To clarify some definitions. By Anarcho-Syndicalism I mean that neighbourhoods and workplaces would be run as direct democracies through popular assemblies in the absence of a state. And by Environmentalism I mean the desire to create 'harmony' between the natural world and human constructed environments (like cities and farmland).
If you had community groups that would be aware of proposals to construct environmentally damaging projects nearby (since people who live in a community tend to know more about what's being built and done around them) you could either block its proposal (since they control the surrounding land) or carry out direct actions against it (as seen in Esquel, Argentina did in 2002 or in Istanbul, Turkey did in 2013). If workers controlled industry, communities could contact unions and ask for help (as happened in Australia across the 1970s with the 'Green Bans', saving numerous areas of the natural environment from destruction) not to mention that workers' control could bring with it its own wave of sustainability, see the Lucas Aerospace Plan and Bruderhof Factories as examples.
You could argue that direct democracy isn’t a guaranteed method to stop environmental destruction, as a majority of the community might want to destroy the environment. But if everyone in a community wants to destroy the land they live on, how would literally any other system stop this? Any government agency regulating the area would just be bought off by corporations (as they are now) or wouldn't risk the political losses of making such an unpopular move.
Or maybe an anarchist community would pollute in a way that punishes other communities (like dumping pollutants into a river that flows into a lake that supplies another community, but then that other community would just negotiate through the confederation with them to stop or if things got too bad, could just carry out direct actions and sabotage to stop it. It might sound bad, but it’s worst case scenario resembles the best examples of environmental action under the current system, and at it’s best it creates a sustainable civilisation.
So, environmentalists (who aren't anarchists or socialists), what do you think of this approach? What are some criticisms you have of it? What other systems could do the job better?
Also, if you're not an environmentalists and are just here to attack anarcho-syndicalism I'm not going to respond because you've missed the point of the post.