The Costa Quebrada Geopark is a mosaic of natural environments, including marshes, beaches, dunes, cliffs, riverbanks, and coastal oak forests. These ecosystems host a rich and diverse biodiversity, acting as an essential ecological corridor for numerous species of flora and fauna.

Inland, limestone outcrops shelter the last remnants of coastal oak forests, vestiges of past climates. Pine plantations in the Liencres dune system have created a unique forested area, while hay meadows, dry-stone walls, and hedgerows reflect the traditional agricultural and livestock practices of the region.

The coastal cliffs of Costa Quebrada are of high geological and ecological value. They were shaped by active marine erosion on Cretaceous and Paleogene sedimentary materials, forming intertidal platforms, abrasion terraces, sea cliffs, and scree slopes.

Exposure to salt, strong winds, and temperature fluctuations has allowed halophyte and psammophyte vegetation to colonize these cliffs, including species such as Crithmum maritimum, Armeria pubigera, and Limonium humile. In splash zones, specialized lichens and mosses thrive.

Bird populations, such as the European Shag (Gulosus aristotelis) and the European Storm Petrel (Hydrobates pelagicus), benefit from protection under the EU Birds Directive. The cliffs also host endemic invertebrates, contributing to the ecological connectivity of the Cantabrian coast.

The beaches of Costa Quebrada, including Valdearenas, Canallave, and Arnía, are constantly shaped by sedimentation, erosion, and coastal transport. They support ephemeral habitats of great ecological value, such as embryonic, mobile, and stabilized dune systems (community habitats protected under the EU Habitats Directive: 2110, 2120, 2130).

Dune vegetation includes pioneer species adapted to salinity and burial, such as Ammophila arenaria, Elymus farctus, and Medicago marina. These plants stabilize the substrate and enable ecological succession toward more mature communities.

These areas are critical for vulnerable species such as the Kentish Plover (Charadrius alexandrinus), whose reproduction depends on undisturbed beaches with low human pressure. Vegetation loss, uncontrolled trampling, and coastal development are direct threats.

In the inland areas of the Geopark, especially at higher altitudes or wetter soils, Atlantic deciduous forests remain, including oak woods (Quercus robur), chestnut groves, and mixed broadleaf forests. These are remnants of the large Eurosiberian forests that once covered the Cantabrian region, forming essential ecosystems for biodiversity.

Under the canopy, relict ferns, hygrophilous mosses, and a rich community of saproxylic invertebrates indicate ecological maturity.

Although some forests have been fragmented or replaced by Pinus radiata and Eucalyptus plantations, restoring native deciduous species and improving ecological connectivity are key goals of Natura 2000 conservation plans.

Costa Quebrada’s wetlands include small streams, temporary ponds, and marsh areas such as the reed beds (Phragmites australis) around the Pas estuary and Mogro marsh. Despite their small size, these habitats are ecologically vital: they regulate hydrology, filter pollutants, and provide refuge for high-value species.

Notable fauna includes sensitive amphibians like the Palmate Newt (Lissotriton helveticus) and waterbirds such as the Grey Heron (Ardea cinerea) and the Water Rail (Rallus aquaticus). Riparian zones host typical vegetation, including Salix atrocinerea, Alnus glutinosa, and Carex and Juncus communities, protected under habitats 91E0* (alluvial forests) and 6430 (humid meadows).

These ecosystems are vulnerable to hydrological changes, diffuse agricultural pollution, and invasive species such as Baccharis halimifolia and Cortaderia selloana. Ecological restoration and the protection of riparian corridors are crucial.

Costa Quebrada’s rural landscape, shaped historically by extensive agriculture and livestock grazing, forms an agroecological mosaic of high biodiversity value. Hay and pasture meadows, living hedgerows, dry-stone walls (morios), and linear copses provide shelter for open-habitat birds, small mammals, and a rich diversity of butterflies and pollinators.

Semi-natural habitats such as Atlantic humid meadows (6510) and oligotrophic grasslands (6230*) rely on traditional practices like crop rotation, the use of native breeds, or late mowing. Botanical highlights include Orchis mascula, Leucanthemum vulgare, and Trifolium pratense.

Loss of agricultural activity, intensification, or abandonment leads to habitat degradation, invasive species, and uniform forest plantations. Sustainable management is essential for ecological connectivity and the preservation of intangible rural heritage.

The Geopark’s limestone formations and karst processes have created underground systems of great scientific and ecological interest. Caves and sinkholes, both coastal and inland, maintain stable microclimates and humidity, supporting highly specialized fauna with high levels of endemism and troglomorphic adaptations.