In the Sierra de Guadarrama National Park, nine natural systems, which constitute a representative sample of the Mediterranean high mountain natural systems, such as:
- Supraforest thickets, high-mountain grasslands, high-altitude woody steppes and cascajares
- Pine forests, juniper and Spanish juniper woodlands
- Oak, beech and birch groves
- Complaints and melojares
- Holm oak, holm oak, cork oak and wild olive groves
- Watercourses and riparian forests
- High mountain wetlands and lagoons
- Singular natural systems of glacial and periglacial origin
- Singular mountain and high mountain formations and reliefs
Some of these natural systems, such as supra-forest scrublands, high-mountain grasslands, high-altitude woody steppes and kermes oaks, and natural systems of glacial and periglacial origin, are distributed continuously on both sides of the regional boundary. The joint protection of both slopes, the Segovian and the Madrilenian, under the single figure of National Park will allow a better conservation of these natural systems.
In addition, the Sierra de Guadarrama National Park has an important richness and diversity in relation to flora, fauna and natural habitats.
The diversity of species of fauna consists of 255 registered taxa, which means it is home to 40% of the Spanish vertebrates, and 74 of these 255 species have some level of protection at national or European level. The Park is home to 148 species of birds (40% of Spanish registered birdlife) and 58 species of mammals (almost 50% of Spanish mammal species).
With regards to plant species, 114 species of interest have been recorded, either because they are included in the Catalogs of Threatened or Protected Species of the Community of Madrid or Castilla y León, in the Red List of Spanish Vascular Flora or in Annex IV of the Habitats Directive .
On the other hand, 25 types of habitats within its geographical scope, 4 of which are considered "Priority Habitats". Of these 25 types, 21 habitats have been identified on the Madrid side, 13 on the Segovian side, and 2 are not represented in the National Parks Network.