The quarries that feed the Cementos Rezola factory, called LARRAKO (Nº 12,675, limestone exploitation that contains the fronts called 1C and 2C) and GORIKO (Nº 12,676, marl exploitation that contains the 1M and 2M fronts) are located near the Pagasarri Mountain, close to the Seberetxe neighborhood and in the Arrigorriaga and Bilbao (Bizkaia) municipalities.
All of them are located at the SW end of the small valley excavated by the Bolintxu river, which collects the waters from the Pastorekorta mount and foothills of the Pagasarri, draining them to the NE, since it is a Nervión-Ibaizábal tributary. The area has a very abrupt relief, with important slopes that in geological terms is located on sheet 61-IV (Basauri) of the Geological Cartography of the Basque Country (EVE).
The obtained materials correspond to the urgonian limestones (Aptiense Medio), rich in lamelibranquio molluscs (rudists) fossils and corals. As underlying materials (Lower Aptian age) fine-grained sandstones and calcareous limolites have been identified at the South and West of the exploitation. Stratigraphically above the quarry limestones, there is another lithological set (Upper Aptian age) of detrital character with chaltites and calcareous limolites, massive sandstones and calcareous gaps, which emerge at the North of the quarry.
The soil of the area is integrated into the UDICO humidityregime, and as for the thermal regime it is integrated into the MESICO, so that together the entire area can be characterized as "udico-mesico".
Around the quarries, the following soil units can be distinguished: bare, rocky soil; lithosols-entisols, on limestone material; typical Hapludalf and chromic lytic-luvisols; Eutrochrept rendollico-cambisols eutrics-rendzina brown limestone; Haplumbret tipycal-cambisol gleic-distric-umbric-rankers, on sandstones (acidic); soils contributed.
This area has a temperate climate, corresponding to the category "Oceanic – Cbf" of mild summer (the average temperature of the warmest month does not reach 22 °C but exceeds 10 °C for four or more months a year) within the climate classification of Köppen and Geiger.
Talking about phytogeographic, the factory and the quarries are in the Eurosiberian Region, European Atlantic province, Cantabrian-Basque Sector, Santanderino-Vizcaíno District. Overall, the factory grounds have an attractive structural complexity based on different vegetal covers. The most interesting from the ecological point of view are those framed in the phytosociological association Polysticho setiferi-Fraxino excelsioris sigmetum, corresponding to the series of potential vegetation called Temporihigrófila and climatophilic series, Cantabrian-basque, thermo-mesotemperate humid-hyperhumid, hyperoceanic and semihyperoceanic, mesophytic, neutral-basophilic and neutral-acidophilic, of the forests of Quercus robur with Fraxinus excelsior and Polystichum setiferum, also known as Asturian-Basque mesophytic series.
The areas in active exploitation landscape configuration shows a low diversity, with respect to the surrounding area, due to the limitations that extractive tasks represent for ecosystems. However, this apparent landscape diversity lack is replaced by the great potential of the generated habitats, because their ability to house great importance ecological niches. Likewise, these environments can offer opportunities for an interesting variety of species adapted to rock environments, and once the colonization occurs, could end up providing ecosystem services of great value, such as soil support, reduction of wind erosion, control of non-native vegetation colonization, etc.
Roughly speaking, these are the main characteristics of the plant formations around the cement factory:
- Forest harvesting areas: timber harvesting, they are composed mainly of Monterey pine (Pinusradiata) and white eucalyptus (Eucalyptusglobulus) with great development specimens and an abundant cohort of Lianiform species (formed by Smilax aspera, Clematis vitalba, Rubia tinctorum, and Hedera helix). Despite the development of the Lianiform stratum, these formations represent a great simplification of the plant cohort typical of the mesophilic forests of the area.
- Plant colonization areas: they accommodate the initial stages of progressive succession in which, after the alteration of the extractive process, the vegetation evolves towards greater complexity and biomass towards the natural potential vegetation of the area. Discrete herbaceous spots and even some shrubs such as tojo (Ulex cantabrica) and ailaga (Genista hispanica) can be found.
- Mesophytic forest (Atlantic mixed forest): it is about mixed deciduous forest formations, in different stages of succession, based on Atlantic mesophytic oak grove, usually of a certain maturity, with predominance of the arboreal bearing, formed mainly by carballo oak (Quercus robur) accompanied by other species ash (Fraxinus excelsior), alder (Alnus glutinosa), ash willow (Salix atrocinerea), hazel (Corylus avellana), birch (Betula pendula) and dogwood (Cornus sanguinea). It usually occurs on soils with a certain structure, somewhat deep and with water reserves. It is located in several fragmented spots of great ecological value.
- Wetland areas: runoff water temporary accumulation areas. These areas usually have a more developed vegetation, typical of the alisedas (Hyperico androsaemi-Alno glutinosae sigmetum) geoserie. They function as strategic areas for local fauna and also serve an important function as an ecotone.
- Scrub-heath: areas at the property that are devoid of a significant tree stratum and in which predominate the thickets.
- Meadows and orchards: it brings together those areas in which herbaceous meadows predominate, often combined with small horticultural uses, of an autarchic nature. They are usually large and clear areas, lacking trees and shrub cover, which function as ecotone and passage areas for different faunal taxa.
- Rock habitat: in the active exploitation areas, the system of banks and berms originated during the exploitation stands out and that, once completed, have sufficient geomorphological stability due to the material hardness and offer different opportunities for the cracks fauna and flora due to the lower presence of operators and machinery.
The configuration and density of the different plant formations make the fauna observation and monitoring more complex than in other more open or less forested farms. The main groups present on the grounds of the factory and its farms are:
- Amphibians: present locally in areas with accumulation of runoff, prairie areas, etc. Pelophilax perezzi and Alytes obstetricans are easily detectable in wet areas. Around the farms, other amphibians not in the quarry can be detected, such as Salamandra salamandra, Triturus marmotatus or Lissotriton helveticus.
- Mammals: this group has an obvious but discreet presence, as they usually avoid daytime hours, especially in areas with productive activity, which is verifiable through footprints, traces and signals. Those that most evidence their activity are ungulates such as Sus scrofa or Capreolus capreolus, while the presence of carnivorous and mustelid mammals, such as Vulpes vulpes, Martes foina, Meles meles, or Mustela nivalis have a marked twilight character. The crossroads of plant covers, the rugged relief and the presence of bodies of water and buildings with cracks in the surrounding environment establish a hunting area for forest chiroptera and ubiquists such as Pipistrellus kuhlii, Nyctalus leisleri, Plecotus auritus and Pipistrellus pipistrellus.
- Birds: it is the group with the greatest presence and activity around the quarries and in the cement factory facilities. The forest character of the area favors the presence of raptors such as Buteo buteo, Pernis apivorus, Accipiter nisus and Accipiter gentilis, but especially highlights the usual nesting of a pair of Falco peregrinus in one of the abandoned quarry holes. Other birds with forest character and outstanding presence would be Pyrrhula pyrrhula, Dendrocopos major, Turdus philomelos, Garrulus glandarius, Regulus ignicapilla, Parus cristatus,etc. The rocky fronts and counters present activity of rock birds such as Falco tinnunculus, Ptyonoprogne rupestris, Phoenicurus ochruros, Corvus corax, Monticola solitarius, Pyrrhocorax pyrrhocorax and corvus corone. Other species with notable presence are Caprimulgus europaeus, Prunella modularis, Sylvia melanocephala and Ficedula hypoleuca.
- Reptiles: the mixture of rocky cutting areas and various forest and scrub covers offer opportunities for this group, especially for Podarcis muralis, Anguis fragilis, Coronella girondica and Lacerta schreiberi.
- Invertebrates: in addition to the remarkable presence of odonates and hemiptera, the set of soils has great potential for the group of pollinators, especially diurnal and nocturnal lepidoptera, which serve as an important trophic resource for other faunal groups. This area converges with the distribution areas of three invertebrates of interest: Lucanus cervus, Elona quimperiana and Austropotamobius italicus.
The cement factory and its quarries have a Biodiversity Management Plan since a few years, sampling, monitoring and modelling of specific habitats aimed at improving the ecological connectivity of the company owned lands with the habitats around.
Simultaneously with the works at the fronts, restoration projects are going on in certain points of the quarries.