AI-Generated vs. Human-Created Sustainable Advertising: Effects of Source Disclosure and Environmental Claim Strength on Perceived Greenwashing and Green Trust Among Generation Z Consumers

The rapid integration of generative artificial intelligence into digital advertising, combined with growing consumer concern about greenwashing, has created a dual credibility burden in which sustainability messages must be evaluated for both environmental truthfulness and authenticity of authorship—a challenge intensified by emerging AI disclosure regulations such as Article 52 of the EU AI Act. This study investigates how ad source (AI-generated vs. human-created), source label (labelled as AI vs. labelled as human), and environmental claim strength (vague vs. strong) jointly influence perceived greenwashing and green trust among Generation Z consumers. A 2 × 2 × 2 mixed factorial experiment was conducted with 154 undergraduate participants randomly assigned to one of four source–label conditions and exposed to both vague and strong environmental claims; data were analysed through one-way ANOVAs with Tukey HSD post hoc tests and paired-samples t -tests. All eight hypotheses were supported: AI attribution consistently elevated greenwashing perceptions and depressed green trust, while strong claims significantly reduced greenwashing perceptions and elevated trust within both correctly disclosed conditions. Most notably, the disclosed label—rather than the actual generative source—emerged as the dominant psychological cue, with human content mislabelled as AI suffering the same credibility penalty as genuine AI content. The findings reveal a transparency paradox with significant implications for AI disclosure regulation and sustainable marketing practice.