Protected areas (PAs) are the main global policy instrument to avert the current biodiversity crisis by conserving
important species and habitats on site. Yet important pressures around PAs and in PAs, notably land use-land
cover (LULC) changes, jeopardise the conservation role of these tools. In Spain, as well as in most developed
countries, land development is the main pressure on its rich biodiversity. Here, we used a semi-experimental
Before-After-Control-Impact (BACI) research design with covariates to ascertain whether three categories of
multiple-use PAs including Nature Parks, Sites of Community Importance (SCIs) and Special Protection Areas
(SPAs) have been effective to prevent land development in Atlantic Spain between 1987 and 2017 using CORINE
Land Cover (CLC) data. We split our census sample of PAs according to two geographic zones: coastal zone and
inland zone, and four administrative sub-zones (regions with distinctive governance systems): Galicia, Asturias,
Cantabria and the Basque Country. We created and tested the validity of three types of controls specific to each
PA category: standard 5-km buffer controls, bio-physically adjusted standard controls, and bio-physically
adjusted random controls across zones. Multiple-use PAs reduced, though not completely avoided, land development
in all zones and sub-zones compared with controls. An effectiveness gradient among PA categories was
apparent: NPs ≥ SCIs > SPAs. Coastal areas, both protected and unprotected, experienced greater land development
rates than inland areas, with coastal SPAs showing poor effectiveness results. The Basque Country was
the best-performing region regarding PA effectiveness, with the remaining regions showing similar PA performance
results regardless of the prevailing political party in power for most of the study period. Random controls
had the greatest bio-physical similarity to their cases and produced larger control areas than standard buffer
controls.
