Harvest 22 million ha of wetland timber in U.S. 2/3 of this area east of Rocky Mountains Mississippi Alluvial Valley and forests of the southeast mostly deciduous Forests of the northern tier are mostly evergreen 13 million ha of bottomland hardwood & cypress swamps ~ 112 m 3 of merchantable timber/ha. $620/ha. (or $8 billion total) Water hyacinth (Eichhornia crassipes) can produce Btu of methane/yr and remove all nitrogen from wastewater of a city of 700,000 Endangered & Threatened Species Wetlands are necessary for the survival of a disproportionately high % of endangered & threatened species Only occupy 3.5% of land area Of 209 endangered species (1986) 50% depend on wetlands for survival 1/3 rd of N.A. fish are threatened, endangered, or of special concern 63 species of plants & 34 species of animals are listed & occupy southern U.S. wetlands (Ernst & Brown 1989) In Florida, 18% of amphibians & 35% of all reptiles are considered threatened or endangered Or status unknown Whooping Cranes nest in wetlands (Canada) during spring & summer In fall they migrate to Texas American alligator was declared endangered in 1970 s Now flourishing Gator holes can contribute to ecosystem health Material excavated supports trees Provides cover for insects, birds, turtles, snakes In turn, top-predators attracted to these areas Slackwater darter (Etheostoma boschungi) Small fish found in creeks in TN & AL Migrates 1 5km upstream to spawn

3 Deposits eggs only on one species of rush Ecosystem Values Major values to the public for: Flood mitigation Storm abatement Aquifer recharge Water quality improvement Aesthetics General subsistence Flood mitigation Wetlands influence regional flow regimes Intercept & store storm waters Changes stormwater peak discharges Size of wetland mitigates this USACE study (1972) showed that if 3,400 ha of the Charles River basin were drained & leveed off from the river, flood damages would increase by $17 million per year Flood Season Dry Season Mississippi River BHF s stored floodwater equivalent to 60 days of river discharge Storm Abatement Coastal wetlands absorb the first fury of a tropical storm Aquifer Recharge This phenomenon is not well documented When recharge does not occur it is because: Most wetland soils are impermeable Most studies agree that small wetlands contribute more to recharge than do large wetland systems Improved Water Quality Wetlands have several attributes that influence the chemicals that flow through them, whether natural or anthropogenic Reduction in water velocity causing sediments & chemicals sorbed to sediment to drop out of the water column

4 Anaerobic & aerobic processes in close proximity, promoting denitrification, chemical precipitation, & other chemical reactions that remove certain chemicals from water High rates of productivity in many wetlands that can lead to high rates of mineral uptake by vegetation & subsequent burial in sediments when plants die Diversity of decomposers & decomposition processes in wetland sediments Large contact surface of water with sediments because of the shallow water, leading to significant sediment water exchange Accumulation of organic peat in many wetlands cause permanent burial of chemicals Aesthetics A difficult aspect of a wetland to capture is aesthetic value Nonconsumptive use Values Simply put, people like being in wetlands Excellent biological laboratories Hunting & fishing Cultural heritage Subsistence Use Wetlands provide primary sources on which many village economies are based Societies have adapted to local ecosystems over many generations Few alternative lifestyles exist for these cultures Regional & Global Values Although wetlands maintain water quality, the influence in much more broad in scale Significant roles in nitrogen, sulfur, methane, & carbon dioxide Nitrogen Wetlands are important in returning excess nitrogen to the atmosphere through denitrification Requires the proximity of an aerobic & reducing environment (surface of a marsh) Anthropogenic inputs of nitrogen flow into wetlands (ideal for denitrification) thus, important to world s nitrogen balance Wetlands provide a solution to eutrophication Sulfur Atmospheric load of sulfur greatly increased due to fossil fuel burning Natural biogenic processes = fossil fuel burning (103 x vs. 104 x g/yr, respectively) Salt marshes account for 25%

5 Sulfates are washed out by acid rain, acidifying oligotrophic lakes & streams Carbon Cycle Burning fossils fuels & clear-cutting forests adds CO2 to atmosphere Huge volume of peat serves as sink for carbon globally If disturbed, could contribute significantly to global CO2 concentrations 1,400 Pg C is stored globally 1/3 to ½ is stored in wetlands Methane release is 20x more effects as a greenhouse gas 0.04 to 0.10 Pg C/yr from rice paddies alone Wetlands could potentially shift from sink to a source of carbon to the atmosphere Quantifying these values Ecological valuation is primarily based on wildlife habitats. E.P. Odum described the following procedure: Make list of all values that a knowledgeable person can apply to the situation and assign a value of 1 to each Scale each factor in terms of maximum level If 200 ducks/acre could be supported by a first-class marsh but only 100 are supported by marsh in question, then the scaled factor is 0.5 or 50% of the maximum value for that item Weigh each scaled factor in proportion to its relative importance; If value 2 is considered 10 times more important to the region than the value 1, then multiply the scale value of 2 by 10 Add the scaled & weighted values to obtain a value index Habitat evaluation procedures Wetland Evaluation Techniques Social significance: Assesses the value of a wetland to society in terms of its economic value, strategic location, or any special designations it carries Effectiveness: Site s capacity to carry out a function because of its physical, chemical, or biological characteristics Opportunity: Refers to the opportunity of a wetland to perform a function to its level of capability Hydrogeomorphic Analysis Group wetlands into HGM classes with shared properties

6 Define the relationship between HGM properties & functions of wetlands Develop functional profiles for each wetland class Develop a scale for expressing functions within each wetland class Develop the assessment methodology itself