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The Scientific Basis for Protecting Wetland Buffers

The Scientific Basis for Protecting Wetland Buffers. Robert Buchsbaum Massachusetts Audubon Society. Scott Jackson University of Massachusetts. Wetland Functions Affected by Buffers. Pollution prevention Surface Groundwater Storm damage prevention Fish and shellfish habitat

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The Scientific Basis for Protecting Wetland Buffers

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  1. The Scientific Basis for Protecting Wetland Buffers Robert Buchsbaum Massachusetts Audubon Society Scott Jackson University of Massachusetts

  2. Wetland Functions Affected by Buffers • Pollution prevention • Surface • Groundwater • Storm damage prevention • Fish and shellfish habitat • Wildlife habitat • Aesthetic and scenic values

  3. Selected Definitions of Vegetated Buffers • Transitional area between two different land uses where one mitigates the impact from the other. • Zones of undeveloped vegetated land along a water body that trap pollutants. • Riparian zone: The interface between terrestrial and aquatic ecosystems. Encompasses sharp gradients From Desbonnet et al. 1994 and Gregory et al. 1991

  4. Buffers are particularly important for protecting Critical Areas • Drinking water supplies • ACEC’s • Wildlife refuges • Rare plant/ animal habitats • Regionally significant ecological communities • Shellfish beds

  5. Pollution Prevention

  6. Types of pollutants affected by buffers • Particulates • Total suspended solids (TSS) and sediments • Toxic organics and metals associated with particles • Pathogens: bacteria and viruses • Soluble • Nitrogen • Phosphorus

  7. Characteristics of buffers that affect pollution attenuation capacity • Slope • Width • Soil characteristics • Surface “roughness” (to slow down flow) • e.g., vegetation cover • Surface hydrology • Channelization v sheet flow • Fracturing of underlying rocks

  8. Landscape factors • Relative size of wetland, buffer, and surrounding watershed • Position of wetland within watershed

  9. Possible groundwater flow paths: 1

  10. Possible groundwater flow paths: 2

  11. Lots of variation in the relationship of pollution attenuation to buffer widths From Wenger 1999

  12. Effects of soils and drainage are obvious From Wenger 1999

  13. Effect of slope From Wenger 1999

  14. Relationships of buffer widths to pollutants Sediments From Desbonnet et al. 1994

  15. Total Suspended Solids From Desbonnet et al. 1994

  16. Interaction of Width and Slope From Wenger 1999

  17. Total Nitrogen From Desbonnet et al. 1994

  18. Nitrate Denitrification is the key process in nitrate removal From Desbonnet et al. 1994

  19. Phosphorus From Desbonnet et al. 1994

  20. Modeled removal of Sediments and TSS From Desbonnet et al. 1994

  21. Modeled Removal of Nutrients From Desbonnet et al. 1994

  22. Fecal Coliforms • Bacteria behave somewhat like particles with a limited lifespan outside a warm-blooded intestine • Buffers “buy time”, allowing bacteria to die off naturally before reaching a sensitive area.

  23. Die-off rates of fecal coliforms • Typically 90% die off at ca. 48 hrs in freshwater • Typically 90% die off at ca. 1 day or less in salt water • But lots of variation depending on type of bacteria and characteristics of the sediment • Survival times of over a month and travel distances greater than 2000 feet have been recorded.

  24. Freshwater die-off rates of coliform bacteria From Mitchell and Chamberlain, 1978

  25. Relationship of housing density within 100 foot buffer to fecal coliform concentrations Data from Bochman 1990 (Cape Ann salt marsh creeks)

  26. General Conclusions: Buffers and Water Quality • On average, a 100 foot buffer will remove in the neighborhood of 70% of the pollutants • A small buffer (e.g., 25 feet) is still very worthwhile – removes over 50% of pollutants • Going from 300 to 600 feet gives you only an additional 10% of pollutant removal • Scientifically, nothing is better than site-specific information.

  27. Wildlife Habitat Function of Buffers • Ecological link to both wetlands and upland • Nesting sites for wetland animals • Hibernation sites for wetland animals • Refuge during times of very high water • Migration corridor • Shade for cold water fish

  28. Wildlife Habitat Functions (2) • Ameliorates the effects of disturbance • Improves water quality • Provides a buffer from invasive and generalist animals • Woody debris from buffer provides a habitat for wetlands invertebrates • Provides an energy source to invertebrates in the form of detritus • A habitat for “buffer specialists”

  29. New England Animals likely to be sensitive to activities within wetland buffers • Waterfowl – particularly during nesting • Herons and egrets – feeding and nesting • Shorebirds – during migration • Semiaquatic mammals – e.g., mink, otter • Semiaquatic reptiles – e.g. turtles • Vernal pool-breeding amphibians • Cold water fish – e.g., trout • Fish spawning in clear running water – e.g., smelt • Buffer species, e.g., yellowthroat

  30. Shade regulates water temperature

  31. Buffer supplies woody debris to the stream

  32. Freshwater Wetland-Dependent Wildlife with Upland Requirements (MA) Boyd, 2001: Report available at: http://www.umass.edu/umext/nrec/pages/biodiver_resrc.html

  33. A number of birds do best where wetlands are interspersed with forests

  34. ( X ( X ( X ( X ( X ( X ( X ( X ( ( X X ( X ( X ( ( X X ( X ( X ( ( X X ( X ( X ( ( X X ( X ( X ( X ( X ( X ( X ( ( X X ( X ( X ( X ( X ( X ( X ( X ( X ( ( X X ( X ( X ( X ( X ( ( ( ( X X X X ( X ( ( ( ( X X X X ( ( ( ( ( X X X X X ( X ( ( X X ( ( ( X ( X X X 0 . 6 0 0 6 K o e r N Blanding’s Turtle Home Range W E S ( X ( X ( X ( X ( ( X X ( X ( X ( ( ( X X X ( X ( ( X X ( ( X X ( X ( X ( X M a l e # 3 0 6 H o m e R a n g e S c a l e 1 : 1 2 , 0 0 0 2 2 0 0 0 0 1 1 2 0 0 2 L o c a t i o n s L o c a t i o n s ( X ( X M o v e m e n t s M o v e m e n t s 5 0 % K e r n e l 5 0 % K e r n e l 9 5 % K e r n e l 9 5 % K e r n e l . i l m t e s

  35. VernalPool Setbacks d=? d

  36. VernalPool Setbacks d' d Appropriate Habitat

  37. VernalPool Setbacks d' d Adult Upland Habitat use

  38. VernalPool Setbacks d' juveniles d Adults

  39. Differences in bird numbers in a relatively developed v undeveloped salt marsh creek R. Buchsbaum unpublished data, Essex Bay, MA

  40. Buffer vs pannes as an explanation for wader density of different marsh sites

  41. Buffers help protect against invasive species Mark Bertness and coworkers have shown an association between Phragmites australis at the upper edges of salt marshes and houses along the upland edge. Bertness, M.D., P. Ewanchuck, and B.R. Silliman. 2002. Anthropogenic modification of New England salt marsh landscapes. Proceedings of the National Academy of Science. 99: 1395-1398

  42. Roads reduce wildlife habitat value A study in a forested area of Ontario showed: • bird diversity lower within 1 km of roads • plant diversity lower within 1-2 km of roads • herp and mammal diversity lower within 2 km of roads • 1-2 km buffer from road needed to maintain maximum diversity Findlay, C.S. and J. Houlahan. 1997. Anthropogenic correlates of species richness in southeastern Ontario wetlands. Conservation Biology 11:1000-1009

  43. Buffers from Disturbance • Great Blue Herons – 300 feet • Great Egret – 60 feet • Black Duck – 240 feet for nesting • Bald Eagle – 1500 feet • Various shorebirds – 180-300 feet • Muskrat – 33 feet • Mink – 330 feet

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