by The conservation of large carnivores has historically been the subject of extensive debate due to the negative perception that exists towards these species as a consequence of the impacts they can have on society (damage to livestock, attacks on people, etc.). For this reason, they have been persecuted and have suffered a reduction in their populations in many parts of the world. However, this situation seems to have been reversed recently and some of its populations in Europe are recovering.
An example of this process is the Cantabrian brown bear. This population suffered a significant decline in the 20th century until it reached less than 100 individuals in the 1990s, separated into two subpopulations. From that moment on, conservation efforts increased with the preparation of recovery plans by the autonomous communities and, since then, the population has recovered and has come to have around 370 specimens, according to the last census. genetic.
Distribution changes
Trends in the number of she-bears with cubs showed that the minimum number of individuals was reached in the late 1980s. After that point, the population stabilized and began to recover, from 6 she-bears with cubs in 1989 to 38 in 2018.
Once this trend in abundance had been analysed, it was worth asking whether the same was happening with distribution. This is precisely what we analyzed in our recently published article in the journal Conservation Science and Practice.
In it, we analyze the changes in the distribution in three periods: 1982-1992, 1993-2002 and 2003-2012. These phases coincide with the demographic trends observed in the population. A first period that, according to abundance estimates, is a period of decline; a second period where the minimum is reached and stabilized and, finally, the third, which is a recovery period.
Our results reflect those trends in distribution. A small reduction in the distribution is observed between the first two periods, being the second period (1993-2002) where the minimum is reached in the surface occupied by bears. In the third period (2003-2012) a notable expansion of the distribution is observed, which increases by 70% compared to the second.
What territories does the bear colonize?
The territories (25 km² cells) colonized by bears vary depending on the quality of the habitat and the distance from the center of the bear population.
Thus, in the change between the second and third periods, bears mainly occupied areas with low human impact and that were closer to the center of the population than other available areas. Based on these results, it seems that the quality of natural habitat was not a limiting factor in this expansion.
Some previous studies show that more than 80% of the area with optimal habitat, both from the natural point of view and from human impact, were already occupied in the Cantabrian mountain range. These places are mainly the population centers where females with young live, who require a better quality of natural habitat.
Subadult males, which are the main dispersers in this species, are not as limited by natural habitat quality. Therefore, in a period of expansion, where they are mainly responsible for carrying it out, they occupied the territories with the least human impact.
Present and future of populations
Does the population continue to expand? The answer is yes. To analyze what could be happening in the population, we currently carry out a projection of the expansion model to predict the area occupied in the period 2013-2022.
The results showed that the area with a high probability of occupation for this period was almost double the area occupied in 2003-2012. To corroborate this, we compared the prediction with actual presence data collected between 2013-2021 and observed that 77% of the new areas predicted by the model had presence data for the species.
This corroborates that, especially in the western part, the population has continued to expand to territories far from the nucleus in the province of Ourense, the southwest of León and the north of Zamora, even further than the areas predicted in the model.
Outdated recovery plans
The recovery plans are the legal protection tools for the Cantabrian brown bear prepared by the autonomous communities at the beginning of the 1990s. The purpose was established to update said plans every five years based on the new needs of a population in continuous change. However, only Asturias updated its plan in 2002.
Since then, there has been no change in these plans and, instead, the population has undergone substantial changes in its distribution. In the study we compared the area of presence delimited by these recovery plans with the area of actual presence, and we found that the area delimited by the recovery plans covers only half of the area of presence of the population.
This situation could have implications for the present and the immediate future. On the one hand, the new areas of presence that are outside the area defined in the recovery plans are subject to less surveillance and control by the Administration and this could lead to an increase in mortality, complicating the establishment of the species in those areas.
In addition, to allow the expansion of the reproductive nuclei, a better state of conservation of the habitat seems necessary, which offers shelter and food to the reproductive females and allows them to establish themselves. For this it is necessary that the policies of conservation and improvement of the habitat referring to the bear are applied to the entire range of current presence and not only in the areas delimited by the plans.
Lastly, this lesser control by the Administration in the new areas of presence may also affect the management of damage caused by the species. In peripheral areas, less used to the presence of the bear, it is unlikely that beekeeping and livestock farms have preventive measures and, therefore, are susceptible to damage by the species. This can result in social discontent in areas not used to living with bears, generating a conflict and resulting in damage to conservation.
For all this, we consider updating the recovery plans a priority, adjusting the scope of their measures to the current situation of the Cantabrian population.
