When trees are removed and no new ones are planted, roots no longer grip the ground — and rain washes loose dirt away. This experiment makes that difference visible. You set up two trays side by side: one with grass growing in soil, one with bare soil and no plants. Pouring the same amount of water onto each at the same angle, a paper towel filter at the bottom catches whatever soil gets displaced. The bare soil tray loses far more dirt than the one with grass, showing exactly how clearing a rain forest speeds up erosion.