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The main cause of biodiversity loss in the industrialised countries is the process of urban development and land occupation, which affects the connectivity of ecosystems and causes natural habitats to become fragmented and isolated.

As established in the Plan for Spaces of Natural Interest (PEIN, 1992), one of the main objectives of landscape ecology is to prevent the formation of a series of isolated green patches.

Due to the density of the urban fabric and infrastructure systems that surround the Serra, Collserola Park is currently undergoing a process of ecological isolation from other natural spaces. For years, work has been devoted to ensuring ecological connectivity with such spaces and to establish appropriate corridors between protected areas. To this end, a priority is to connect Collserola with Sant Llorenç del Munt i l’Obac Natural Park on the Vallès side. Other connections are also necessary with such other natural spaces in Barcelona Metropolitan Area as the Serralada de Marina and Garraf parks.


Ecological connectivity and isolation

Biological connectivity concerns the possibility that species have to move around, disperse, migrate or colonise, allowing them to settle in other places and exchange genetic information.

Looking at the map, we can quickly see the difficulty of achieving ecological connection amongst natural spaces in Barcelona Metropolitan Area due to urban development and existing and planned infrastructure.

If the areas on the outskirts of natural spaces are correctly conserved, they act as zones of influence that buffer the impact generated by urban areas and road infrastructure. For this reason, from the management standpoint, it is vital that we remember the importance of conserving such peripheral zones adjoining the Park, precisely since these can decrease impact and mark the beginning of ecological corridors. Such areas are directly involved in ecological processes, the flow of energy, materials and organisms.

It is in what remains of the cultivated land on the Vallès county side of the Park that we find the most important demonstration exercised by these zones of influence. It is here, therefore, that we should prioritise uses that are compatible with conservation of the Park and which also enable us to advance towards the great challenge of connectivity with Sant Llorenç del Munt i l’Obac Natural Park.

Spaces reserved as connectors can perform different roles according to their width, quality as habitat and the requirements of the species. We should make a clear distinction between a corridor large enough to provide a habitat for various animal species and a crossing place provided so that fauna can overcome a particular obstacle, such as road infrastructure.

In recent years, a clear need has emerged to include environmental criteria in those governing clear landscape in town and country planning in order to promote strategies aimed at increasing the permeability of the urban fabric. The goal is to conserve and increase biodiversity and to prevent the Serra from becoming dangerously isolated.


Fragmentation of the territory

As land is occupied and transformed, it is divided into different parts that are non-communicated with each other in the biological sphere. This is the process that we call the fragmentation of habitats. By habitat, we mean the territory that an animal requires in order to find the food and shelter necessary to live and reproduce, that is, to develop its life cycle. One of the features that most contributes to fragmentation of this territory is transport infrastructure.

We refer only to the roads that cross through the interior of the Park. Depending on the nature of the road infrastructure and the territorial needs of a particular species, fragmentation can completely destroy the connection between one side of the road and the other. This may be a physical barrier, due to the difficulties in crossing, or a behavioural obstacle, generating the tendency to avoid the barrier. How difficult it is to overcome such an obstacle depends, in each case, on the ecology of the species involved and the characteristics of the barrier.

Incidents involving fauna on the Collserola roads have been monitored in order to study different factors relating to the risk of accident. The results show that mammals are the group with the highest number of deaths by being run over. The species most affected are hedgehog, squirrels, common rabbit, wild boar and genet.

Consorci del Parc Natural de la Serra de Collserola
Ctra. de l'Església, 92. 08017 Barcelona. T: 932 803 552


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