"Environmental work" is slightly more general but includes "environmental protection work". The two phrases are usually interchangeable, especially if there is any establishing context.
"Environmental work" could also refer to work that is not strictly protectionist, such as basic research on understanding the environment, but in most cases that would probably be phrased "environmental research" or something like that. Even then, most researchers studying the environment do so with the intention of protecting it.
Either phrase would likely be taken to mean the total work in general rather than a specific project, unless there is only one relevant project anyway. If you do want to refer to one specific effort, you could do so explicitly, such as "our recent environmental work", "this environmental work", etc.