Serra d'Arga is the first major obstacle to wet winds from the Atlantic, with a maximum altitude of 825 meters. In this area, the climate is not very severe, although snowfall and periods of frost may occur at the highest points, presenting a temperate climate, typical of the Atlantic Biogeographical Region, with a wetter and colder period and a warmer and drier period in summer months.
This Special Conservation Zone is constituted by a mountainous massif, which is located between the valleys of Lima and Coura, and a flat area, which corresponds to a small river valley - river Âncora. At 800 meters of altitude, there is a plateau with several poorly drained depressions, where there are hygrophilic mosaics associated with wetlands, permanent water courses and temporary flooding areas.
In this SCZ, spontaneous forest is practically non-existent, being very difficult to distinguish it from forest plantations. In the riverside corridor of the Âncora river and in the land surrounding the agricultural land of the mountain villages, some native tree vegetation occurs.
Due to the fires and the few forest replacement actions in the region, exotic species, such as acacias, mimosas and the Hackea sericea shrub, have been proliferating in a significant and worrying way. However, the SCZ brings together conditions for potential regeneration, as well as a set of priority conservation biotopes and species contained in the Habitats Directive.
Recent studies on the region (intermunicipal project “From Serra d'Arga to Foz do Âncora”, NORTE-04-2114-FEDER-000227, 2019), indicate that 88% of the vascular flora taxons found correspond to indigenous plants, having been 32 RELAPE species (Rare, Endemic, Localized and Threatened or in Danger of Extinction) were found. These include the chupadeira-do-Minho (Scrophularia bourgaeana), a very rare Iberian endemism in Portugal, and Laserpitium prutenicum subsp. duriananum which, in Portugal, can only be found in Serra d’Arga.

The Serra de Arga Special Conservation Zone extends over 4493 hectares, of which 2154 hectares (about 48%) are within the boundary of the municipality of Viana do Castelo.

In this SCZ, there are 10 biotopes in Annex I of the Habitats Directive, 2 of which are considered priority: 4020* - Moist Atlantic wetlands of Erica ciliaris and Erica tetralix and 6230* - Herbaceous formations of Nardus, rich in species, in siliceous substrates of the mountain area (and continental Europe's sub-mountain areas)