This International Environmental Olympiad capstone issue trains students to combine atmosphere, water, land, biodiversity, and human activity into contest-ready reasoning. It covers planetary boundaries, climate-biodiversity-water feedbacks, environmental justice, tipping points, legacy pollutants, compound events, river field studies, mixed data sources, uncertainty, island states, California wildfires, mining, adaptation budgets, development-conservation tradeoffs, geoengineering, foundation models, nature-based solutions, bioeconomy technologies, net-zero plans, corporate claims, and intervention choice under limited data. The emphasis is integration: tracing mechanisms across systems, reading evidence with uncertainty, and judging solutions by what they measurably change.