The fauna presents a wide diversity that is due in large part to the geographical position of the Iberian peninsula between the Atlantic and the Mediterranean and between Africa and Eurasia, and the great diversity of habitats and biotopes, the result of a considerable variety of climates and well differentiated regions.

The vegetation of Spain is varied due to several factors including the diversity of the terrain, the climate and latitude. Spain includes different phytogeographic regions, each with its own floral characteristics resulting largely from the interaction of climate, topography, soil type and fire, and biotic factors. The country had a 2019 Forest Landscape Integrity Index mean score of 4.23/10, ranking it 130th globally out of 172 countries.

Within the European territory, Spain has the largest number of plant species (7,600 vascular plants) of all European countries.

In Spain there are 17,804 million trees and an average of 284 million more grow each year.