The establishment of protected areas is one of the main tools used for biodiversity conservation, one of the components of environmental management. Although the theoretical framework for protected areas has been long known and discussed, there are few data about their practical effectiveness as a means to preserve biodiversity. Through the analysis of information from the Global Biodiversity Information Facility (GBIF), we have looked for any relationship between the protection status and the general species richness (i.e., number of all living species, taken as a surrogate for biodiversity) in the Spanish Pyrenees. We found that higher protection levels were associated to higher richness of non-endangered species. However, additional reliability tests have shown that for endangered species, the amount of currently available data may still be insufficient for effective management. To avoid this lack of reliability, enhancing public access to biodiversity data or improving sampling effort is mandatory.