One of the arguments for conserving the biodiversity of natural ecosystems is that they may contain many undiscovered plants with medicinal properties. This is possible because evolution has had billions of years to randomly create different compounds. Some of these may have been selected for because of their medicinal value, for example the mold that makes penicilin may have benefitted from its anitbacterial quality. Other compounds may be of value to human health by pure coincidence. That is its human usefulness has nothing to do with how the plants uses the compound. Some pharmaceutical development involves synthesizing and testing thousands of compounds to see if they do anything useful. The worlds ecosystems offer a ready made library of compounds which could be tested in the same manner. The map below shows biodiversity hotspots around the world.

Plants for a Future