The Earth existed long before humans evolved, and throughout its history, many different types of life have survived and thrived. The introduction of an outside influence (human or otherwise) that throws off an ecosystem’s balance is one of the main reasons that nature’s systems fail. Through the relationships between the species around Willodeen’s village—the hummingbirds’ disappearance, Quinby’s appetite, and the blue willow trees that aren’t thriving­—Willodeen shows the importance of balance in nature.

In Chapter 18, Willodeen observes that nature is like knitting a sweater: “You pull one string too hard, and the whole thing starts unraveling” (102). The relationship she uncovers between screechers, blue willows, and hummingbears shows this theory at work. The screechers eat peacock snails that live near blue willow roots, keeping the snail population at a level that allows hummingbear bubbles to adhere to the blue willow leaves. The bounty on screechers is the string that’s pulled too tightly here; it reduces the screecher population around the village, which leads to the snail population overrunning the blue willows and changing the makeup of the leaves. Returning screechers to the ecosystem allows nature to balance itself, but while removing the screechers caused the problem, screechers are not the only cause.