Assessment of the National Park network of mainland Spain by the Insecurity Index of vertebrate species

The evaluation of protected area networks on their capacity to preserve species distributions is a key topic in conservation biology. There are different types of protected areas, with National Parks those with highest level of protection. National Parks can be declared attending to many ecological features that include the presence of certain animal species. Here, we selected 37 vertebrate species that were highlighted as having relevant natural value for at least one of the 10 National Parks of mainland Spain. We modelled species distributions with the favourability function, and applied the Insecurity Index to detect the degree of protection of favourable areas for each species. Two metrics of Insecurity Index were defined for each species: the Insecurity Index in each of the cells, and the Overall Insecurity Index of a species. The former allows the identification of insecure areas for each species that can be used to establish spatial conservation priorities. The latter gives a value of Insecurity for each species, which we used to calculate the Representativeness of favourable areas for the species in the network. As expected, due to the limited extension of the National Park network, all species have high values of Insecurity; i.e., just a narrow proportion of their favourable areas are covered by a National Park. However, the majority of species favourable areas are well represented in the network, i.e., the percentage of favourable areas covered by the National Park network is higher than the percentage of mainland Spain covered by the network (result also supported by a randomization approach). Even if a reserve network only covers a low percentage of a country, the Overall Insecurity Index allows an objective assessment of its capacity to represent species. Beyond the results presented here, the Insecurity Index has the potential to be extrapolated to other areas and to cover a wide range of species.

评估保护区网络维持物种分布的能力，是保护生物学（conservation biology）领域的核心议题之一。保护区类型多样，其中国家公园（National Parks）的保护等级最高。国家公园的设立可依据多种生态特征，其中包括特定动物物种的存在情况。本研究选取了37种脊椎动物（vertebrate），这些物种因具备重要自然价值，至少被西班牙本土的10座国家公园中的一座列为重点保护对象。我们采用适宜度函数（favourability function）对物种分布进行建模，并运用不安全指数（Insecurity Index）测算各物种适宜生境的保护程度。针对每个物种，我们定义了两类不安全指数指标：单栅格单元不安全指数，以及物种整体不安全指数。前者可识别针对各物种的不安全生境，用于制定空间保护优先级策略；后者为每个物种赋予一个不安全指数值，我们利用该值计算物种适宜生境在保护区网络中的代表性。正如预期，由于国家公园网络的面积范围有限，所有物种的不安全指数均处于较高水平，换言之，仅有极小比例的物种适宜生境得到了国家公园的覆盖保护。但多数物种的适宜生境在网络中均得到了良好的代表性覆盖，即国家公园网络覆盖的适宜生境占比，高于该网络覆盖西班牙本土陆地面积的占比（该结果同样通过随机化方法得到验证）。即便保护区网络仅覆盖一国极小比例的陆地面积，整体不安全指数仍可客观评估其代表物种的能力。除本研究所得结果外，不安全指数还具备被推广至其他区域、适用于更多类群物种的潜力。