reflected In fishery harvest differences 

 among hydrologic units. Harvest data, 

 however, are lacking or of poor quality. 

 The development of quantitative data on 

 carbon flow through hydrologic units 

 should be a major objective of current 

 research. 



2. Hydrologic modifications . Cul- 

 tural changes (e.g., canal construction, 

 spoil bank, and levee construction, and 

 impoundments) disrupt the hydrology that 

 integrates coastal ecosystems. The 

 cumulative effects of hydrologic alter- 

 ations are most apparent at the hydro- 

 logic unit level. 



3. Water quality . Eutrophication 

 and the introduction of toxic substances 

 affect water quality throughout some 

 hydrologic units. The optimal manage- 

 ment of water quality requires knowledge 

 about the fates and effects of nutrients 

 and toxic substances. 



4. Saltwater intrusion . Hydrologic 

 modifications and natural processes have 

 allowed the landward progression of 

 isohalines in many of the drainage 

 basins, resulting in loss of habitat and 

 municipal water supply problems. 



Habitat Level 



1. Human-introduced stresses . Many 

 cultural processes disturb specific 

 habitats. A marsh area may be suble- 

 thal ly stressed by partial impoundment; 

 a body of open water may be made eutro- 

 phic; or the soil in an agricultural 

 habitat may be depleted of organic 

 matter. 



2. Estimation of resource produc- 

 tivity and value . The economy of the 

 MDPR benefits from and depends upon the 

 products and services of various habi- 

 tats. Better estimates of the rates and 

 value of ecological production from each 

 habitat are needed. 



AN ALTERNATIVE APPROACH TO 

 ENVIRONMENTAL MANAGEMENT 



The problem of environmental man- 

 agement was eloquently summarized by 



Garret Hardin (1968) in his essay, "The 

 Tragedy of the Commons." Many important 

 environmental components are "common 

 property resources," for which an indi- 

 vidual's cost and benefit calculations 

 often differ from the costs and benefits 

 to society as a whole. Hardin presented 

 a parable in which shepherds using a 

 commonly owned pasture could be expected 

 to increase the size of their flocks 

 based on their independent cost-benefit 

 calculations until the land would no 

 longer support grazing and the common 

 property resource was destroyed. The 

 moral is that avoiding environmental 

 degradation requires a system of social 

 control. Government performs this func- 

 tion either through regulations (e.g., 

 limiting the number of fish harvested 

 under penalty of fines and imprison- 

 ment); or through taxes and subsidies 

 (e.g., taxing each additional fish 

 caught according to its marginal social 

 cost, or rewarding each fisherman for 

 limiting his harvest). 



Environmental management in the 

 United States, as in most countries, has 

 employed the regulatory approach almost 

 exclusively. Some advocate a tax and 

 subsidy approach, however, since it 

 would mesh more easily with the existing 

 market system. It would allow indi- 

 viduals to continue to make their own 

 decisions, while making them economi- 

 cally aware of the full social costs of 

 their alternative courses of action 

 (Page 1977). To be effective, either 

 the regulatory or the tax and subsidy 

 approach to environmental management 

 requires accurate information on the 

 magnitudes of the social costs involved 

 and how they differ from private costs. 



Environmentalists have been wary of 

 assigning economic value to environ- 

 mental resources (such as an acre of 

 salt marsh) mainly because they perceive 

 that the standard economic methods for 

 deriving these values consistently 

 underestimate their worth (Gosselink et 

 al. 1974). Some have, instead, taken 

 the extreme position that environmental 

 resources are "priceless" or of infinite 

 value. Many of our existing environ- 

 mental regulations reflect this atti- 

 tude, which may have fostered the 

 current scrutiny of such regulations as 



