Pressure classification methodology?
buddrw at kgs.ku.edu
Wed Mar 5 11:43:07 EST 2003
Nick Polunin has pointed out that there are good ways to get indicators or
proxies for single variables or clusters of closely related effects. The
issue is very different once you try to do some sort of multi-variate but
quantitative assessment. My opinion is that the Reefs at Risk approach is
about as detailed, as well tested and justified, and as useful as one can
hope for, and although it could be 'tuned' for specific locales or concerns,
it's a wheel that not only doesn't need reinventing, but also one that
probably can't realistically be improved on a whole lot (see below).
There are whole schools of analysis devoted to this sort of thing -- Kerry
Turner and his colleagues like the PSIR (Pressure-State-Impact-Response)
conceptual model; you can find out more about that by going to :
http://www.nioz.nl/loicz/firstpages/products/fp-products.htm, and under the
Reports and Studies category go to R&S #11 (downloadable pdf file).
Personally, I do not find this approach terribly useful for serious
quantitative analysis, but it does raise some very important conceptual
points -- specifically, by separating pressure from impact and including the
state of the system. The same amount of nutrient dumped on a well-flushed
fore-reef and in a relatively stagnant lagoon will have very different
impacts -- and hence, operationally, be functionally different pressures.
Similarly, response to coral mortality will depend on the reproductive
strategies and potentials of the survivors and on connectivity to other
sources of propagules.
I would suggest that a lot of work has been done on classifying reef
vulnerability by looking outward toward the stresses; I don't think the
level of systematic classification of the relation of reef community
characteristics (areal size, diversity, cover/population, regional and local
environmental settings, recent history of stress or damage, etc.) to
vulnerability has kept up with that, and at local-to-regional scales that is
a key component.
I am a little confused by your request -- you say "I am not really
interested in quantifying the impact intensity, just classifying reefs based
on the presence of each pressure." but you continue to say "Justification
would be based on impact magnitude in terms of frequency/ damage potential."
If you are looking at impacts you are going to need to deal with
nonlinearities, thresholds, and synergies -- reducing salinity from 34 to 28
psu might not have too much effect; reducing it from 28 to 22 would likely
be catastrophic. And the outcome of the catastrophe would depend on how
much sediment and nutrient loading came with the fresh water [ Suggestion --
test whatever classification system you come up with against the
well-documented history of Kaneohe Bay]. This raises a number of other
issues -- we tend to think of anthropogenic impacts in terms of how much
foreign stuff people dump in the water or how many organisms they kill, but
the second-order pressures resulting from land and water use can have major
effects that aren't fully considered (floods, for example, may be either
controlled or exacerbated by human activity).
And a final point -- in an era of disease, bleaching, and climate change,
it may be pretty short-sighted to do pressure assessments only on the basis
of local anthropogenic factors, and essentially impossible to interpret or
understand reef 'responses' only in those terms.
sarah hamylton wrote:
> Hello everyone,
> I was wondering if someone could advise me on some work I am doing for my
> dissertation. I am seeking a classification scheme for categorising reefs
> on the basis of the pressure they are under. Thus far, I have only been
> able to find a report that uses distance from the nearest populated area-
> this is included in my data set but doesn't give any indication of the
> type of pressure. I am not really interested in quantifying the impact
> intensity, just classifying reefs based on the presence of each pressure.
> The data set I have is similar to a Reefcheck one- it assesses a number of
> pressures on a semi-quantitative scale- rating presence from none to
> heavy. Im tempted to make up my own classification scheme, assigning
> weights to the different influences and then attempting to justify the
> weightings I have used. Justification would be based on impact magnitude
> in terms of frequency/ damage potential. Maybe also incorporating papers
> written on influences that are known to be particularly problematic in the
> study area. I cant help thinking that this will become a little
> subjective though, I am tempted to weight the presence of sewage pollution
> heavier than tourist diving as the latter is present at all my study sites
> whereas the former only has a presence at three out of twenty two study
> sites. Does anyone know of any set methodologies for categorising
> individual reefs on the basis anthropogenic pressures present?
> Any help would be much appreciated.
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