Description of the  Aiako Harria PIC:

The “Aiako Harria” PCI is located on the eastern edge of Gipuzkoa. It stretches from the River Bidasoa to the River Urumea, which is the southern boundary with the Autonomous Community of Navarra. Both rivers are the ES2120018 and ES2120015 PCIs respectively.

Located in the Atlantic biogeographic region, it can be broken down in various sectors by their environmental features. The southern part is mainly covered by natural forests (oak and beech woods) and forestry plantations, with areas used for grazing. The presence of natural habitats of interest accounted for 30% of the surface area of the PCI in 2000. The central zone includes the Aiako Harria granite massif, which rises up to 834 m high at its highest point.  It is a major point of reference, with unusual features due to its geographical special features. -

The northern part (Endara Ravine) includes the spurs of the Aia massif, whose steep slops are mainly covered with woods and with frequent rocky outcrops. The lower part of the River Bidasoa is the lowest point at 6 m.  However, most of the area (71%) is between 200 and 500 metres above sea level.

Thanks to its position in the foothills of the Pyrenees, the Aiako Harria massif is the first condensation point for the humidity that is brought from the Bay of Biscay, which explains the high rainfall. The annual rainfall is over 2000 mm in the valleys, while it reaches 2800 mm on the peaks.  Winter is the period with the heaviest rainfall.

The land dates back to the Paleozoic era and forms the western tip of the Pyrenean axial zone: plutonic rocks (fine granite and granodiorites) and their metamorphic  aureole (pea stones, greywackes, etc.) The geological interest is accentuated by the presence of mining seams, some of which are known and where mining took place as far back as the Roman era. The soil is mainly acidic, which is clearly reflected in the vegetation in the area.

The main use of the land is forestry, which is the case throughout the majority of the territory: beech and oak forests, together with deciduous and coniferous forestry plantations. Extensive grazing is widespread in the higher area and is more scattered in the rest of the territory. There are very few farmsteads within the zone and are scattered throughout the area. The proximity of the urban centres along the eastern border of Gipuzcoa means that this area plays a very important recreational role and is popular with hikers, mountaineers and picnic groups.

The Añarbe reservoir supplies water to half the population of Guipuzkoa, around 300,000 people. Other reservoirs, water collecting areas and channels for supply or hydroelectric purposes are located in this area.

The territorial spheres of the PCI is divided between five Gipuzkoa municipal districts: Irun, Oiartzun, Errenteria, Hernani and Donostia. The primary sector plays a very small role, while industry and the service sector are the main sources of revenue. That is why these municipal districts show little dependency on the dynamics arising from the use of Aiako Harria. In addition, there are no inhabited settlements inside the PCI, even though there are a few odd farmsteads, particularly in the Oiartzun municipal district.

The urban centres are large (9,200 – 178,400 inhabitants) and their total population amounts to around 300,700 people. The Historical Territory of Gipuzkoa has a population of 673,500 inhabitants and the two closest regions to the PCI, Donostialdea and Bajo Bidasoa are home to 45% of the total population. This conditions and clearly encourages the public and recreational use of the PCI by this potential population of users. There are an estimated 575,037 visits each year, with studies that show that the population nearest to the Natural Park are aware of its existence.

Public ownership, in the form of  Public Utility Forest (Montes de Utilidad Pública), is predominant and accounts for 83.2% of the surface area. This implies comprehensive use of the woodland and care of the forests. This fact contracts with the situation of forestry ownership in the rest of Gipuzkoa, where the forests are mainly privately owned (80% of the total).        

The Public Utility Forests (M.U.P.) located in the Aiako Harria PCI and their owners are as follows:

Woodland	Ownership	Surface area (ha)
M.U.P. 2045.1 Erlaitz-Pagogaina	Ayuntamiento de Irun	751,5
M.U.P. 2063.1 Pikokarate	Ayuntamiento de Oiartzun	351,7
M.U.P. 2063.2 Kausua	Ayuntamiento de Oiartzun	536,1
M.U.P. 2063.3 Martuzenegi	Ayuntamiento de Oiartzun	839
M.U.P. 2063.4 Zaria	Ayuntamiento de Oiartzun	780,1
M.U.P. 2067.1 Añarbe	Ayuntamiento de Errenteria	1671,7
M.U.P. 2040.1 Aparrain	Ayuntamiento de Hernani	116,5
M.U.P. 2040.3 Usoko-Epelerreka	Ayuntamiento de Hernani	268,6
M.U.P. 2069.1 Errekabeltza	Ayuntamiento de Donostia	123,7
Oberan	Ayuntamiento de Donostia	87.8
M.U.P. 1040.1 Urdaburu	Diputación Foral de Gipuzkoa	83
TOTAL		5.609,7