You say ‘HRV,’ I say ‘NRV’ …

Dave Skinner asked, “has anyone besides me noticed the change away from “historic range of variability” terminology to “NATURAL range of variability” in USFS planning processes?”

This terminology is pretty important, but I don’t think the Forest Service has handled it very well. The best source of the Forest Service perspective on this is in the EIS for the planning rule, Chapter 3, pp. 88-91. It recognizes that shortcomings of HRV as a management objective (including the role of climate change), and concludes that, “HRV provides an informative benchmark or reference for understanding landscape change.”

On the other hand, NRV (natural range of variation) is a requirement of the planning rule. A plan must include plan components that maintain ecological integrity (36 CFR 219.8, 219.9). Ecological integrity occurs when “dominant ecological characteristics (for example, composition, structure, function, connectivity, and species composition and diversity) occur within the natural range of variation and can withstand and recover from most perturbations imposed by natural environmental dynamics or human influence” (36 CFR 219.19).

The draft planning directives say that there is no difference between HRV and NRV: “’Natural range of variation’(NRV) is a term used synonymously with historic range of variation or range of natural variation. The NRV is a tool for assessing ecological integrity, and does not necessarily constitute a management target or desired condition” (1909.12 FSH Zero Code definitions).   However, if NRV=HRV and NRV is required, then there is a mathematical principle that says plans must plan for historic conditions.

The draft directives then try to create exceptions to the requirement in the regulations that conditions occur within NRV. I think it would be more defensible if the directives define NRV as conditions that would allow an ecosystem or species to “recover from most perturbations imposed by natural environmental dynamics or human influence,” and require an explanation of the rationale (based on best available science) when this is different from historic conditions, or when information about historic conditions is not available.

(Glad you asked?)

2 thoughts on “You say ‘HRV,’ I say ‘NRV’ …”

  1. This is what gives “scientists” and planners a bad name, and why federal land managers spend their time trying to figure out what it all means (rather than laying out cutting units or putting paint on “cut” trees)

  2. Wow, what a mass of gobblygook.
    Even if you have a forest outside any historic parameters, you could still be able to hide behind NRV if it eventually, even 500 years from now, becomes a forest again — burned or swatted.
    And I still think that natural undercuts historic. North America hasn’t been truly natural since the Indians showed up. Even the wildernesses left to nature were left that way because that was the most rational course of choice. By humans, with a history.
    Thanks for trying, Jon, but that kind of semantic gymnastics is no compensation for a good eye and a careful hand. How many little pine angles can dance on the head of a spiketop, basically.


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