The photographs accepted in the contest Wiki Loves Earth 2021 are those showing protected natural sites listed in this page of the Ministry of Environment and belonging to the paneuropean project Natura 2000 called Special Area of Conservation abbreviated in SAC (in Spanish Zonas Especiales de Conservación, ZEC). Furthermore the correposponding identifier of the site must be included in the description page of the picture. In addition to the maps you can find below for each autonomous community, there is a paneuropean map that includes the SACs (in blue) with their delimitations.
Lugares de Importancia Comunitaria (LIC) and Zonas Especiales de Conservación (ZEC) in Spain
*Listings in other languages could contain entries that do not correspond to any SAC of the Natura 2000 network, and therefore don't fulfill the contest rules.
In adition to the listings of the Ministry of Agriculture, Food and Environment, in Wikipedia you will find listings with all SACs of Nature with links to Wikipedia articles, already existing images, along with Wikimedia Commons categories:
Wiki Loves Earth 2021 - Wikimedia España - CC-BY-SA 4.0