Individuals forced to look for more suitable habitat under climate change must contend with the extent to which humans have modified the surrounding landscape. (Credit: Pam Brophy)
Climate change will cause many species to shift their ranges. To do so successfully, individuals will need travel pathways that are hospitable to movement. These climate corridors – areas that form the best route between current climate types and where those climates will occur in the future under climate change – will be critical for species persistence.
The degree of climate connectivity in a landscape can be summed up by several types of measurements. For example, climate velocity estimates how fast organisms must travel in order to maintain similar climate conditions in future time periods. Climate exposure is a measure of the degree of dissimilarity in climate that individuals will encounter as they move in response to climate change.
One important factor influencing measures of climate connectivity is human land use, which is often not explicitly incorporated into climate assessments (if included at all). In the case of North America, only around 4% of the continent has no exposure to human land use, mostly in the northern latitudes. This means that exposure to human modified landscapes is ubiquitous, and needs to be included in any practical assessment of climate connectivity.
A new analysis does so by using climate projections in North America to predict the location of climate corridors both with and without the inclusion of human land use patterns, and comparing them quantitatively to see how they differed. These climate corridors were also measured to see how well they matched up with already existing protected areas.
Protected areas of the world, including those in North America that have the potential to represent climate corridors. (Credit: IUCN and UNEP-WCMC)
The results show that most climate assessments tend to underestimate both climate velocity and climate exposure when they don’t explicitly include human land use patterns. Climate exposure increased for 83% of the continent in models where human land use was incorporated versus those where it wasn’t. Although migrations northward are likely to be into less human-used regions, these regions are also likely to see increased human exposure in the future.
When looking at how well protected areas preserve climate corridors, there was a lot of regional variability. While the protected area network of North America as a whole does not represent climate corridors better than non-protected lands, some specific ecoregions do better than others. For example, the Great Plains and the Hudson Plain have poor representation of climate corridors, whereas the Arctic Cordillera and Tropical Wet Forests show better representation.
The take-home message is that it’s much more effective to incorporate human land use when thinking about climate shifts than to ignore it. Climate corridors, which represent the best pathways for succesful range shifts, also need to be well-protected for future use. Climate assessments are most useful when they incorporate multiple dynamic variables that represent barriers to movement. This ensures we have the best estimates of how biodiversity will shift over time.
Resources
Parks, S.A., Carroll, C., Dobrowski, S.Z. and Allred, B.W. 2020. Human land uses reduce climate connectivity across North America. Global Change Biology. DOI: 10.1111/GCB.15009.
Climate corridors of North America (August 2018)
Guidance for modeling and mapping climate-wise landscape connectivity (July 2018)
