When writing an analysis of a text, what must you provide to strengthen your point?

I have no clue if this is right but it maybe could be textual evidence, I don't know for sure though

one of the central themes of edward abbey's work has been his staunch opposition to the glen canyon dam on the colorado river that created lake powell, destroying stunning scenery and wildlife habitat, endangering many rare species of fish and animals, and also irreparably destroying many important archaeological sites which provided information about the early inhabitants of the united states.