Those groups lead the way in finding new issues and provide the backbone for grassroots lobbying. One of the effects of the decentralized nature of the movement is a huge amount of tension between various environmental groups. If you think a Libertarian Party convention is contentious, try going to a meeting of different environmental groups. Groups fight over strategy, tactics, and goals. Underlying the outward differences is a competition for members, media attention, and funding from large foundations.
Most environmental activists think that the main conflicts are between national and local groups.
In fact, the real tension is between staffed and volunteer groups. This leads it to broaden its range of activities and makes it more likely to compromise so that politicians will view it as someone they can deal with. The volunteer groups accuse the staffed groups of selling them out. The staffed groups view the volunteers as unreasonable. Meanwhile the staffed groups contend with one another for members and donations, leading to further changes in behavior and further conflicts.