HABITAT DESCRIPTIONS 



This section contains descriptions 

 of each of the 20 ecological and eco- 

 nomic habitats identified in this study, 

 accompanied by a map showing the dis- 

 tribution of each habitat. The companion 

 technical report (Costanza et al. 1983) 

 contains detailed data on each of the 20 

 habitats, including energy and matter 

 flow diagrams and input-output tables 

 for eight of the more intensively 

 studied habitats. Figure 17 is an exam- 

 ple of one of the energy and matter flow 

 diagrams from the technical report (the 

 salt marsh habitat) . Table 4 is the salt 

 marsh input-output table that corre- 

 sponds to Figure 17. 



In general, the diagram shows the 

 salt marsh habitat as comprised of four 

 major components: surface water, shallow 

 sediments, primary producers, and con- 

 sumer organisms. The storage tank-shaped 

 symbols represent storages, such as 

 salts, total organic matter, and nutri- 

 ents. The hexagon-shaped components are 

 consumers (heterotrophs) , and the 

 bullet-shaped symbols represent primary 

 producing (autotrophic) components. The 

 entire salt marsh system is enclosed in 

 a bullet-shaped boundary, symbolizing 

 the fact that it is a net producing 

 habitat, i.e., community production 

 exceeds community consumption. Arrows 

 coming from outside of the habitat 

 boundary indicate inputs from forcing 

 functions (shown as circles). These 

 inputs regulate the habitat by providing 

 the matter and energy that it needs to 

 operate. The numbers shown on the ar- 

 rows indicate estimated annual fluxes of 

 matter or energy on a square meter basis 

 (see Costanza et al. 1983). 



The habitat categories used are 

 aggregates of the more than 100 cate- 

 gories recently mapped in the MDPR 

 (Wicker et al. 1980b), using a classi- 

 fication system based on Cowardin et al. 

 (1979). Related habitat categories were 

 lumped in order to limit the models to a 

 reasonable size, and because of the lack 

 of complete information on each specific 

 category. Table 5 lists the areas of 

 each of the aggregate habitats in the 



total MDPR for the two years, 1955 and 

 1978. 



The amount of information available 

 on each habitat varied considerably. 

 Some habitats, such as cypress swamps 

 and salt marshes, have been studied in 

 more detail than others. This uneven- 

 ness of information is reflected in the 

 habitat descriptions and in the level of 

 detail of quantitative information pre- 

 sented . 



AGRICULTURE (1) 



Agricultural habitat in the MDPR 

 occupied about 98,000 ha (242,000 acres) 

 in 1978, or almost 3% of the total area 

 (Figure 18). Total agricultural area 

 declined from 132,000 ha (326,000 acres) 

 in 1955 to 98,000 ha in 1978, (Table 5), 

 mainly as a result of increases in 

 urban-industrial uses. 



The major agricultural products in 

 the MDPR are sugarcane, soybeans, 

 tobacco, pasture and livestock, fruits 

 and nuts, and vegetables. The major 

 cultivated areas in the MDPR are the 

 natural levees along the distributaries 

 of the Mississippi River. These levees 

 consist of rich alluvial soils which, in 

 combination with a long growing season 

 (245 frost-free days), abundant rainfall 

 (140-152 cm/yr or 55-60 inches/yr) , and 

 easy access to low cost water transpor- 

 tion, support one of the most productive 

 agricultural systems in the country 

 (Larson et al. 1980). 



Many attempts have been made to 

 extend agricultural areas beyond the 

 levees into low-lying interdistributary 

 basins. However, such undertakings have 

 required the artificial impoundment and 

 draining of wetlands, and most of them 

 have failed or succeeded only margi- 

 nally. Large rectangular lakes, such as 

 those near Clovelly, Louisiana (Bara- 

 taria basin) testify to the effects of 

 pumping water out of wetlands. These 

 lakes are the remains of agricultural 

 wetland reclamation projects (Craig et 

 al. 1979) that were obviously expensive 

 mistakes, both for the developer and for 

 the natural system. 



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