everything in the environment. The range 

 of tolerance for the species is greater 

 than the range of tolerance for any one 

 individual. Man is destroying over one- 

 half of the system by changing Susson to 

 a salt marsh because he is doing away 

 with the enormous diversity in the fil- 

 tering capacity of the system. People 

 did not know what they were doing when 

 they decided to take more freshwater 

 from Susson marsh. Soon it will mainly 

 be a saltwater marsh. 



It has been said that no culture 

 that is dependent upon irrigation has 

 ever survived. The Inca culture disap- 

 peared. You can still find the aban- 

 doned agricultural terraces. The Inca 

 culture died out as a consequence of 

 salination of the soils. The same thing 

 happened to the cradle of agriculture in 

 the Middle East. The soils became salty 

 when water evaporated and left dissolved 

 salts on the soil surface. The same 

 happened in Greece — irrigated soils be- 

 came too saline to grow crops. 



The Bureau of Reclamation (BR) has 

 done some brilliant research on this 



problem and they may have resolved the 

 problem with a system of natural filters 

 that are combined with artificial fil- 

 ters. BR drains the agricultural water 

 through the soil and they claim that 

 picks up most of the pesticides. They 

 say they have never found more than a 

 trace of pesticides after the water goes 

 through the soil. Pipes under the soil 

 pick up the wastewater and it is drained 

 through an anaerobic filter. The process 

 is going to be costly because they need 

 to continually feed the anaerobic filter 

 with a carbon salt source. They are go- 

 ing to have to add dried plant material 

 for the anaerobic organisms to feed on 

 as they take up the salts that they re- 

 quire. BR expects to build a long sys- 

 tem of marshes where they hope to keep 

 this water zigzagging back and forth to 

 get the greatest mileage out of the 

 marsh system and to get rid of enough 

 dissolved solids so that the water can 

 be returned to the bay. But the big 

 problem is eliminating the salination 

 of soils in arid regions. We know actu- 

 ally very little about natural filters. 



54 



