Emily’s comment about barred owls reminded me of something I’ve been working on more broadly: when is it OK for humans to manipulate organisms, and when isn’t it, and who decides? It seems like it’s OK to kill one species to protect another species in the name of “retaining a species.” Perhaps it would matter (?) if the barred owl migration was “natural” or not.. but how would you tell, since colonization, climate change, introduced or not diseases, and a variety of other changes happen through time and are correlated. I don’t think we’ll ever tease the potential causes apart. And when each species declines, the ESA response seems to be to “protect more habitat”, which as we see, won’t always work.
So we’re trying to stop a possibly natural process (competition among species) in order to recreate past “naturalness”, or to keep going a maximum number of species, or because it’s the law of the land. This seems like something we’ll only be able to do in a limited number of cases. I wonder what principles will or should guide our choices? These are certainly not scientific questions, although the choices could be informed by science, including economics. It almost seems like the same action (say thinning trees) is considered to be “good” when its for restoration, but “bad” when it’s for protecting communities. Killing birds is “good” when it’s about protecting endangered species, and potentially “bad” when wind turbines do it. So if some purposes are better than others, then that’s not a science question at all. When does the end justify the means and perhaps more importantly, how does our system of governance deal with different points of view on the subject? Has their been a public comment period on the practice of killing barred owls?
Underpinning all this may be the idea of “keeping all the species where they used to be is necessary for ecosystem (integrity? health? function?).” But that’s not actually “natural” in any practical sense as Stephens, Millar and … (2009) say here.
Paleorecords in areas where abundant information exists can be used as a test of what has been sustained naturally overtime. When Quaternary vegetation records from the Sierra Nevada were assessed, Millar and Woolfenden (1999b) found that only a few conditions often associated with ecological sustainability concepts pertained. These included: (1) relative stability of the Sierra Nevada ecoregion, i.e., persistence of a distinct ecoregion over time, and, (2) persistence of overall species diversity at the scale of the entire Sierra Nevada ecoregion, with only one species, a spruce (Picea spp.), disappearing from the region about 500 000 years ago. Beyond these two features, however, other conditions commonly associated with ecological sustainability did not occur. At sub-regional scales within the Sierra Nevada, species diversity changed considerably at timescales of centuries to millennia. Movement of individual species meant that vegetation assemblages changed over time and/or shifted locations as species followed climate gradients individualistically (Woolfenden1996). Vegetation communities appeared sometimes to shift locations, when individual species tracked climate coincidentally, and in other cases, changed composition and dominance relations as species responded differently. Non-analog communities occurred transiently, such as the co-occurrence 20–30 thousand years ago in the southern Sierra Nevada of yucca (Yucca brevifolia) and Utah juniper (Juniperus osteosperma) with an understory of Artemesia tridentata, Purshia tridentata, and Atriplex concertifolia (Koehler andAnderson1995). Finally, historic fire regimes reconstructed from the Sierra Nevada have changed over time at multiple scales (Swetnam1993); however we recognize that the largest change in Sierra Nevada fire regimes occurred with the onset of fire suppression in the early 20th-century.These and similar records challenge interpretations of ecological sustainability that emphasize persistence of population sizes and species abundances, stability of native distribution ranges, and continuity of vegetation and wildlife community compositions. By contrast, we find that, of the diverse concepts commonly associated with ecological sustainability, only native species persistence within large ecoregional boundaries, such as the Sierra Nevada, pertains. Our goal here is not to imply that any combination of species would be acceptable in Sierra Nevada forests but that managers should not attempt to maintain all species at their present locations, as climate continue to change this will probably not be possible or desirable.
Of course, they’re not talking about a species being completely gone from everywhere. At some point, though, I think we may cross from seeking the “natural” to something sublimely unnatural.. the Disneyland equivalent of Nature.