Resistance and resilience through diversity

Millar, C.I., Stephenson, N.L. and Stephens, S.L., 2007. Climate change and forests of the future: managing in the face of uncertainty.

Written by Bethany Bradley, edited by Grace Gutierrez

Summary

We talk a lot in RISCC about adapting our management approaches to climate change.  Millar et al. (2007) is a ‘classic’ paper in climate adaptation that lays out approaches for helping forested ecosystems be more resistant to climate change or more resilient to climate change. Resistance means keeping the community the same while creating circumstances that make it less vulnerable to climate change. Reducing the prevalence of invasive species is one of the best examples of building climate resilience (e.g., Lopez et al. 2022) because it reduces compounding effects of multiple stressors. Resilience means enabling the community to change such that it can recover to the same or similar state when climate or other disturbances happen.  Millar et al. (2007) spend most of the paper discussing nine options for building resilience, which are outlined below in management implications. Underlying these recommendations is the important idea that diversity (of all sorts - species, age, genetic) builds resilience to climate change.  Moreover, Millar et al. (2007) were one of the first to recommend concepts of managed relocation - introducing warm-adapted species or genotypes into cooler climates - as a primary tool for building diversity and climate resilience.

Take home points

• Higher genetic, species, and age diversity creates climate resilience because it’s more likely that some individuals will be able to survive and thrive under future climate conditions.

• Managed relocations has been recommended practice in forestry for over two decades.

Management implications

Millar et al. (2007) outline nine approaches for building climate-resilient plant communities:

1. Assist species range shifts by planting species (e.g., in restoration treatments or for silviculture) outside of their historical ranges at the cold range margin.

2. Increase redundancy by opportunistically planting species within their historical ranges even if they weren’t there recently.

3. Broaden guidelines for genetic diversity to allow for the introduction of populations from warm-adapted sources (aka climate-adjusted provenancing).

4. In forests, build age diversity through thinning at early successional stages because individual trees might be vulnerable to different stressors at different points in their life.

5. Accept communities of plants outside of their historical ranges at the cold range margin (e.g., forest plots dominated by a novel, range-shifting species) rather than considering them as problematic or invasive.

6. Promote connected landscapes or stepping stones of conservation lands to increase the likelihood that species will shift their ranges on their own. 

7. In areas where there’s a clear direction to climate disturbance, restore with likely future conditions in mind (e.g., choose species better adapted to future climate).

8. Expect surprises and threshold responses to change and be prepared to respond to more disturbances.

9. Identify and support the conservation of refugia, which are areas buffered against climate change.

Related Papers

Prober et al. 2015; Gann et al. 2019; Pike & Haase 2024; Bucharova et al. 2016; Anderson & Wadgymar 2020; Woolridge et al. 2023; Hampe & Petit 2005

Keywords: Climate-smart restoration, assisted migration, assisted gene flow, climate adjusted provenancing, forest, managed relocation, plants, restoration