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.