A scientific team led by the Doñana Biological Station – CSIC has estimated that the distribution of the wolf in the mid 19th century was, at least, 65% of the territory of the Iberian Peninsula. To arrive at these conclusions, the researchers have reviewed the geographical dictionary edited by Pascual Mendoza in the mid-19^th century, which described every population centre and topographical elements in Spain. The study has been carried out with the collaboration of the German Centre for Integrative Biodiversity Research – iDiv and has been published in the journal Animal Conservation.

Human beings are both witnesses and drivers of the biodiversity lost in the planet. The population of many species are increasingly lower, even disappearing from many places. "The knowledge we have about these declines comes from the comparation between indexes that describe the distribution and abundance of species across time", explained Miguel Clavero, researcher at the Doñana Biological Station – CSIC and main author of the study. "However, the data needed to calculate these indexes have started to be taken just recently, in the last decades, while human activities have been causing impacts during centuries". For this reason, the awareness on the recent declines can be just a miniature of real declines. "Even the supposed ‘expansion' of some species may be just an illusion, result of looking through a very limited time window, as it is happing with the wolf currently", he added.

Wolves were present in all provinces

The geographical dictionary edited by Pascual Madoz in the mid-19th century is the result of a great collective effort, with more than 1400 participants, to describe every population centre and topographical element in Spain. Among the included elements in the descriptions, we can often find wild species, mainly those ones perceived as useful (hunting or fishing targets) or harmful (wolf and other carnivores). The researchers reviewed the 16 volumes and more than 11000 pages of the dictionary to compile and locate on the map more than 1500 mentions of wolves, distributed across all mainland provinces.

According to Néstor Fernández, researcher at the iDiv in Germany and coauthor of the study, "this information is interesting, but we can not directly take the historical distribution of the wolf from it, as other works did. Madoz's dictionary doesn't provide any information of fauna from many places in Spain and we can not take the lack of mention for absence". To give a solution to this problem, they also compiled and located more than 5200 mentions to other species of land fauna species, considering those places with mentions of other wild species but not the wolf, as areas with a possible absence of wolves.

The scientists combined the compilation of population centres with and without wolves taken from Madoz's dictionary with different values that describe environmental and human population values to estimate the distribution of the wolf in the mid-19^th century in Spain with statistics models. "These models allow us to estimate the probability of wolves to be present on areas of which Madoz's dictionary doesn't provide any information", pointed Néstor Fernández.

The results show that the presence of wolves was less frequent in flatter areas, more suitable for agriculture and with higher human population density. In a conservative way, the species occupied more than 317,000 km2, that is, more than 65% of the territory of the Iberian Peninsula. According to Miguel Clavero, "this estimation must be taken as a minimum value, since the reliability of the presences of wolves identified in the dictionary was higher than the absences. The area with presence of the species in the mid-19^th century was higher for sure".

The current ‘expansion' of the wolf

Comparing the current situation with the historical distribution, the present area of wolf occurrence is only 30% of what it was in the mid-19^th century. Introducing this long-term perspective, "the supposed expansion of the species in the last years would be only an stabilization of the severe decline of the wolf", says the researcher. An authentic recovery of the species and its important ecological functions would imply its return to the areas of historical presence beyond the northwestern Spain. This horizon brings numerous challenges for the coexistence between humans and wolves, especially in those places where the presence of this species is no longer part of the collective memory.

The recently published study shows the potential of the historical sources to know the natural environment and inform the administrations. The correct use of these sources needs a great and careful effort and requires the application of statistic technics to correct the gaps and information bias that historical documents have. "This effort is worthy if we can widen our temporary horizons in which we evaluate the status and trends of ecosystems and species", concluded Miguel Clavero.

Reference:

Clavero, M., García-Reyes, A., Fernández-Gil, A., Revilla, E., Fernández, N. (2022) Where wolves were: setting historical baselines for wolf recovery in Spain. Animal Conservation. https://doi.org/10.1111/acv.12814

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