Before we stopped mowing, the field was a lawn. Several species of grass shorn so short that it couldn't support much biodiversity.
We learned that by giving up on mowing, we could increase biodiversity, so some sections of the field were left to grow. We also found out that deer would eat any unprotected shrubby plant.
Changes occurred as soon as the grass grew. Insect numbers and diversity increased, and in science class, students observed the difference in insect numbers between the mowed and unmowed sections of the field.