In the middle ages, Christianity promoted the idea that God created the earth for man's benefit.  However, the Christians opposed any destruction of the natural world.  During medieval times, the Church exerted its power over those thinking and learning about nature.

Books such as Physiologus and Pliny's Natural History were widely read by those curious about nature and the environment.  Medieval authors wrote books about real and fictional beasts, though the study of nature soon improved.

Translations of Aristotle's books increased interest in the natural sciences.  St. Thomas Aquinas developed Aristotle's theories and combined them with theology. 

Albertus Magnus discussed zoology, botany, and mineralogy.  He thought that underground bodies of water were responsible for rivers, but accepted Aristotle's theory concerning volcanoes.

In De Animalibus, Albert rejected the claims about the bestiaries and did some limited grouping of different animal species.  His work brought back the topic of nature to philosophy.

A ThinkQuest site on Pliny

Pliny the Elder