6805
Wetlands are difficult areas upon which to build housing estates , so dredging part of the wetland down to a navigable channel provides fill to build up another part of the wetland above the flood level for houses .
 Wetlands
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Wetlands