Since 2008, this reserve has been managed through an agreement between the Fundación Naturaleza y Hombre and the Gajano Neighbourhood Council, the Marina de Cudeyo Town Council and an authorisation from the Cantabria Coastal Authority.

The reserve is located at the head of the Ría de Tijero. Its geographical limits are defined by the Bay of Santander to the northwest and the town of Gajano to the north, specifically the districts of El Torrejón and El Puente. To the south it borders the Granja de Heras and the A-8, and to the east Mount Abejo serves as its geographic boundary, near the Pozón de la Yesera.

This reserve has two very different ecological units, although they share a common characteristic, being both form part of a riverside ecosystem. The first of the units is the headwaters of the Ría de Tijero, formed by an intertidal area populated by salty grassland and halophyte vegetation subject to the water logging typical of tidal dynamics. The banks of the estuary, on the other hand, have reeds in the areas of low water depth, as well as riverside vegetation in areas not directly exposed to flooding. One of the tree species most present on the banks is the salt cedar, accompanied by the sea myrtle, where the water splashes offer a saline environment.

The second unit corresponds to the Pozón de la Yesera, a wetland of mining origin from which gypsum was extracted until the mid-1970s. The continuous extraction of the mineral produced the emergence of the water table and the creation of a lagoon vessel. Around it lies the Romanillo stream, one of the streams that supply fresh water to the Tijero estuary. This stream is home to a number of riverbank species, including willows, hazelnuts, some eucalyptus trees and the black locust trees.

After the abandonment of the mining exploitation of the Pozón, the naturalization of the area began, which subsequently led to the appearance and spread of the pampa grass and the illegal incorporation of debris and other waste.

The Environmental Restoration Project for the headwaters of the Tijero Estuary and Pozón de la Yesera (2009) has led to the removal of the debris, the recovery of the water sheet and the use of native trees to compete with the Pampa grass (Cortaderia selloana), and the creation of a small network of paths for public use in the area.

Collaborators:

• Gajano Neighborhood Council.
• Ministry of the Environment, Rural and Marine Affairs. Cantabria Coastal Region.
• Directorate General for the Sustainability of the Coast and the Sea.
• Department of the Environment of the Government of Cantabria.