Environmental Science in the Coastal Zone Issues for Further Research (1994) / Chapter Skim
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7 Landscapes and the Coastal Zone by R. Eugene Turner
7 Landscapes and the Coastal Zone by R. Eugene Turner
Pages 85-106
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From page 85... ...
INTRODUCTION Scientists and resource managers often look at the coastal zone without referring to the larger landscape in a quantitative way. A conspicuous management practice illustrating the dichotomy between the landscape scale of examination and management action involves permit decisions.
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From page 86... ...
The third example (coastal Louisiana) discusses the indirect impacts of many small dredge and fill permit decisions an in situ change on wetland losses.
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From page 87... ...
Landscapes and the Coastal Zone 00000 00000004 100 1 0000 1 000 100 1 0 1 0000 1 000 100 10 1 1 1 00 1 0 1 0.1 0 01 87 Estuarine Drainage (km) 1 Water Surface (km)
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From page 88... ...
FIGURE 7.2 The relationship between intertidal vegetation and penaeid shrimp yields from the estuaries of the northern Gulf of Mexico. (Source: Turner and Rabalais, 1992~.
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From page 89... ...
These land use changes have led to the loss or destruction of about one-half of the natural Everglades ecosystem through either direct habitat loss or the indirect influences of development. In particular, water movement through and within the naturally defined ecosystem has been modified through land use, land drainage, and both water diversions and storage (e.g., in 1990 there were more than 1400 miles of canals, 65 major spillways, and hundreds of water control structures; Figure 7.5)
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From page 90... ...
. 1970s 1990 coastal ground-water levels significantly reduced from the 1940s (e.g., Klein 19731; Big Cypress waterflow changed from slow, prolonged southward sheetflow overland to accelerated and shortened-period runoff through canal system; water quality problems (e.g., algal blooms)
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From page 91... ...
Landscapes I the Coastal Zone ,_ At' ~ ~me ~~ 1 ~ 3~ 1 vow `1 ~ at. _1 FIGURE 7.5 The hydrology of south Florida around 1900 (left)
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From page 92... ...
Fleming, unpublished size: (1971-1982) based on computer model · percent occurrence of nest flooding: 7 % 19% Wading birds, nestingin 77-93,000 9,850 Ogden end Johnson, 1992 central-south Florida: (1931-40)
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From page 93... ...
; · soil subsidence and water-level declines since 1900 through much of the ecosystem are measured in feet, not inches (Alexander and Crook, 1973~; · agricultural fertilizers leak to downstream ecosystems; · fires are more frequent (e.g., Stephens, 1969~; · perhaps a dozen species whose recovery is compromised by the altered hydrologic cycles are endangered or threatened by extinction; · significant legal issues arise over the allocation of water resources and the aualitv of that water: · the long-term sustainability of drained agricultural lands is in doubt; · saltwater intrusion is a threat to urban water supplies; and, · changes in animal populations occur for those species dependent on plants and their predators/decomposers. ~, CASE HISTORY: MISSISSIPPI RIVER WATERSHED NUTRIENT ADDITIONS The Mississippi River watershed is 41 percent of the area of the contiguous 48 states (Figure 7.6~.
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From page 94... ...
~ .0 ~1 905 60 1 20 1 80 240 Silicate p9 utt1 FIGURE 7.7 Average annual nitrate and silicate concentration in the lower Mississippi River. The data are from the U.S.
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From page 95... ...
Diatoms out-compete other algae in a stable and illuminated water column of favorable silicate concentration. When nitrogen increases and silicate decreases, flagellates may increase in abundance (Officer and Ryther, 1980)
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From page 96... ...
· . J F t1 A M J J A S D ~D All Month Months FIGURE 7.8 Seasonal nitrate concentrations in the lower Mississippi River.
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From page 97... ...
Top: Nitrogen (as N) fertilizer use in the United States and average annual nitrate concentration from 1960 to 1985.
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From page 98... ...
Indirect impacts result from the longer wetland drying cycles, even in semi-impounded wetlands, as a consequence of altered water movements into and out of the wetland. The lengthened drying periods promote soil oxidation and subsequent soil shrinkage (Table 7.3)
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From page 99... ...
Landscapes and the Coastal Zone 99 FIGURE 7.11 Aerial photograph of Louisiana coastal wetland. The dredged canals are usually straight, and He spoil is piled alongside in a continuous line.
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From page 100... ...
31.253.9 Mean Water Level (cm; annual average) 1.713.99 Volume Exchange (wetland surface)
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From page 101... ...
Water movements below ground are thus decreased, both because of the reduced cross-sectional area and the reduced permeability of material beneath the levee. The combined effects of sediment deprivation, increased wetland drying, and lengthened soil flooding result in a hostile soil environment for plants.
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From page 102... ...
. I ' I ' I ' I ' I ' ~ ' 1 ' 1 '' 1 ' I 0 0.05 0.1 Canal Area/Wetiand Area FIGURE 7.13 The relationship between canal density and indirect wetland loss rates (wetland change excluding the area lost to canals and development)
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From page 103... ...
1974. A Preliminary Investigation of the Effects of Water Levels on Vegetative Communities of Loxahatchee National Wildlife Refuge, Florida.
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From page 104... ...
1986. The effect of Mississippi River delta lobe development on the habitat composition and diversity of Louisiana coastal wetlands.
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From page 105... ...
1987. Spoil banks: Effects on a coastal marsh water level regime.
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From page 106... ...
1983. Productivity gradients in salt marshes: the response of spartina alternflora to experimentally manipulated soil water movement.
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