8.4. Climate change adaptation
While traditional natural resource management has tended to be ‘retrospective’—using knowledge of past and current conditions to inform today’s management actions—conservation professionals increasingly need to forecast future conditions. This forecasting is needed to determine the nature and magnitude of change likely to occur, and then translate that knowledge to current decision-making timeframes. Increasingly, it is no longer sufficient to assess “how is it doing?” and then decide what actions should be prioritized for the upcoming land use planning cycle. One must now ask “how is it changing, and by when?” and then translate that knowledge back into actions to take within one or more planning horizons.
While this re-orientation in natural resource management has become a requirement at installations with rapidly accelerating land use change, climate change now brings a globally pervasive stress on natural ecosystems. Temperature and precipitation regimes drive ecosystem productivity and natural dynamics, such as ocean temperature, seasonal streamflow, the rate of plant growth, and the frequency of natural wildfire. As the rate of climate change increases, substantial shifts in key ecological processes will cascade through local ecosystems, resulting in altered productivity, change in species composition, local extinctions, and many instances of ecological degradation or collapse (Barros et al. 2014). Therefore, in any given place, an assessment of climate change vulnerability for landscapes, ecosystems, and potentially at-risk species, is needed to forecast risk of ecological degradation or collapse. With this information in hand, managers can develop strategies for adaptation; that is management actions to reduce risk from continually changing conditions as they emerge over upcoming decades.
In their publication “Climate Adaptation for DoD Natural Resource Managers: a Guide to Incorporating Climate Considerations into Integrated Natural Resource Management Plans” Stein et al. (2019) detail a 6-step process for addressing these challenges.
1. Set context for adaptation planning
2. Assess climate vulnerabilities and risks
3. Evaluate implications for INRMP goals and objectives
4. Develop strategies and actions to reduce climate risks
5. Implement adaptation actions and projects 6. Monitor and adjust adaptation actions
Here we introduce aspects of steps 2 (vulnerability assessment) and 4 (adaptation strategies) as related to landscapes and ecosystem management by DoD.
Climate change vulnerability assessment
Climate change vulnerability is commonly defined as “the degree to which a system is susceptible to, or unable to cope with, adverse effects of climate change, including climate variability and extremes” (IPCC 2007). Vulnerability assessments tend to include a series of measurements to quantify climate change exposure, sensitivity, and adaptive capacity. In the context of conserving natural resources, these terms can be defined as
- Exposure – is the degree to which the target resource might be subjected to the change in conditions;
- Sensitivity – the degree to which the target resource being assessed might be affected by climate exposure, including interactions of climate stress with other kinds of stress;
- Adaptive Capacity – the ability of the target resource to adjust to, and cope with, changing conditions.
Vulnerability assessments address different levels of ecological organization, such as species, local ecosystems, or landscapes. The species level is the most common focus for vulnerability assessment and consequently has received extensive attention in the scientific literature (Rowland et al. 2008, Pacifici et al. 2015). These approaches examine projected climate change where the species occurs, aspects of the genetic variation, natural history, physiology, and landscape context to assess sensitivity and adaptive capacity (Foden et al. 2018). Assessments of landscapes often produce mapped results for interpretation at regional scales. Evaluation of climate exposure may result in maps showing where climate-induced stress is indicated to be greatest, whereas examination of the potential climate-change effects on disturbance regimes or invasive species can address aspects of sensitivity (Swanston et al. 2010, Rustad et al. 2012). Adaptive capacity can be measured through examination of the heterogeneity of topography, moisture gradients, or microclimates under the assumption that more diverse landscapes provide more opportunities for organisms to find climate refugia than homogeneous ones (Hamman et al. 2015).
Assessing the vulnerability of local ecosystems provides a useful complement to both landscape and species assessments. Whereas landscape assessments indicate a high potential for regional climate-change impacts, analysis of component ecosystems aims to more directly measure how climate change will impact species assemblages, ecological processes, structure and function, and is a next logical step to identify practical adaptation strategies (Finch et al. 2012).
In one example, NatureServe developed a framework for assessing climate change vulnerability in local ecosystems and habitats. Using the framework, ecologists treated predominant upland vegetation types, such as warm desert scrub, sagebrush steppe, pinyon-juniper woodlands, and mixed conifer or aspen forests extending from low to upper montane elevations over 3.2 million km2 of Western North America.
The framework addressed climate exposure and ecosystem resilience; the latter derived from analyses of ecosystem sensitivity and adaptive capacity (Figure 8.7).
Measures of climate change exposure used observed climate change (1981–2014) and then climate projections for the mid-21st century (2040–2069 RCP 4.5).
Measures of resilience included (under ecosystem sensitivity) landscape intactness, invasive species, fire regime alteration, and forest insect and disease risk, and (under adaptive capacity), measures for topo-climate variability, diversity within functional species groups, and vulnerability of any keystone species.
As of 2014, moderate climate change vulnerability was indicated for >50% of the area of 50 of 52 types. By the mid-21st century, all but 19 types will face high or very high vulnerability with >50% of the area scoring in these categories. Measures for resilience explain most components of vulnerability as of 2014, with most targeted vegetation scoring low in adaptive capacity measures and variably for specific sensitivity measures. Elevated climate exposure explains increases in vulnerability between the current and mid-century time periods (Comer et al. 2019).
Climate change adaptation
For DoD purposes, climate adaptation is defined as “adjustment in natural or human systems in anticipation of or response to a changing environment in a way that effectively uses beneficial opportunities or reduces negative effects” (DoDD 4715.21). More generally, adaptation actions are intended to reduce climate-related vulnerabilities or enhance resilience. Indeed, adaptation planning can be viewed as a process of iterative risk management.
Given the wide array of natural resource–related programs and activities addressed in INRMPs, it is challenging to provide guidance on specific strategies that might be appropriate to consider in any instance. For example, Swanston et al. (2016) offer one set of high-level strategies from a forestry perspective
- Sustain fundamental ecological functions
- Reduce the impact of biological stressors
- Reduce the risk and long-term impacts of severe disturbances
- Maintain or create refugia
- Maintain and enhance species and structural diversity
- Increase ecosystem redundancy across the landscape
- Promote landscape connectivity
- Maintain and enhance genetic diversity
- Facilitate community adjustments through species transitions
- Realign ecosystems after disturbance
Results of NatureServe’s analysis of western vegetation types suggest adaptation strategies that suit the character of each type, or groups of ecologically similar types. For example, warm desert shrublands and semi-desert grassland types already score in the high vulnerability range. It would be prudent for planners and managers to evaluate current landscape patterns and identify zones where they can anticipate plant invasions from neighboring vegetation (Bachelet et al. 2016). Where degraded from prior land uses, restoration of native herb diversity and nitrogen fixing taxa are also needed. Monitoring for pollinator population trends, invasive plant expansion, and shrub regeneration, are also increasingly urgent.
Further north and upslope, pinyon-juniper woodlands currently tend to score in the low-moderate range of vulnerability, but by mid-century, they score in the moderate to high range of vulnerability. Actions to maintain or restore resilience in these forests are needed. These could include protection of remaining “old growth” stands while restoring natural wildfire regimes and tree canopy densities in the surrounding areas.
Over the coming decades, as temperature and precipitation patterns change, models of wildfire regimes will need to be updated and customized to local conditions. Monitoring for invasive plant expansion, effects of drought stress, and tree regeneration will all increase in urgency. Looking out towards the mid-21st century, nearly all types assessed here would benefit from a set of resilience-based strategies, so these investments in the near-term may limit needs for more extreme measures later in the century.