These indirect and cumulative changes are the most 

 significant long-temi impacts of human activity in the 

 Chenier Plain. 



Natural and man-induced changes, in the habitat 

 composition of a basin can be either desirable or un- 

 desirable depending on one's point of view. It is rare 

 that a change is either wholly desirable or wholly un- 

 desirable in terms of man's interest in natural resources. 

 For example, hurricanes modify wetlands, kill many 

 wetland aniinals, increase soil salinities, and cause ex- 

 tensive damage to cultural features. On the positive 

 side, the flood waters clear clogged waterways of nui- 

 sance floating vegetation, release organic detritus 

 from the upper marshes to open waters bodies (Craig 

 et al. 1979), and destroy perennials in the fresher 

 marshes which are replaced by annuals that are more 

 desirable as food for waterfowl (Louisiana Department 

 of WUdlife and Fisheries 1959). Cultural features, 

 such as canals and spoil deposits, often increase the 

 extent of saltwater intrusion, alter historic flow pat- 

 terns and, in some instances, cause impoundment or 

 drainage of large areas of wetland. However, spoil 

 banks provide areas suitable for nesting aUigators and 

 provide avenues of wetland access for deer and other 

 mammals. 



Of the 14 habitats described for the Chenier Plain, 

 all have undergone some change in their relative area 

 over the past 25 years (table 3.55 and app. 6.4). The 

 habitats Usted in this table do not correlate exactly 

 with the 14 habitats previously described. The four 

 natural marsh habitats have been combined since there 

 was no accurate method to determine the 1952 dis- 

 tribution of each wetland habitat individually. The 

 ridge habitat was divided into two categories: natural 

 and spoil. This distinction was warranted since natural 

 ridge habitat is being lost and spoil areas are increas- 

 ing. The agricultural habitat was divided into three 

 subhabitats (rice field, non-rice cropland, and pasture) 

 in order to determine whether there were any tem- 

 poral changes in these agricultural subhabitats with 

 respect to land use. 



The total change of 107,000 ha (264,290 a) dur- 

 ing the 23-year period examined is equivalent to 8.1% 

 of the total Chenier Plain area. A more realistic value 

 of habitat change can be obtained by eliminating the 

 changes within the agricultural subhabitats (e.g., rice 

 to non-rice cropland) and by eliminating the nearshore 

 Gulf from area calculations. This results in a total 

 change of 93,000 ha (229,808 a) or 9.8% of the total 

 inland area. 



3.4.5 HABITAT CHANGE BY DIRECT HUMAN 

 ACTION 



It is apparent (table 3.55) that culturally-modified 

 habitats are increasing in size. As of 1975, pasture, 

 urban and impounded marsh habitats, and spoil and 

 agriculture areas represented 38.5% (287,434 ha, 

 710,265 a) of nonaquatic habitats in 1974 and only 

 31.2% (232,717 ha, 575,056 a) in 1952. This increase 

 was at the expense of natural habitats. 



Table 3.55. Net habitat change in the Chenier 

 Plain from 1952 to 1974^. 



*1954 to 1974 for the East Bay Basin. 

 Includes salt, brackish, intermediate, and fresh marsh. 



The net increase of 38,1 12 ha (94,177 a) of im- 

 pounded marshes accounts for most of the 54,717 ha 

 (132,209 a) increase in culturally-modified habitats. 

 For the most part, these areas are privately owned, al- 

 though some of the increase is the result of estabhsh- 

 ment of wildlife refuges in the Texas portion of the 

 Sabine Basin during the period between 1952 and 

 1975. The privately owned impounded areas are used 

 for several purposes. Some may eventually be drained 

 for agriculture. Many areas were established for com- 

 mercial recreation purposes, largely for waterfowl 

 hunting. Others were created to prevent land loss 

 (which decreases the number of possible land uses). 



The urban habitat has increased by 5,446 ha 

 (13,457 a) over the same period. About one-fifth of 

 this increase was at the expense of fresh marsh. Most 

 of the increase, however, was at the expense of up- 

 land habitats. Thus, residential areas, and industrial 

 and commercial complexes have expanded at the ex- 

 pense of agricultural lands, ridge, upland forest, and 

 (despite the threat of hurricanes) beach habitats. Con- 

 tinued expansion of the residential component will 

 probably occur at the expense of upland agricultural 

 areas. However, that portion of the industrial sector 

 that requires access to navigable waters will probably 

 expand at the expense of wetlands or inland open 

 water habitat because of the lack of better drained 

 land remaining along these waterways. 



Althougli some agricultural land has been con- 

 verted to other socioeconomic uses, there has been a 

 net increase of 5,794 ha (14,317 a) between 1952 



78 



