It is important to note that absolute scarcity doesn’t have to be on the horizon in any given resource category for this scenario to kick in. A lack of adequate supplies to meet the needs of a growing, ever more urbanized and industrialized global population is enough. Given the wave of extinctions that scientists are recording, some resources -- particular species of fish, animals, and trees, for example -- will become less abundant in the decades to come, and may even disappear altogether.