External limitations
Application of the MIREN road survey protocol might be hindered in some regions, most obviously due to the lack of roads spanning sufficiently large elevation gradients. Additionally, local land ownership, safety issues or administrative complexities may complicate establishment and monitoring, for example on private land or in protected areas (Figure 5). Such issues might be of particular relevance in the MIREN survey design, as MIREN strives to cover a large elevation gradient spanning multiple vegetation zones. At the same time, the proximity of survey plots to roads increases the risk of damage over time (e.g. through road widening, mowing, pesticide use, expanding urbanization or occasional vandalism). The simplicity of the plot set-up nevertheless greatly reduces the impact of such damage or vandalism in the long term.
Long-term monitoring itself comes at a risk of funding insecurities, as the timeframe of 5-year intervals is beyond what is covered by most grants. Even though maintaining the observational sites themselves comes at virtually no financial cost, the monitoring involves considerable input of field labour, for which costs will vary between regions (Figure 5).