[Summary]: Systems for comparing the value of natural areas

Kate McCombs kate at capella.inmap.co.nz
Mon Apr 29 02:41:41 EST 1996

Earlier this month I posted the following message.  I have received
a number of replies which are summarised below.  My thanks to those
who replied	

> I'm looking at ways of comparing the values of natural areas.  Any pointers
> to publications or web resources dealing with ways of assigning numerical
> values to attributes such as rarity, bio-diversity, unusualness, size etc.
> I'm particularly interested in methods that have been used to 'average' scores
> to allow an overall ranking of different sites.  Simply taking the arithemetic
> average of the scores of each attribute has the undesirable result of assigning
> a low score where a site has outstanding value of one attribute, but low scores
> for all the others.  Are there any methods of score aggregation that avoid
> this type of problem that have been used?
> The other issue I'm interested in is methods for comparing dissimilar sites,
> e.g.a wetland and a forest? 

From: "MaryAlice Snetsinger" <maryalice_snetsinger at pch.gc.ca>

     In Ontario, a wetland evaluation system has been developed that
     compares wetlands (including different types).  There are some
     shortcomings to the system, but it is not bad.  It attempts to
     compensate for the problem of one outstanding attribute but a low
     score by breaking the assessment into 4 areas (biological,
     hydrological, social and special features components).  The final
     "significance" of the wetland is then based on so many points OR on so
     many of the components having more than a set value.

From: Ralf Bischoff <bisch at zfn.uni-bremen.de>

I´m sorry Kate but I guess there´s no way of quantifying the diversity 
of life. Comparing different natural ares will always be made by your 
own point of view. Maybe you´d like some simple values just
useful for some basic guesses of how the area is like: you may find some 
in any basic ecology-books (e.g. that from Begon, Harper & Townshend).

A little more sophisticated approach to valuing areas is from Ellenberg. But 
there you will only estimate the areas in terms of wet to dry, or from cold 
to hot for example. You also may use any kind of statistical approach, but 
with this you always have to ask yourself:"What the hell am I gonna say with 
this?". So to my opiion, don´t try to evaluate, better try to describe and 
make your own appreciations.

If your in need of any of the mentioned references feel free to write me, I´ll 
get them to you.

From: Fbcatchpol at aol.com

Try Floyd Swink & Gerould Wilhelm.  Plants of the Chicago Region. 1994. They
have a nice system for rating natural areas.  Their system rates sites by the
number of habitat restricted (or remnant dependant) species each site has,
and incorporates overall richness as well.  This is different from the more
common rarity indices.  It has the added advantage of allowing comparisons of
the quality of different ecosystems, and valuing high quality sites of more
common ecosystems, as well as high quality sites of rare ecosystems.

Floyd Catchpole      Kansas State University, Biology Dep't., Ackert Hall,
Manhattan, KS 66506  USA     phone (913) 587-4630 e-mail: FBCatchpol at aol.com

"About 90% of our native flora is restricted to the stable habitats provided
by our original plant communities, so an understanding and stewardship of
such areas is critical if we are to carry forward into the future a
possibility of association with living things other than ourselves, a few
weeds, and cultivars." - Floyd Swink & Gerould Wilhelm.  Plants of the
Chicago Region pp 42.

From: Gary L. Wade, Ecologist, gwade at moose.uvm.edu, USDA Forest Service 

A tremendous problem with "scores" and indices is the loss of information
that comes with their use.  What you describe is common, and one of my pet
irritants about the ways of many of my fellow ecologists.   Data on
diversity, biodiversity, what-ever, should not be condensed any more than is
necessary to evaluate it.  The different dimensions of biodiversity should
be evaluated on their own merits: species richness, number & identity of
rare, threatened or endangered species, flux of populations, uniqueness of
the habitat or community, the role of the area in question in the larger
landscape now and its expected role in the future.  I could go on and on.
If you condense all of this into one or a few numbers, who will understand
you besides another ecologist?  Keep it meaningful.  Most people are capable
of handling more than one concept at a time.

>The other issue I'm interested in is methods for comparing dissimilar sites,
>a wetland and a forest?

How unique or representative is each in the larger landscape?
What are their relationships to the larger landscape?
What are their functions in the larger landscape, region, or biome?
  Are they waypoints or stepping stones in short or long migration routes?
  Do widely dispersed species require them for reproduction--especially
Do they have species in common--are they providing different needs to
species of interest?
What is their relative diversity compared to regional standards?
Who are the stakeholders in each?  What stakes do they have in each?  How
will these change with time?

Please don't consider my reply as a flame, just questions, and my opinion.


You asked for "ways of comparing the values of natural areas" and "methods
for comparing dissimilar sites, e.g. a wetland and a forest?"

One measure for comparison of biodiversity is "relative richness,"  the
ratio of found species richness to the expected species richness of an area
of the same size in that biogeographical region.  I doubt your library has
"Transactions of the Kentucky Academy of Science" in which Ralph Thompson
and I published on this method.  Send me your postal address and I'll put a
reprint in the mail.

However, relative richness should not be the only measure considered!

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