Environmentalists and economists therefore need not be at opposite ends of the table. Sadly, trade often becomes a weapon to further other political aims because, in the absence of a global policeman to enforce international rules, there are few other ways to impose a country's intent and resolve on others. Environmental problems should be tackled either at their source or through the marketplace in order to maximise efficiency and actually solve the problem. For example, the US could require the labelling of tuna cans so that consumers can state their preferences through the price mechanism, much as organic vegetables and unleaded gasoline command a premium. When it becomes clear to Mexican fishermen that their tuna fetch a lower price, they can then be induced to purchase the more expensive dolphin-friendly nets in order to comply with US regulations.
Consumers win, and the dolphins win too.
If anything, hindering a country's integration into the global economy by way of import quotas and tariffs merely isolates that country and allows it to continue polluting the environment to the detriment of all. Worse, unilateral action on the part of large, powerful nations like the US weakens the global institutions that foster international cooperation. It is difficult to see how such isolationism would help build international consensus in fighting problems like burgeoning carbon dioxide emissions and over-fishing in international waters, problems whose global scope absolutely require the cooperation of all nations. More than half a century ago countries learnt the costs of selfish trade protectionism the hard way, when stiff tariffs and restrictive import quotas exacerbated the demand crash and deepened the Great Depression. Although there is still a long way to go, trade barriers have since been greatly reduced and today we are one step closer to an integrated global economy.