**4. Discussion**

Habitat loss has been identified as a major factor negatively affecting biodiversity and threatening species conservation worldwide [13–15], but there is a need to study the impact of other large-scale factors such as mining. Here, we based our analyses assuming that habitat loss and habitat fragmentation affects the conservation status of the endemic species of amphibians and reptiles included in this study. We argue that it is more convenient for conservation purposes to impose a higher risk for a species due to habitat loss (even if this does not harm a species), than to leave the species under the same risk category under the assumption that habitat loss does not harm that species [19,52,53]. This argumen<sup>t</sup> is particularly important for endemic species showing small ranges of distribution.

Our results show that the combined negative impact of habitat loss and mining activities increased the loss of distribution of all species of amphibians and reptiles. For example, when considering only habitat loss, 49 species out of 179 species of amphibians and reptiles retained enough remnant natural habitat in their distribution, but 130 species lost more than 30% of their distributions, which could increase their vulnerability. When we added the combined impact of habitat loss and mining, all species distributions were reduced. Only 40 species showed less than 30% of habitat loss in their distributions, while 83 lost more than 30% of their distribution, 54 lost more than half of their potential distribution, and two species are in a critical situation where they only have less than 20% of their distribution remaining (Figure 1; Table S1).

Mining activities have become a relevant threat and could be causing species to increase their extinction risk. Of the 179 species included in our study, only 50 species (35 amphibians and 15 reptiles) are currently included in the IUCN red list of endangered species [4]. However, we believe that if other factors such as mining were systematically included into the assessment of species extinction risk, more species of amphibians and reptiles should be included in an extinction risk category. Furthermore, of the 179 species included in our study, 10 species have not been assessed by the IUCN or are under the data deficient (DD) category. When all of the species occurring in Mexico are considered, the number increases to over 38 amphibians (10% of all species in Mexico) in the DD category [19] and 307 reptiles (36.2% of all species in Mexico) in the DD or not evaluated (NE) categories [54]. Moreover, IUCN does not consider species of amphibians extinct in the wild, but some reports sugges<sup>t</sup> that at least 35 species are possibly extinct, and IUCN categorizes them as DD, EN, or CR [55,56]. Clearly, more e fforts are needed to improve the assessment of species of amphibians and reptiles given that many species have not been assigned with a proper risk category.

Our study only analyzed the impact of mining over species distributions, but other factors caused by mining activities, such as pollution of rivers and aquifers, polluting debris, acid drainage, gas and dust emissions, and local removal of all vegetation [28], could increase the impact of mining over species and further increase species extinction risks. It has been recently reported that 84 of the 632 highly contaminated sites in Mexico are caused by mining activities, of which 11 are found inside protected areas [57]. Therefore, further studies should focus on obtaining an integrated scenario of the impact of mining activities on biodiversity conservation. In Mexico, more than 20 million ha have concessions to carry out mining activities, and this area could double by the end of 2019 [29]. There is an increasing concern that current law regulations consider mining activities as a priority, to the point that they can even be established inside protected areas. In order to adequately conserve biodiversity and meet the international conservation commitments to conserve 17% of the territory and not to allow mining activities inside protected areas, the Mexican governmen<sup>t</sup> must urgently change sections of the environmental legislation.

Besides reducing species range size, habitat fragmentation has other implications on species conservation status. The configuration of the conservation area network solution ranked worst when including the combined impact of habitat loss and mining activities by increasing its area, perimeter, number of habitat fragments, and shape, with expected negative consequences for endemic and micro endemic species with dispersal limitations [58]. This increases risks of local population extirpation, and a decreasing genetic diversity of species [59]. Other factors, such as climate change, have also been considered to have a negative impact on species of amphibians and reptiles. It has been proposed that climate change will significantly increase the extinction risks in the short term. For example, it has been reported that an average reduction of about 64% in the current geographical range of endemic amphibians could be expected by the year 2080, with 50% of the species losing more than 60% of their distributions [60].

Protected areas are keystone initiatives to conserve biodiversity worldwide [61,62]. Thus, their adequate management, to ensure their long-term viability and to support the strategic development of conservation area networks, is essential [63,64]. Worldwide, these areas have helped to protect more than 2000 million ha [65] and in Mexico they protect around 25 million ha, representing more than 12% of the Mexican territory [66]. However, protected areas do not appear to adequately represent most biodiversity in Mexico, as shown by some studies using well-studied faunistic groups [16,63,67], and some biodiversity hotspots remain unprotected [67]. The population decline of species of amphibians and reptiles has been well documented, but these groups are not often taken into account when establishing conservation objectives [68,69]. Only 31% of the amphibians (29% of endemics) and 76% of the reptiles (46% of endemics) living in Mexico occur inside protected areas [70]. Furthermore, biodiversity representation in protected areas will be inadequate under current and climate change scenarios [71–73]. Our study provides baseline information suggesting that, as a result of the combined impact of habitat loss and mining activities, species of amphibians

and reptiles are in greater danger of extinction than previously known and these factors should be included in more integrated criteria for adequately assigning species conservation status.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/1424-2818/11/11/210/s1, Table S1: Percentage of distribution lost caused by the impact of habitat loss and habitat loss and mining activities for the Mexican endemic species of amphibians and reptiles.

**Author Contributions:** Conceptualization, F.M.-P. and F.B. methodology, S.C. and F.M.-P.; data analyses, S.C. and F.M.-P.; discussion and writing, F.M.-P., F.B., and V.S.-C.

**Funding:** F. Mayani-Parás was supported by a scholarship (Posgrado en Ciencias Biológicas of Universidad Nacional Autónoma de México and CONACyT (CVU 853134). This research was funded by the Instituto de Biología, Universidad Nacional Autónoma de México.

**Acknowledgments:** We thank the suggestions made by three reviewers that improved the quality of this manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.
