Introduction
We humans have an enormous impact on our planet. Our activities have transformed over half of Earth's land surface and have altered the composition of the atmosphere, leading to global climate change.
We have introduced many species to new regions, an action that can have severe negative effects on both native species and human economies. Even the oceans, seemingly so vast, show many signs of environmental degradation due to human activities, leading to declining fish stocks; widespread bleaching of once-spectacular coral reefs; the formation of large “dead zones,” regions where oxygen concentrations have dropped to levels low enough to kill many species; and acidification.Global changes like those we've just described can occur when humans take actions without giving much thought to how our actions might affect the environment. In such situations, we have repeatedly been surprised by the unintended and harmful side effects of our actions. Fortunately, we are beginning to realize that a better understanding of how the natural systems of our environment work can help us to anticipate the consequences of our actions and fix the problems we have already caused.
Our growing realization that we must understand how natural systems work brings us to the subject of this book. Natural systems are driven by the ways in which organisms interact with one another and with their physical environment. Thus, to understand how natural systems work, we must understand those interactions. Ecology is the scientific study of how organisms affect—and are affected by—other organisms and their environment.
In this chapter, we'll introduce the study of ecology and its relevance for humans. We'll begin by exploring a theme that runs throughout this book: connections in nature.