Life on the planet is being homogenized by the expanding human population and the frequent and rapid movement of people and goods, which carry invasive organisms with them. These invasives often flourish in their new ecosystems because, like the woolly adelgid, they have escaped their predators.

Global climate change has become entangled with the problem of invasive species. A warmer climate could allow some invaders to spread farther, while causing native organisms to go extinct in their traditional habitats and making room for invaders.

When a parasite moves to a new habitat, it can find new hosts through a process called the trans-species jump. Often, the new host has no resistance; it and the parasite haven't had time to adjust to each other through natural selection (it is frequently not in the best interest of a parasite to kill its host quickly).

Richard Preston Quotes