Irrigation runoff from neighboring farms may well have increased the concentration of phosphorus in the local swamp above previous levels, but the claim that the increase in phosphorus is harming the swamp' s native aquatic wildlife is false; the phosphorus concentration in the swamp is actually less than that found in certain kinds of bottled water that some people drink every day. The argument is vulnerable to criticism on the ground that it ['makes a generalization that is unwarranted because the sources of the data on which it is based have not been specified', 'bases its conclusion on two contradictory claims', 'relies on evidence the relevance of which has not been established', 'concedes the very point that it argues against']