A dynamic systems model of how an ecosystem stores and cycles carbon, and what happens to that balance when you start removing trees. It runs across the seasons, so the climate shifts through the year instead of sitting still.
The question was how much deforestation an ecosystem can absorb before its carbon storage stops bouncing back. The model tracks carbon moving between the trees, the soil, and the air, and lets you push the amount of forest loss up and down to watch where the balance tips.
I wrote it in R and presented what it showed to a full lecture hall.