Restoration = return of a wetland from a disturbed or altered condition caused by human activity to a previously existing condition

Transcription

1 Wetland Ecology Lectures Creation & Restoration Two general starting points Learn & understand wetland science & its principle first Broaden your horizons beyond the field you were trained in so that you resist the ever-present temptation to over-engineer, over-botanize, or over zoologize the wetlands that you create or restore Definitions Restoration = return of a wetland from a disturbed or altered condition caused by human activity to a previously existing condition Creation = the conversion of a persistent upland or shallow water area into a wetland by human activity Constructed wetland = a wetland that has been developed for the primary purpose of containment or pollution removal from wastewater or runoff Mitigating Habitat Loss Requires wetlands to be created, restored, or enhanced to replace those lost in developments Highway construction Coastal drainage Filling Commercial development Mitigate means to make less harsh or harmful (poor use of language here!) We should say mitigating the loss of a wetland!!!!! Or call them replacement wetlands Legal success = compares the lost wetland function & area with that which is gained in the replacement wetland Ecological success = compares the replacement wetland with a reference wetland Overall success = legal + ecological USACE no net loss implementation appear to be working Permitted = loss Mitigated = gain Two reasons to not get excited about net gain of wetlands 1. impossible to tell from general numbers how successful this trading has been

2 Think of the functions lost!!!!! 2. the estimated gain of 115,000 ha over 13 years does not impact the 47,000,000 ha of wetlands that occurred from pre-settlement time 1980 in the U.S. National distribution Tennessee mitigation banks Agriculture Land Restoration Farm pond creation ~ 50,000 ponds/yr Marshes develop around perimeter, while others have been converted to marshes Many non-agriculture ponds are built in housing & commercial developments Conservation Reserve Program (CRP) & Wetland Reserve Program (WRP) have led to increased wetland area CRP (1997) increase emphasis to the enrollment & restoration of cropped wetlands Wetlands that produce crops but serve wetland functions when crops are not being grown Voluntary contracts are in place (10 15 years) In exchange, participants receive annual rental payments & payment up to 50% of the cost of establishing conservation practices WRP (1990) offers landowners opportunities to protect, restore, & enhance wetlands on their property Provides substantial funds for farmers to do so Includes permanent easements, 30 yr easements, or 10 yr restoration cost-share agreements As of 2004 ~ 660,000 ha of wetlands & adjacent uplands have been enrolled in the WRP Most intense activity in Lower Mississippi River basin and in Florida Most areas are flood-prone & ~ 70 ha in size Forested Wetland Restoration Much less experience in restoring/creating forested systems compared to marshes Forest regeneration takes decades rather than years Much focus has been on lower Mississippi River alluvial valley 78,000 ha were reforested by federal agencies in a 10 yr period Small contribution to the 7,200,000 ha already lost Hydrologic & Water Quality Restoration with Wetlands Why are wetlands created or restored?

3 Primarily for both habitat & water quality values One of the largest wetland restorations is being carried out in the Florida Everglades Kissimmee Okeechobee Everglades region in the southern third of Florida Case Studies in book Page Using Wetlands to Prevent Hypoxia DO < 2mg/L now extends over an area of million ha Nitrogen (nitrate) most probable cause 80% is from the 3 million km 2 M.R.B Peatland Restoration Potentially the most difficult to restore When mines are abandoned w/o restoration, the area rarely undergoes secondary succession to original moss-dominated system Coastal Wetland Restoration Salt Marshes Early pioneering work done in Europe In U.S. on NC coastline, Chesapeake Bay, & Florida coastlines Primary plant choice in U.S. is Spartina alterniflora Same spp is a noxious invasive on west coast Marsh grasses tend to distribute easily through seed dispersal quite rapid once reintroduction has occurred Successful coastal wetland creation Sediment elevation is most critical factor determining successful establishment of vegetation. Site must be intertidal In general, upper ½ of the intertidal zone is more rapidly vegetated than lower elevations Sediment composition does not seem to be critical factor in colonization by plants unless the deposits are almost pure sand Subject to rapid desiccation at upper elevations The site needs to be protected from high wave energy Vegetation does not establish at high-energy sites Most sites will revegetate naturally from seeds from higher elevations

4 Good stands can be established during 1 st season of growth, although sediment stabilization does not occur until after two seasons Mangrove restoration is similar to salt marsh restoration Shrimp farms (sold very cheap!!) are built on destroyed mangrove forests Shrimp ponds only last 5-6 yrs before they develop toxic levels of sulfur then abandoned more mangroves destroyed Mangrove restoration often involves physical planting of trees Restoring mangroves Get the hydrology right Do not build a nursery, but grow mangroves & plant only areas totally devoid of mangroves See if conditions that prevent natural colonization can be corrected; if not, pick another site Examine normal hydrology in reference mangrove swamps as your model for restored sites Remember that mangrove swamps do not have flat floors, they have subtle topographic patterns Tidal creeks to facilitate flooding & drainage of tide waters Evaluate the cost of restoration early in the project design to make the project cost-effective Original Design Revised Plan Delta restoration Two main ecological resource goals Protect & restore the functioning of the deltaic ecosystems in the context of a geologically dynamic framework Controlling pollution from entering the downstream lakes, oceans, gulfs, & bays Louisiana Delta Restoration CWPPRA in 1990 Congress of the Coastal Wetland Planning, Protection & Restoration Act Remember plan 2050 This diversion structure adds 1,100 km 2 area of fresh, brackish, & saline wetlands General Principles of Restoration 1. Design the system for minimum maintenance 2. Design a system that utilizes natural energies (streams) 3. Design system with hydrologic, ecological landscape, & climate in mind 4. Design system to fulfill multiple goals

5 1 major objective & several secondary obj s 5. Give system time 6. Design for function, not form 7. Do not overengineer design No rectangular basins, rigid structures & channels, & regular morphology Ecological Principles for Consideration 1. Landscape context & position 2. Natural habitat types 3. Specific hydrologic regime 4. Ecosystem attributes develop differently 5. Nutrient supply rates affect biodiversity 6. Specific disturbance regimes increase spp richness 7. Lack of seed bank limit spp recovery 8.must consider life-history traits 9. must consider succession theory 10. genotypes influence ecosystem structure & function Defining Goals Wetland placement is crucial Site selection 1. restoration more feasible than creation 2. surrounding land use & future plans 3. detail hydrology of the site 4. find site where natural inundation is freq 5. characterize soils 6. chemistry of soils, gw, for water quality 7. evaluate seed banks 8. assess availability of fill material 9. ownership of land 10. determine corridors 11. assess site access

6 12. ensure adequate amount of land is available to meet obj s Creating & Maintaining Hydrology 1. Drop pipes 2. Flashboard risers 3. Full-round riser (combo of two) Soils Better to develop wetlands on hydric soils. Provides 3 advantages: Vegetation Hydric soils indicate the site may still have or can be restored to appropriate hydrology Hydric soils may be a seedbank of wetland plants still established in the soil Hydric soil may have the appropriate soil chemistry for enhancing certain wetland processes Freshwater marshes Bulrush (Scirpus spp) Cattails (Typha spp) Sedges (Carex spp) Water lilies (Nymphaea spp.) Spatterdock (Nuphas spp.) Coastal Marshes Spartina alterniflora in southeast S. townsendii & S. anglica in China & Eurpoe Forested Wetlands Nutall oak (Quercus nuttallii) Cherrybark oak (Quercus falcata var. pagodifolia) Willow oak (Quercus phellos) Water oak (Quercus nigra) Cottonwood (Populus deltoides) Sycamore (Platanus occidentalis) Green ash (Fraxinus pennsylvaninca) Sweetgum (Liquidambar styraciflua) Pecan (Carya illionensis)

7 Estimating Success Spotty record of successes is believed to be due to: Little understanding of wetland function by those constructing wetlands Insufficient time for wetlands to develop A lack of recognition or underestimation of the self-design capacity of nature Summary of Principles 1. Restoration + Creation must be viewed with care 2. Multidisciplinary expertise in planning 3. Clear, site-specific measurable goals 4. Detailed plan concerning all phases of the project prepared in advance 5. Site-specific studies should be carried out in the original system 6. Careful attention to hydrology needed 7. Design to be self-sustaining systems 8. Should consider relationships of the wetland to watersheds, water sources, other wetlands & adjacent uplands & deepwater habitats 9. Buffers, barriers & other protective measures often needed 10. Restoration should be favored over creation 11. Monitoring & midcourse corrections is needed 12. Long-term management is needed in some systems 13. Risks should be reflected in standards & criteria for project design 14. Special treatment for restoration of artificial or altered systems 15. ADVANCED, CAREFUL PLANNING