and some legal determinations have afforded more protections to these environmental uses of water.
In air pollution control, several effects transcend the normal boundaries of the program. In the climate change program, for example, it is widely recognized (Ekins, 1996) that the control of greenhouse gases will result in substantial reductions of other pollutants as a side effect. Other, more detrimental, effects include the clustering of emissions either in space or time.
In fisheries two main effects have been bycatch and highgrading. Bycatch is a problem in many fisheries, regardless of the means of control. The evidence from fisheries on how the introduction of ITQs affect bycatch and highgrading is apparently mixed. Two reviews (National Research Council, 1999:193; Organization for Economic Co-operation and Development, 1997:83) found that bycatch and highgrading may increase or decrease in ITQ fisheries depending on the fishery.
Although the evidence on environmental consequences is mixed (especially for fisheries), it is somewhat clearer for the economic consequences. In the presence of adequate enforcement, tradable permits do appear to increase the value of the commons to which the permits apply. In air pollution control, this takes the effect of considerable savings in meeting the pollution control targets (Hahn and Hester, 1989; Tietenberg, 1990). For water it involves the increase in value brought about by transferring the resources from lower valued to higher valued uses (Easter et al., 1998). In fisheries it not only involves the higher profitability from more appropriately scaled capital investments (resulting from the reduction in overcapitalization), but also from the fact that ITQs frequently make it possible to sell a more valuable product at higher prices (fresh fish rather than frozen fish) (National Research Council, 1999). One review of 22 fisheries found that the introduction of ITQs increased wealth in all 22 (Organization for Economic Cooperation and Development, 1997:83).
In both water and air pollution, the transition was not from an open access resource to tradable permits, but rather from a less flexible control regime to a more flexible one. The transition apparently has been accomplished with few adverse employment consequences, though sufficient data to do a comprehensive evaluation do not exist (Goodstein, 1996).
The employment consequences for fisheries have been more severe. In fisheries with reasonable enforcement, the introduction of ITQs usually has been accompanied by a considerable reduction in the amount of fishing effort. Normally this means not only fewer boats, but also less employment. The evidence also suggests, however, that the workers who remain in the industry work more hours during the year and earn more money (National Research Council, 1999:101).