TOPOCLIMATE REFUGIA

[PUBLICATION] Topoclimates, refugia, and biotic responses to climate change

Figure showing an aerial view of Pepperwood Preserve

Overview

This research, published in Frontiers in Ecology and the Environment (2020), examines how topography and climate interact to shape plant distributions and their vulnerability to climate change. As a co-author on this paper led by David Ackerly, I developed the analytical approach and statistical models for testing the “hydroclimatic compensation model” (Figure 4), which shows how tree species distributions shift from south-facing to north-facing slopes as they approach the warm edge of their climatic range.

Research Questions

The study addressed three key questions:

Do species shift their topographic distributions at the edges of their geographic ranges, preferring north-facing slopes in warmer/drier regions and south-facing slopes in cooler/moister regions?
Within a landscape, do species found on cooler microsites tend to have cooler geographic distributions overall?
Are species occupying cooler landscape positions more vulnerable to climate warming?

Key Findings

Our results indicate that:

Species shift across the topographic gradient as they approach their climatic limits, with populations restricted to cooler, north-facing slopes at the warm/dry edge of their range and restricted to warmer, south-facing slopes at cool/wet range edges.
Within a single community, species occupying cooler microsites tend to have cooler geographic distributions overall
Species found on north-facing slopes and valley bottoms are projected to experience greater population declines under climate change scenarios with increased water deficit

Implications

These findings have important implications for conservation in the face of climate change. Contrary to some assumptions, cool microsites that are often viewed as potential climate refugia may actually harbor species that are most threatened by further warming, as these are often populations at the edge of their climatic tolerance. This understanding can help guide “climate-smart” conservation strategies that account for both regional and local climate patterns.