Imagine you’re walking in a rainforest. It’s rich with life --- verdant, beautiful, and diverse. When you look up, you notice something striking. A few giant mahogany trees dominate the forest. Their canopy covers almost everything. After reflecting some on the presence of these trees, you give them reverence. They are towering, majestic, and they sustain life for a bewildering array of other plants and animals. And yet those smaller plants and animals help sustain the trees, too.