Whilst rambling through the valley you will be able to learn about this Mediterranean forest and its inhabitants. Ever since the Middle Ages, people have sustained their living on the 'Riera de Merlès' area, as can be seen by the flour mills, farmhouses and gullies (where witches used to gather back in the 17th century), as well as the medieval churches of Sant Esteve de Comià, Sant Martí de Boatella and Santa Maria de Salselles.

In the Riera de Merlès' Nature Reserve you can find fish such as trout, barbels and catfish, as well as amphibians such as Pyrenean newts, salamanders and frogs. There are also reptiles, including adders, green and common lizards, small Mediterranean lizards, and a number of snakes (green, white, plain and water snakes) and water birds, mainly dippers and kingfishers. Other birds of interest include honey-buzzards, black woodpeckers and woodcocks. Golden eagles and peregrine falcons are known to nest on the nearby Cingles del Catllaràs' cliffs. Capercaillie (Tetrao urogallus) can also be spotted locally. Crayfish and Spanish Moon Moth (Graellsia isabellae ) are also of special significance.

Plants of a typical Pre-Pyrenean flora such as rosemary, thyme, white oak and Scotch pine, are particularly abundant.

The Riera de Merlès is a tributary of the River Llobregat, draining into the vicinity of Puig-reig and Gaià. The average annual rainfall is 880 mm, the river has a catchment area of 173 sq Km, with an average flow of 0.90 m3/s, approx. and a total length of 19.5 Km. It follows a typical mountain river pluvionival regime, similar to that of the Alt Llobregat. The area enjoys a special protection status that covers water abstractions, fishing and any other activity which could have a detrimental effect on the delicate river environment.