MISSISSIPPI RIVER DIVERSIONS, COASTAL WETLAND RESTORATION CREATION AND AN ECONOMY OF SCALE/

We tested the hypothesis that there is an economy of scale in ecologic al engineering projects designed to create or restore wetlands by usin g examples of coastal restoration/creation projects in the Louisiana c oastal zone. Land gain and project cost are directly related to the am ount of riverflow diverted from the main channel, as expected. However , the $/ha gained was dramatically and directly related to project siz e. A 1000 fold increase in project size is matched by a 100 fold incre ase in the cost/ha gained. The smallest river diversion projects ($20, 000 each) create land at slow rates (@5 ha/year) and tend to be very c ost effective ($20-$500/ha). These low cost/ha gained are in sharp con trast to that of the larger river diversion projects and most other lo cal wetland restoration/creation projects funded by state/federal spon sored programs ($1000 to $100 000/ha) on this coast. There is a 15 fol d increase in $/ha gained as project size increases by a factor of 10. This situation of decreasing returns ($/ha gained) with project incre asing costs may be called an 'inverse' economy of scale. We propose th at there are generic economies of scale inherent to similar environmen tal management approaches that represent a compromise of at least thre e attributes: attempts to control ecosystem behavior (predictability a nd use), ecosystem complexity, and incomplete ecosystem knowledge. (C) 1997 Elsevier Science Ireland Ltd.