Abstract
In the Sierra de Guadarrama National Park (central Spain), the population of Iberian wild goat, also known as Spanish ibex (Capra pyrenaica) has grown strongly since its reintroduction three decades ago. The plant community is now under heavy browsing pressure due to this high population. A study of the presence of moss on rocks was used herein as the basis for the design of an indicator, named impact on mosses (im), to describe the environmental pressure exerted by the Iberian wild goat in terms of moss removal. Granite and gneiss zones at medium altitudes with continental Mediterranean climate are the most suitable areas for successful application of the indicator. The hypotheses to test are: (1) the indicator will discriminate between areas with different wild goat pressure levels, (2) wild goat pressure will explain a high proportion of moss loss variance, and (3) the im indicator will be useful to establish a mathematical model between wild goat pressure and moss loss. The proposed indicator was analyzed using both statistical and data science techniques. The results support the mentioned hypotheses. Specifically, statistically significant differences were found regarding the impact on mosses between areas with different levels of Iberian wild goat pressure. Thus, a high proportion of the variance was associated with wild goat pressure (80% for high-pressure areas, 56% for low-pressure areas). A modified parabolic function was fit to express the relationship between Iberian wild goat pressure and impact on mosses. In conclusion, the im indicator was shown to be a useful tool to assess pressure due to Iberian wild goat. Therefore, im can help assess and manage Iberian wild goat populations and determine their sustainable levels.
Highlights
For more than 30 years, the Iberian wild goat has been part of the Sierra de Guadarrama landscape
The present study focuses on an area with low water availability to check for a possible negative relationship between the abundance of Iberian wild goat and moss cover on rocks
Over the last 25 years, large areas of the Sierra de Guadarrama have suffered from serious erosion problems (GarcíaRodríguez 2015, 2018). This is caused by natural processes, anthropic activities related to the management of protected areas, mass sporting activities, and overgrazing and/or trampling by the Iberian wild goat and other livestock species (PNSG 2020)
Summary
For more than 30 years, the Iberian wild goat has been part of the Sierra de Guadarrama landscape. The constant pressure exerted on the environment since their reintroduction has produced significant damage on woody plants (Perea et al 2015), mosses, and soils. This results in an unbalanced and unsustainable relation (García-Rodríguez 2018). The impact of wild ungulates on moss cover was found to be nonsignificant in environments with greater water availability and plant cover (Marozas et al 2009). The present study focuses on an area with low water availability to check for a possible negative relationship between the abundance of Iberian wild goat and moss cover on rocks. As wild goats have excellent rock-climbing skills, their impact on moss cover may be related to trampling and rock erosion
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