Environmental changes are about to invade every aspect of human life (and all life) across the planet. Young people will be particularly affected by these changes; regions where large youth populations are projected to be present in the coming decades are among the most vulnerable to environmental problems. Many young people feel overwhelmed by the impeding threat of environmental destruction and climate change. At Amgueddfa Cymru -- National Museum Wales, the museum youth forum is a club for young people aged 14-25. In 2018, the youth forum brought plastic from local beaches into the museum's natural history displays, transforming the natural history galleries into a platform for showcasing the detrimental impact of pollution on the environment. This article investigates how this youth-led environmental project at Amgueddfa Cymru provided a reality check for the way natural history was portrayed in the museum, and also challenged the museum to become more activist in its stance.