There is a compelling explanation on this AFL-CIO website about why sustainability activists should stand with strong unions.
The heart of the argument is reproduced below, and it certainly resonates in Wisconsin, where collective bargaining is being reduced in the public sector the same time that transit funding, wetlands preservation, and clean air and water programs will be cut in the proposed 2011-2013 budget, by separate legislation in a coordinated and ideological push towards privatization:
"1. Organized labor is the most powerful force for fighting conservative ideology. If unions “melt away,” American politics will be totally dominated by a combination of corporate greed, right-wing media and tea party extremism.
"2. Despite occasional elements of discord, the alliance of labor, environmental and sustainability movements has been crucial ever since the first Earth Day in supporting and passing environmental legislation. It will continue to be crucial in the future.
"3. The right-wing strategy is to divide progressive groups that should be natural allies and play them off against each other. For example, they are attempting to drive a wedge between private-sector and public-sector workers. Similarly, they constantly harp on the theory that environmental protection will destroy workers’ jobs — while implying that workers have no interest in protecting the environment.
"4. The most promising strategy for reviving popular support for sustainability policies is a program to create full employment by creating millions of green jobs protecting the climate and the environment. Organized labor has been a major supporter of green jobs. If unions “melt away,” so will a major pillar of support for environmental policies that create jobs.
"5. Unions are far more likely to support sustainability policies if in their hour of need they receive support from sustainability activists. The support of groups like the Sierra Club for right-to-organize legislation played a significant role in encouraging unions to support climate legislation, for example. It helped to persuade the Teamster’s to reverse its position on Arctic drilling and pull out of the coalition that supports it.
"6. Even when they differ on particular issues, unions are the most important allies of sustainability activists in the political arena. Unions recently spent more than $200 million to defeat candidates who are threatening to break the labor movement. In virtually all cases they are the very same candidates who are trying to gut environmental protection policies and who claim global warming is a myth. Even on the minimal basis of “the enemy of my enemy is my friend” sustainability activists should be try to keep organized labor from being “cut off at their knees.'”