The area of shrimps farmed in Tam Giang Lagoon expanded at an average rate of 400% each year from 1995 to
2004 (Truong, 2012 p. 53). After peaking at 4,000ha in 2004, the area fell steadily to 2,700ha in 2008
following persistent and widespread outbreaks of disease in the Lagoon. Hop et al. (2005) and Thung (2007)
conducted experiments that showed some alarming indicators of deteriorating water quality in the Lagoon between
1998 and 2004. These indicators included diminishing levels of diffused oxygen (i.e. an increase of organic
pollution) - especially in places close to crowded shrimp farming areas, greater nutrient loads entering the lagoon
and less absorptive capacity of the natural environment - conditions conducive to eutrophication, higher levels of
total coliform density, and higher levels of organochlorine pesticides in the sediment. Water pollution poses a
serious threat to all farmers who raise shrimps in the Lagoon and the resultant yield risk is not only co -
variant (i.e. risk that simultaneously affects the vast majority of producers) but also systemic (i.e. it creates
risk for other agents in the chain). It is estimated that some 100,000 poor people rely directly on aquaculture
and capture fisheries in TGCG Lagoon as their main livelihood activity (Tuyen et al., 2010).