The peat-forming systems at the Usabelartza site are located at the headwaters of the SAC Leitzaran river network.

These mires or acid sphagnum bogs are located on a pass or in a gently sloping area, in which the abundant local rainfall is retained, forming hydromorphic soils which favour formations of this kind. This, together with the local surfacing rocks, predominantly siliceous, allows for the growth of acidophilous flora, capable of withstanding the significant leeching of nutrients and permanently waterlogged soils. Bryophytes belonging to the Sphagnum genus specialise in such conditions and, therefore, thrive at the site. This unevenly-shaped, lobed wetland is divided into areas with a range of plantation forests (Picea sp., Chamaecyparis lawsoniana, Pinus nigra, Larix, sp.) and a large firebreak –70 m wide- that crosses it from east to west. Another relevant factor for the conservation of the area is the presence of a track and a path used by ramblers climbing the nearby summit of Monte Adarra.

MOST IMPORTANT VALUES

Uniqueness
The mires at the Usabelartza site are relevant due to the intrinsic value of such enclaves, which are scattered in amongst distinct habitats, enriching the biodiversity of the mosaic of heathland and plantation forest, as well as providing neighbouring ecosystems with resources, mainly to do with the availability of water (breeding areas and water supplies for fauna, points of recolonisation for species of flora, etc.).

Biological and ecological values
From an ecological point of view, the chief value of the site consists of the acid sphagnum bogs (7140), which, while covering a surface area that may appear modest (5.7 ha), are worthy of note in a regional context (only surpassed by the sites on Monte Gorbeia and Ordunte). Due to the site’s location, midway between the seaboard and the western edge of the Pyrenees (to the northeast) and the mountain regions of the Atlantic-Mediterranean watershed (to the southwest), it contributes to the ecological connectivity of such sites between the coast of the Bay of Biscay and the Pyrenees. It is home to seriously endangered flora species: Drosera intermedia. This insectivorous plant can only be found at three sites in the Autonomous Community of the Basque Country: Jaizkibel and Usabelartza (included in the actions of the TREMEDAL project) and Izki (included in the actions of the LIFE project Pro-Izki). In those areas bereft of plantation forests –the firebreak-, the mires live in equilibrium with priority habitat 6230* Species-rich Nardus grasslands.

Historical and paleoecological values
Usabelartza is home to one of the Autonomous Community of the Basque Country’s few true peatlands, with peat deposits that have survived to our day. In one area, the deposits exceed 150 cm, meaning they are of interest from a paleoecological point of view.

Habitats of Community Interest

• 6230* Species-rich Nardus grasslands.
• 7140 Transition mires and quaking bogs.

Flora
The most noteworthy flora species is the aforementioned Drosera intermedia, listed in the Autonomous Community of the Basque Country as In danger of extinction due to the threat it is under.

Fauna
No specific information on the fauna in the peat-forming areas of Usabelartza is available. Due to its distribution in the Autonomous Community of the Basque Country, the presence of Zootoca vivipara (Viviparous lizard) is likely. As for invertebrates, the presence of the Odonata Onychogomphus uncatus (LC) and Orthetrum coerulescens (not endangered) has been cited.