Habitat management: see Swengels' papers

John Shuey jshuey at TNC.ORG
Thu Jan 24 09:20:29 EST 2002

> With all the recent discussions of habitat and management recently, I
> suggest that people might like to read a series of papers by Ann and Scott
> Swengel who have studied the impact of different habitat management
> strategies (none, haying, burning, grazing) on butterfly populations in
> prairie and oak barrens in Wisconsin and other mid-western states. Their
> work illustrates the complexity of the problem. This paper
> published in the
> journal Biodiversity and Conservation (10:1757-1785) in 2001, notes that
> most ecologists assume that the prairies have been maintained by
> fire which
> has inhibited succession and that most prairie specialists are therefore
> fire-adapted.  Based on multiple regression analyses of over 120,000
> butterly records in 125 barrens and 106 prairie sites, they found that
> burning generally favored higher numbers (my interpretation) than "idling"
> in  barrens but NOT in  prairies.  They also found many other
> inconsistencies indicating that there is no single practice that is
> uniformly better than any other practice in all habitats or even in all
> prairie habitats. They caution that managers should “avoid overreliance on
> one management type over others".
> Mike Gochfeld

I suggest that you look at "real" conservation biology literature before you
hype the Swengel's work too much.  The research in question suffers from
many problems - like

1), ignoring the bottle neck effect of fire suppression of habitat size
(they use today's remnant size and ignore the fact that most of their study
sites went through major reductions in size (usually 75% reductions in
available habitat due to woody encroachment) - so a 200 acre reserve today
may have had about 50 acres of prairie habitat before the site was managed
(fire and chainsaws usually - this was a major criticism of the attack on
Iowa prairies in NABA recently):

2), ignoring all concepts of island biogeography and species equilibrium

3) equating large populations with the concept of increased viability (most
conservation biologists are more concerned with minimum dynamic areas needed
to support populations and ecological redundancy at landscape scales

and most grievously 4) the focus on management of a single taxonomic group.
The "hay prairies" touted as the perfect answer to butterfly management are
extremely well known for the screwed up nature of the botanical community (a
recent review of federally endangered Mead's milkweed indicates that these
populations haven't set seed for a couple of decades in Missouri Hay

 The Swengles and other "anti-burning" butterfly types are roundly ignored
by the conservation community for several reasons:

1: there is a vast literature on the role of fire in these ecosystems and
the role it plays in maintain dynamic and species rich communities - look at
your own Pine Barrens and the role that fire suppression has played in the
loss of legumes and other forbs from the herbaceous community (the result of
nitrogen enrichment due to lack of fires).  At the Lep Soc Meeting a few
years back I heard - and I quote" There is no science behind the ecology of
fire".  Wow, as long as you ignore fifty or so botanical journals - you
could be right.

2: no-one in the conservation community believes that fire should be used
with abandon.  Long before the Swengels, you had Ron Panzer pointing this
out for invertebrates, grassland bird folks pointing out the problems with
habitat structure, and herp folks talking about high mortality rates.  The
presentation of their arguments as "them versus the pyro-botanists" has only
created the a lack of good will between land managers responsible for ALL
biodiversity on a site and the Swengels who obviously don't give a royal
damn about anything but butterflies and birds.  The Swengles and their
groupies have literally created and maintained a false dichotomy between the
two camps - and anyone who has every seen Ann scorned in public understands
why the typical busy person doesn't want to deal with them. (a better
characterization of the two groups is that one camp views fire as an
essential tool that has to be used with caution  while the other camp is
vehemently anti fire - most conservation biologists don't see room for
compromise - myself included)

3: No-one is interested in prescriptive single taxa management
recommendations in the conservation community at this point in time - its
that simple.  With the vast literature available on ecosystem dynamics,
minimum dynamic area concepts, ecotonal flux and succession, the Swengles
are pushing a "static management regime" to maintain a single target group.
Life and ecosystems are too complex to even try and digest the flat earth
approach to conservation biology.

I have to admit that I have my own personal reasons for ignoring this work.
I reviewed several of these manuscripts in earlier forms for various
journals.  I always sign my reviews and these manuscripts were all rejected.
Now I see these same papers kicking about (with problems glossed over - like
the fact that pollard transects for S. idalia were used in Wisconsin and
counts from the hood of the car using binoculars were used in Missouri - and
then the data statistically compared) and I AM LISTED IN THE ACKNOWLEDGMENTS
of my comments were addressed.  This is clearly a breach of ethical
behavior - implying that I endorse the paper that I in fact trashed.

And I think that this sort-of encapsulates the entire attitude of the
Swengles - fast, loose, and oblivious.

(Look for a real paper on this issue in the next issue of cons biol - w/
real experimental design, controls etc - novel but kinda like science as it
is practiced in the rest of the world).

John A. Shuey
Director of Conservation Science
Indiana Office of The Nature Conservancy
1505 N Delaware Street, Indianapolis, IN 46202



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