Over the last few decades, temperature has increased in the Arctic which has been linked to an increase in productivity (Elmendorf et al. 2012). Myers-Smith et al. (2011) reported that willow species that form canopy structure are increasing and expanding on Hershel Island Territorial Park. These changes in vegetation structure and distribution will have significant effect on the ability of northern people to harvest country-food and for wildlife sufficient habitat. Both Myers-Smith et al. (2011) and Elmendorf et al. (2012) identify that evidence for increased productivity and shrubification have been limited to ground-plots or airphoto interpretation that are not geographically diverse. The term "shrubification" in this context occurs when shrubby species increase in abundance, physiognomy or invade areas not previously occupied by the species. Myers-Smith et al. (2015) proposed that climate-shrub growth relationships characterized for climatically variable geographic areas could be used to improve how vegetation response to climate change is interpreted in future projections.
The influence of climate change on ecological processes can be achieved through bioclimate envelope models, or process-based mechanistic models. Mechanistic models simulate ecological processes but require rich data sources. Bioclimate envelope models can generally provide projections about ecosystem change more quickly than process-based models but rely on reasonably accurate ecosystem/land classification. A bioclimate envelope describes the climatic variables that drive contemporary (modern day) ecosystem development within a particular landscape. A bioclimatic envelope approach to assess ecological change has not been done for arctic regions. Others however, have used bioclimate envelopes to study boreal ecosystem response to climate change (Fettig et al. 2013; Mahony et al 2017; Mbogga et al 2010; Rehfeldt et al 2012; Wang et al 2012).
Bioclimate envelope models project the distribution of climatically suitable ecosystems in novel landscapes. A conceptual model of this idea is presented in Figure 1. In this conceptual model, I use two climate variables to illustrate how a bioclimate envelope can be used to interpret ecological vulnerability. Ecosystems, whose future climate shifts only a little, are less vulnerable; those that shift without any overlap with the contemporary climate are more vulnerable. Those ecosystems that shift within the envelope of a contemporary ecosystem are still vulnerable but the shifted climate is not novel. In some cases the shift in the envelope is so extreme there is no contemporary, it is a completely novel climate in the landscape. Interpretation of projected bioclimate envelopes will provide guidance to land managers in dealing with ecosystem changes to know which system may change and how they might change.
A bioclimatic ecosystem classification provides a fundamental tool to create projections of future ecosystem changes specific to Yukon’s arctic region from the broad to local scale. An ecosystem-vulnerability map can also provide a consistent way to integrate findings of climate change research.
Figure 1. Conceptual model to assess ecosystem vulnerability using a bioclimate envelope approach.