Strengths of the protocol
The MIREN road survey protocol is unique for its focus on two critical co-occurring global change drivers on biodiversity and species redistributions in mountains: climate change and road construction (Figure 5). Road construction represents one of the most prominent and increasing land-use changes in many remote regions (Meijer et al., 2018), leading to physical disturbance, dispersal corridors and vectors for plant species (Gelbard & Belnap, 2003). Coupled with this, elevation gradients are good proxies for temperature and can be used as space-for-time model systems for simulating climate change-induced temperature increase, where low elevation systems to a certain extent represent future scenarios for higher elevations in a warming climate (Blois et al., 2013; Lembrechts et al., 2017). Given this, combining elevation-based climate gradients with road effects allows researchers to disentangle the interactive effects of climate and road construction – as an example of human land-use change – on biodiversity, including their relative importance as drivers of species redistributions. Indeed, it is along clear linear dispersal pathways like roads that changes in species distributions – and especially those of non-native species – become apparent (Lembrechts et al., 2017). This is particularly relevant when considering the repeated survey approach of the MIREN design, which makes it possible to study the temporal dynamics of plant species distributions in response to natural (e.g. succession after natural disturbances, such as fire), as well as anthropogenic disturbances (e.g. land-use changes, such as increasing urbanization or domestic grazing, or the introduction of non-native species).
A final advantage is that along each road, sites are selected at predetermined elevations and capture all habitats found along an elevation gradient, equally covering all elevational belts. The protocol provides a methodological standardization that is straightforward to replicate globally and yet still yields sufficient explanatory power for regional case studies due to due to its relationship to the elevation gradient and its within-region replication (i.e. sampling along three mountain roads in each region; e.g. Arévalo et al., 2010; Pollnac et al., 2012). In doing so, the protocol remains simple, for example with plots close to roads remaining easy to reach, and thus applicable in many mountain regions even when fieldwork sites need to be easily accessible. This provides another strength of the protocol: it can be repeated in many places, so that general patterns at the global scale can be detected through multi-region replication (Alexander et al., 2011; Seipel et al., 2012; Lembrechts et al., 2017). In summary, data collected within the MIREN survey framework can be useful for regional and global studies in a large variety of fields, ranging from classical biogeography and community ecology to ecological modelling and global change research.