96 



Because wetland functions are controlled by physical, chemical and biologicaJ processes, wecland 

 functions are strongly related to complexity, pristiness (" diversity), sire and location of the wetland as 

 follows: 



CPmple>t't> Pristine Sag LflSfllicD 



Life Support High High High Mod 



Hydro Buff Low Low Mod High 



W Improve Low Low Low Mod 



Histor/Cult Low High Mod High 



Life support is largely biological though obviously dependent on physical and chemical 

 processes. It has moderate site dependency with moderate to nigh size, comnlenity and pristine 

 dependency. It includes production and maintenance of flora and fauna - fbros, grasses, shrubs, trees, 

 fungi, invertebrates, birds, mammals, fishes, herptiles, and microbial populations that are valued for 

 commercial products and recreation. 



Hydrologic buffering is largely a physical function that is extremely site dependent and highly 

 size related. It includes fl()(>d amelioration such as flood water storage/retention, i.e., 

 desynchronization and reductions in magnitude of downstream flows reducing flood water damages 

 during unusual storm events. Conversely, delayed discharges of flood waters augment base flows in 

 rivers and streams supporting diverse aquatic life in our waterways. In some instances wetlands can 

 have an important groundwater recharge function, supplementing other mechanisms to increase total 

 ground water resources. Natural wetlands protecting and supported by groundwater discharge can 

 provide important surface water sources and of course, some wetlands have essentially flow-through 

 groundwater patterns (Clark and Benforado 1981, Gosselink et al 1990, Gosselink and Turner 1978). 



In the water quality improvement function, chemical and physical processes tend to dominate 

 biological processes. This function has moderate site dependency and lower size, complexity and 

 pristine dependency. It includes removal of pollutants/contaminants from inflowing waters - 

 principally surface flows - but it can also include subsurface inflows - to purify natural water supplies. 

 Principle actions include (Faulkner and Richardson 1989): 



1) chemical - oxidation, reduction, cation exchange, adsorption, precipitation; 



2) physical • sedimentation, filtration, precipitation; and, 



3) biological - microbially mediated reactions, assimilation/uptake, nutrient recycling. 



The historical/cultural preservation function is highly site specific and strongly related to 

 natural condition but onlv moderately related to size and complexity of the wetland, ft includes 

 preservation of anthropological and nistorical resources. 



Physical and chemical processes are much less dependent upon complex, diverse and perhaps 

 pristine wetland. A very simple or severely degraded system may nave important hydrologic buffering 

 value and/or water quality improvement values nut little or no life support value. Generally, life 

 support values increase with increasing complexity and proximity to natural conditions. However, a 

 simple wetland (low diversity/complexity) can have very high productivity for certain products. A 

 small system (perhaps 0.1 ha) may have important water quality improvement values but little or no 

 flood amelioration or life support value. Exceptions include very small systems that provide habitat 

 for unusual or threatened or endangered species. Moderate size (>2 ha) systems may have significant 

 hydrologic and life support values and increasing size is related to increasing importance for these 

 values. Obviously, location in the watershed is extremely important to the hydrologic buffering 

 function and moderately important to water quality but may ne much less important to the life support 

 function. Location in a state, region, country or continent may be quite important to the life support 

 function, however. 



Numerous compensatory mitigation projects have failed, and these failures are commonly cited 

 as reasons to deny the validity of the concept. Given the broad variety of wetland types, their 

 geographic distribution, and diverse nature of wetland functional values, generalizations are fraught 



