Throughout history, Marshes have been considered wastelands and their destruction and elimination through reclamation projects has been lauded as progress. However, in recent decades a wide variety of ecological roles and values has been documented, and state and federal governments are acting to prevent indiscriminate destruction of these resources. Government agencies at several levels are responsible for reviewing permit applications for work or disruptions in wetlands areas. By law (PL 95-217), any evaluation for work or alterations must consider all possible aspects of wetlands values. These values are often difficult to quantify, and those which can be assessed usually require extensive studies. Therefore some easily quantified parameters which reflect other functions and roles must be used for marsh evaluation. Because it forms the base of the food web, primary production is one such parameter. This field guide presents methods for estimating net primary production (NPP), which is defined as the amount of plant biomass that has accumulated in a given time interval. In this manual, the estimates are based on a year or the annual growing season. It must be emphasized that this guide only aids in evaluating NPP, one of the several internal and external values of the marsh. Internal values are those which relate to the wetland itself; external values relate to the exchange between the marsh and adjacent ecosystems.

"October 1980." "EPA/600-8-80-037." Errata sheet inserted. Includes bibliographical references (pages 55-57).