Agriculture was the chief economic activity in Guyana. Only the coastal plain, comprising about 5 % of the nation's land area, was suitable for cultivation of crops. Much of this fertile area lay more than one meter below the high-tide level of the sea and had to be protected by a system of dikes and dams, making agricultural development expensive and difficult. In the 1980s, there were reports that the 200-year-old system of dikes in Guyana was in a serious state of disrepair. Guyana's remaining land area is separated into a white sand belt, which is forested, and interior highlands consisting of mountains, plateaus, and savanna.