Veinte años de cambio: evolución del hábitat y de la comunidad de caracoles en el Parque natural de la sierra de Collserola (2003–2023)

Abstract

Soil fauna plays a fundamental role in the viability and functioning of ecosystems. In

particular, terrestrial snails contribute significantly to the maintenance of biodiversity through

the decomposition of organic matter and the recycling of nutrients. Their limited mobility

makes them highly sensitive to environmental changes, positioning them as excellent

bioindicators of habitat alteration.

The main objective of this study is to assess and determine how environmental changes

occurring over a 20-year period, between 2003 and 2023, influence the species richness and

relative abundance of mollusk communities established in the Collserola Natural Park

(Barcelona, NE Iberian Peninsula).

To this end, soil and snail samples were collected from 108 localities previously established

during the 2003 study, within the perimeter of the protected area. The collected specimens

were identified in the laboratory: larger individuals by direct observation and smaller ones

using binocular microscopes. In parallel, indices of vegetation productivity (NDVI and EVI),

changes in vegetation type and land use, as well as the minimum distances between

sampling sites and nearby ecotones were calculated. Canonical correspondence analysis

(CCA) and generalized linear models (GLMs) were then applied to explore the relationships

between these environmental variables and the malacofaunal community.

The results reveal a strong relationship between vegetation cover and terrestrial snail

populations. In particular, the loss of landscape heterogeneity, mainly due to reforestation

and the abandonment of open areas, is driving ecological homogenization, which is

associated with a reduction in gastropod species richness. Additionally, habitat humidity was

identified as a critical and limiting factor for mollusk populations.

The current trend toward afforestation and more mature ecological stages threatens the

viability of numerous terrestrial snail species associated with open or transitional habitats

(including several endemisms). To preserve mollusk diversity, it is advisable to maintain the

characteristic habitat mosaic of Collserola Park and ensure a balanced distribution of

ecological zone

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