Natural resource managers need tools that permit them to stratify their landscapes into various levels of risk, in order to apply a portfolio management approach to deploying treatments. This study presents the integration of three data types – 18m-resolution hyperspectral data acquired over four years of California’s drought for 26,000 km2 of California’s Sierra Nevada, outputs of the Basin Characterization Model, a hydroclimatic model that balances the water budget on a per-grid cell basis, and future climate models that bracket California’s future climate from + 2-4.5°C and +/-23% current mean precipitation by 2100.
We seek to determine what locations on the landscape are less climatically exposed using these three approaches, and ask whether these climate refugia seen in each approach overlap each other or not. We achieve this comparison by generating landscape maps Normalize Difference Water Index (NDWI), Climatic Water Deficit (CWD) and vegetation type-specific climate exposure. The then take the top quantile of each analysis to identify the areas that are the most exposed and the areas that are the least exposed. We overlay those to seek spatial congruence and identify the areas that present the highest confidence of being climate refugia.
Results/Conclusions
The hyperspectral analysis shows that during California’s recent drought over 85% of all measurable forest canopy dried out. Here, refugia are the areas of each vegetation type that dried the least. The BCM-approach reveals the locations containing the 10% lowest annual CWD, which can be stratified by vegetation type as well. Using future climate projections, the areas with the 10% least change in climate exposure from current time are the climate refugia. We present each result separately, and then show the combinations.
These three definitions of resilient locations on the landscape provide resource managers with more context for their landscape planning framework. For example, the canopy desiccation metric can perhaps be used to evaluate risk from future beetle outbreak, and to identify areas that are most in need of forest thinning. The BCM approach can help inform a landscape facet approach in which differential background rates of stress are used to help drive treatment strategies, and the future climate risks approach can help inform a wide variety of decisions, including what species to plant post-fire, and what areas may be suitable for preservation techniques, or will be so exposed that vegetation type transition may be a preferred option.