The Fitzgerald Biosphere Reserve lies on the southern edge of the Yilgarn Block and the adjoining Albany-Fraser Province. The bedrock of the northern edge of the biosphere reserve forms part of an ancient crustal segment known as the Yilgarn Craton. Granite and gneiss are the predominant rock types with minor enclaves of altered sedimentary and mafic igneous rock. Skeletal soils are associated with granite exposures and extensive areas of shallow loamy sand.

The region boasts huge diversity in plant species including the only remaining example of wet sclerophyll (with thick, leathery leaves) forest, dry sclerophyll forests, coastal woodlands and scrub, several major river systems, lakes and swamps, and remnants of biologically important woodlands and shrublands belonging to the wheatbelt. The region ranks among the most important areas for plant biodiversity in the world and contains over 800 rare and threatened plant and animal species, about many of which little is known. Of the 5,000 or so vascular plant species native to this area, 79% are endemic.

Environments within the upland plains are important for threatened terrestrial mammal and bird species. Examples of endangered species include the western ground parrot (Pezoporus wallicus fusciventer), the Carnaby’s black cockatoo (Calyptorhynchus latirostris) and the dibbler (Parantechinus apicalis). Other animal species include the western quoll (Dasyurus geoffroii), the quenda (Isoodon obesculus fusciventer), the tammar wallaby (Macropus eugenii), the mallefowl (Leipoa ocellata) and the peregrine falcon (Falco peregrinus).