Dear Adaptation Mavens,

I’m a little confused. I read Scanning the Conservation Horizon, which said that possible vulnerability assessment targets include ecosystems, species, and habitats. Then I went to a vulnerability assessment training, and one of the instructors made some comment about doing a vulnerability assesessment on management measures or even laws and policies. I could see how you could do a vulnerability assessment on non-biological targets like infrastructure that have a real, physical presence, but how the heck do you apply concepts like exposure, sensitivity, and adaptive capacity to a management measure or a law?

Conceptually Challenged Assessor

Dear Assessor,

Great question. So often we all get stuck in our own view of the world, and taking a new perspective can make a familiar issue look completely foreign. The truth is, the concept of assessing vulnerability has been around for a long time, and has been employed by all kinds of people for all kinds of problems.

But let’s break this down a little. In the world of climate change vulnerability assessments (VAs), exposure refers to how much change the assessment target will experience regardless of what effect those changes might have. It includes climatic changes like altered temperature or precipitation, but can also include so-called second-order changes that occur as a result of climatic changes. This might include, for example, changes in vegetation type or fire regime. It sounds like you’ve got a handle on how to think about various elements of exposure for biological and other physical targets, so let’s focus on how you might think about the exposure of a management measure or a policy to climatic changes and effects.  

Let’s consider a pretty obvious example: water allocation. In the case of lakes, rivers, or other water sources influenced by precipitation and evaporation, the resource being allocated and thus the policy regulating it is subject to both interannual variability as a result of short-term climate cycles like El Niño or the Pacific Decadal Oscillation, and long-term changes related to long-term climatic change. In those cases exposure to change could easily be high. If the water being allocated is from a deep aquifer, its exposure to changes in precipitation or temperature would likely be low.

What about sensitivity? This refers to the effect of any changes that happen on your assessment target. People often confuse sensitivity and exposure, but it’s worth keeping them separate. For species that are exquisitely sensitive to changes in temperature even a low exposure (i.e. a small change) could result in high overall vulnerability. For species that are completely insensitive to temperature, even a high exposure (i.e. a large change) might not translate into high overall vulnerability.

Stein's Sunburn Analogy for VAs: sensitivity = how much you burn or tan when you spend time in the sun

Now back to our water allocation example.  You can imagine that allocation of water from smaller water bodies (e.g. river systems driven primarily by surface runoff) would be fairly sensitive to various elements of climatic change. A few dry years could lead to a big drop in available water, which could lead to effects such as increased conflict among users, lawsuits, and various other unpleasant things. Allocation of water from large subsurface aquifers would be less sensitive to changes. A few dry years have virtually no effect on the Oglala Aquifer, for example, making allocation less sensitive to intermittent drought. Of course, there could be indirect effects, such as increased overall demand. Imagine if people who’d been relying on water from more drought-affected sources all of a sudden want in on the more reliable water sources, substantially increasing long-term withdrawal. Clearly the allocation won’t keep up with demand, but not due to lack of long-term input. Here it is a human behavioral change in response to climate change that makes all the difference, not simply climate change drying up the system.

Finally, there’s the issue of adaptive capacity, or the ability of the assessment target to adapt to climatic changes or their effects. Here we get to one of our favorite examples of a system with high exposure, high sensitivity, and low adaptive capacity: the Colorado River Compact. When the Colorado River Compact was created, users were allocated a fixed volume of water from the River. While this wouldn’t be a problem if the Colorado River had the same volume of water every year, it becomes very problematic if, as has happened most years since the Compact was created, the volume of water available is less than the total volume of water allocated to users. Thus you could say that a fixed-volume water allocation system has low adaptive capacity relative to a system that allocates users a percent of total available water.

Stein's Sunburn Analogy for VAs: adaptive capacity = your ability to minimize harmful effects of exposure

For more examples of how to apply the climate vulnerability assessment concept to management measures or project design, check out Restoring the Great Lakes’ Coastal Future:Technical Guidance for the Design and Implementation of Climate-Smart Restoration Projects.  Although focused on restoration, the document goes through how both restoration targets and the project strategies.

Here’s another way to look at it that doesn’t get into any of the technical terms and definitions.  The sorts of climate change VAs you’re used to typically ask how climatic changes or their effects might affect the future persistence and function of the species, habitats, or ecosystems of interest.  But you could just as well ask how climatic changes or their effects might affect the future persistence and function the rules, regulations, or management measures of interest. The question is whether projected changes related to climate change pose a significant threat to our ability to successfully implement the policies or management measures we’re committed to or considering[i].

We hope all this has reduced rather than contributed to your confusion. If after reading this column and the materials we’ve suggested you’re still confused, let us know and we can try again! Our only indicator of whether we make any sense at all is feedback from people like you.

Conceptually yours,

The Mavens

[i] Paraphrased from the Puget Sound Nearshore Restoration Project’s Management Measures for Protecting and Restoring the Puget Sound Nearshore, Appendix B, Sea Level Rise Risk Assessment

Thanks to Bruce Stein of NWF for his most excellent sunburn analogy!