Answer:
It suggests that the rapid transfer of plants, animals, and disease may have unknown effects.
Step-by-step explanation:
In this text, the author tells us that the way plants and animals are transferred globally nowadays is an event that has never been seen before in the history of the world. The author uses this phrase to show how unprecedented this event is. The purpose of showing this is that it suggests that such a transfer might have effects that we cannot imagine or predict.