The opposite of "exterminate" is to "preserve" or "protect." Preservation is the act of maintaining or guarding something from harm or damage. People tend to preserve things that are of value to them, from ancient artifacts to rare species of plants and animals. Protecting something can involve taking measures to prevent dangers or threats from causing harm. Alternatively, the word "cultivate" can serve as an antonym for "exterminate." Cultivating involves encouraging growth, development, and improvement, such as when farmers take care of their fields or gardeners tend to their plants. By cultivating instead of exterminating, people can help preserve and enhance the natural world around them.