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| from: http://www.fao.org/zhc/detail-events/en/c/233765/ |
The ocean is
beneficial for societal wealth and human development. The oceans
offer access to food, materials, energy, and recreational
opportunities. Many states take (and took) initiatives to master
their access to marine resources; now often under a “blue”
catch-word [a]: “The
'Blue Economy' concept has attracted much interest in international
fora and become a key to development strategies of international
organizations. This cross-cutting initiative aims to provide global,
regional and national impact to increase food security, improve
nutrition, reduce poverty of coastal and riparian communities and
support sustainable management of aquatic resources.”
It is likely that
seas and oceans, even more than today, will be a theatre of competing
economic interests. Already today, the convenient availability of
ocean resources has put high pressures on the health of the ocean,
e.g.: overfishing shifts balances of ecosystems, pollution trough
extraction industries threats regional seas, marine litter spoils
recreation, plastic threatens marine life along the entire food
chain, or alterations of coastal zones destroy unique habitats. The
risk is high that these pressures increase when more “blue economy
strategies” get implemented. In that context, an index to describe
the overall ‘health of the ocean’ in a standardized manner would
be much needed and could be a very useful management tool.
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| from: http://www.oceanhealthindex.org/ News/Top_10_Clean_Water_Countries |
Drawing on
experiences in coastal zone management, comprehensive assessments are
emerging, which consider a composite of oceanic features that
influence societal wealth and human development. The
wealth of marine information that is available nowadays through a
multitude of studies may be incomplete, but a tentative assessment of
global ocean-health issues is possible. Against
this backdrop, proposing comprehensive ocean-health index [1] and
making it available [b] was a very important step forward towards a
sustainable human use of the ocean; although some may consider this
step as “bold” or even “too bold”.
Ten amalgamated assets
The ocean-health
index amalgamates ten societal assets [c] undertaking one composite
assessment of reference values, current status and future status. The
ten assets were selected to cover a wide range of ecological, social,
and economic benefits for a wide range of “use cases”. The score
of the ocean-health index, a single number, shall describe the state
of the human-ocean system as a composite-asset. The main assumption,
implicit to the index, is that a combination of the ten assets should
be preserved for any healthy human-ocean system, although the
combination may vary regionally and in time.
The ocean-health
index is presented annually at country/regional level and at global
level. For 2012 and 2013, the score of the ocean-health index was
estimated to be a modest 65 of 100 when averaged at the global level.
The score of individuate countries varies between 41 and 94; and
countries of very different natural and economic setting have the
same score like Norway and Netherlands (74) compared to Iceland that
scores 58.
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| from: http://medsea-project.eu/ |
The score for the
ocean-health index is calculated as the weighted arithmetical average
of the scores for the ten assets on which the index is built.
Selecting these assets, identifying indicators describing them,
gathering data measuring the indicators is a tedious and complex
undertaking, which in itself gives ample space for biases, nuanced
choices or simple errors. Improving the ocean-health index is subject
of research and study that, by no means, renders the index
meaningless, because it provides a means for global benchmarking and
comparison that otherwise would be missing.
Compared to
addressing possible defects “of substance” of the ocean-health
index, it seems ‘picky’ to question the use of a “weighted
arithmetical average” to calculate the score of the ocean-health
index. Nevertheless that was done recently [2], for very good
reasons, and with lessons that may serve as examples also for other
index that calculate a score for a set of assets.
An innocent average ?
The mathematics
of a “weighted arithmetical average” that is used to calculate
the ocean-health index looks innocent and non-problematic.
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| from: http://www.cdc.gov/nchs/tutorials/nhanes/ NHANESAnalyses/DescriptiveStatistics/Info3.htm |
An “arithmetical
average” of single marks gives each mark the same impact on the
composite mark. That makes good sense if a feature is marked several
times, a set of measurements, a sample, is obtained, and thus the
elements in the sample are belonging to the same kind but vary
randomly. Using weights is a simple and transparent approach to set
preferences between marks for features of similar kind, i.e. to
account for some non-random variation within a sample of “features
of about the same kind”.
Thus, in
face of the intrinsic complexity to assess in a composite context the
different assets that are underpinning the ocean-health index, taking
an approach of “one asset one vote”, i.e. arithmetical average,
looks like a fair, “democratic” first choice. Furthermore, giving
different assets different weights looks like a fair option to
reflect social or political choices without excluding a “minority
asset”. Nevertheless, just these simple first-hand choices are not
innocent but set a rather radical “normative frame” [2] for
managing a set of “assets” by means of a index, which may limit
the usefulness of the index.
Using an
“arithmetical average” to obtain a score for a set of assets
implies a paramount assumption, namely that “unlimited substitution
possibilities” exist among these assets to obtain the same score.
In that context, “substitution” means that under-performance for
one asset can be balanced by better-performance for another asset;
“unlimited” means that under-performance for one asset is not
limited by a lower boundary; and “possibility” means that
better-performance for any asset may balance under-performance of any
asset. These assumptions are quite radical, indeed.
Using a “weighted
arithmetical average” does not alter the assumption, although it
modifies the “cost” of the substitution; i.e. performance for an
asset with low weight has to improve much to balance a minor drop of
performance of an asset with a high weight.
A radical “normative frame” ?
To perceive how
radical is the assumption of “unlimited substitution possibilities
among various assets”, one may assume: (1) a shopping list of ten
items for the dinner table, (2) getting these items in different
quality or quantity, but so that (3) the average quality of the
dinner is the same. Evidently, a good starter may make good for a bad
desert, or a good wine (or beer) compensates for…; but “unlimited
substitution possibilities among the various parts of the dinner”?
Common sense tells that this may work, indeed, but at best for a
“below-standard dinner”.
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| from: MARUM - Center for Marine Environmental Sciences (distributed via imaggeo.egu.eu) |
Evidently,
“unlimited substitution possibilities among various assets” is a
framework for “a manager’s dream”. Such a framework maximises
the number of operational alternatives to amalgamate assets although
respecting social choices of different assets through their
weighting.
However,
“unlimited substitution possibilities among various assets” is an
exceptional case. It is ”the real-world’s manager’s headache”
that amalgamating assets is limited by the substitution potential
among them. The substitution potential may be limited for ecological,
technical or social preferences. Considering the ten single assets
that are amalgamated into the ocean-health index, it seems possible
that they substitute each other to some degree, but it is very
problematic management guidance to assume that they substitute each
other fully.
Strong or weak sustainability ?
Extremes in
degree of substitution possibilities between assets is summarized in
two alternative concepts, of either “strong
sustainability”
or “weak
sustainability”.
The former requires keeping all assets above critical levels, thus
avoiding any substitution between them. Under the concept of “weak
sustainability” substitution
between assets is unconstrained and can be done without any limits.
That latter
concept of “unconstrained substitution” is applied for the
ocean-health index by the choice of the mathematical formulation how
the average score of the ocean-health index is calculated [2]; namely
using a weighted arithmetic mean.
The assumption,
which is implicit to the mathematics, namely “unconstrained or
unlimited substitution”, is unrealistic and may misled. However,
it goes without saying that experienced managers of marine resources
would be aware of limitations to substitution of assets, although
implementing that awareness for a set of assets in a competitive
environment is not only an intellectual challenge.
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| Border between open sea water and a plum from the Mzymta river (Sochi, Russia) from: Alexander Polukhin (distributed via imaggeo.egu.eu) |
Obviously,
intermediate levels of substitution may be achieved for many
real-world situations and their description by means of an index. And
evidently, for many real-world situations it will be difficult to
determine “what are boundaries to substitution?” Manifestly, any
intermediate level of substitution for assets underpinning the
ocean-health index will depend on the specific ecological-human
intersections of the respective human-ocean system. Whatever is
obvious, evident or manifest, it will be hard and tedious work to
narrow the range of substitution possibilities, and in some
circumstances “strong
sustainability”
should be applied to guide management choices, simply.
The mathematics
to describe “intermediate levels of substitution” are available.
Likewise the tools are available to study implications of having
chosen a specific mathematical method to describe “intermediate
levels of substitution”. They are used, for example, in social
choice theory [d]. Aggregation of individual asset with constraint or
limited substitution into a composite scores can be described using
‘generalized
averages’ [e];
with arithmetic, geometric or harmonic average as special cases of
the ‘generalized
averages’.
Composite averaging procedures and intermediate level of substitution
Choices of
limited substitution possibilities for the various assets of the
ocean-health index can be made [2] applying state of the art
knowledge on natural resources and ecosystem assessment, which are
reflecting the state of the human-ocean system, and using appropriate
mathematics, i.e. specific functional forms (“functions of
functions”) [f].
The mathematics
for calculating the index can get increasingly composite by working
in a nested manner, using generalized means, applying variable
setting of substitution with constraints on the overall score for the
less-performing assets, and fixing “hard” lower boundaries.
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| from: http://ecolutionist.com/the-new-ocean-health-index -measures-human-impacts-on-our-oceans/ |
Evidently, such
kind of “composite averaging procedure” lacks the simplicity of
the arithmetical average. The “composite averaging procedure” is
more like an elaborated model of the substitution possibilities,
which has to be analysed with care; not only for his non-linear
behaviour.
Notwithstanding
the complexity, such a model could capture our best understanding of
the functioning of the ocean-human intersections though appropriate
mathematics. As such it may be a very useful research tool.
However, the
complexity of the model may be considered as much too high to abandon
the “weighted arithmetical average” because of its relative
transparency for many users. Thus for management environments the
“weighted arithmetical average” may be preferred.
Ocean-health index with intermediate level of substitution
Recalculating the
ocean-heath index with a modified methodology to calculate the
average score [2], showed a considerable dependence of the
ocean-health index on the choices for the substitution possibilities
including substantial swings of countries between camps of
“well-performing countries” and “under-performing countries”.
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| The English Channel in Cap Blanc-Nez; above the two ships a brown pollution layer; probably containing NO2 and aerosols. from: Alexis Merlaud (distributed via imaggeo.egu.eu) |
The bulk result
of the study [2] is that the global ocean-health index decreases by
20%; namely from a score of 65 of 100 to the score of 52 of 100 if
the “weighted arithmetical average” is replaced by a revised
methodology limiting substitution among assets. The revised index
reduces less-realistic possibilities for offsetting poorer
performances in certain assets by better performances in other
assets. The drop of the global ocean-health index is important, and
possibly many decision makers, who would find a score of 65 of 100
“still tolerable” -
two good for one bad -, would
modify that view for a score of 52 of 100.
Even more
striking is the finding [2]:“...when
we turn to the assessment of individual countries. Countries with an
unbalanced performance across the assets significantly deteriorate in
the ranking compared to countries with a balanced performance. For
example, Russia and Greenland fall in the ranking for 2013 by about
107 and 118 places (out of 220) respectively, while Indonesia and
Peru improve by about 78 and 88 places respectively.”
Similar striking changes are observed regarding the assessment of
change over time, for one out of four countries the direction of
change is inverted.
What is the lesson to draw?
Th ocean-health
index is useful because of the limitations of choices that were made
when designing it. The challenge to describe a set of assets through
a single index drives insights into the human-ecological
intersections of the human-ocean system, including the issue of
appropriate mathematical description.
A first insight to keep:
Setting up an
ocean-health index [1] was a very relevant endeavour, and is a
lasting contribution to the management of the human-ocean system. An
ocean-health index could be a tool for comparison of national and
regional policies, benchmarking, and qualification of development
options, which is much needed to manage global commons like the
ocean. Implications of the (simple) mathematics to calculate the
ocean-health index have been analysed [2].
 |
| from: http://serc.carleton.edu/NAGTWorkshops/ health/case_studies/plastics.html |
The result of the
study indicates that the mathematical method chosen for calculating
the average is causing bias of the index. The method to calculate the
score of the index by “weighted arithmetical average”, makes the
index insensitivity to less-appropriate choices to substitute assets
for which performance is low by better-performing assets. This
feature of the index limits the use of index. The possibility of
unconstrained mutual substitution between assets within the composite
score requires adjustment. Without such adjustment [2]: “policy
assessment and advice based on an index with unlimited substitution
possibilities could result in (a) certifying a healthy human-ocean
system for countries that in reality neglect important aspects of
ocean-health and (b) identifying development trajectories as
sustainable although this is actually not the case.”
A second insight to keep:
The assessment of
the various oceanic features relevant for societal wealth and human
development is improved, if substitution possibilities among
different assets are constrained. Evidently, the substitution of
different assets is a societal endeavour. It requires knowledge,
social choices and norms and particular the latter may evolve and
vary among societies.
Nevertheless, any
substitution possibility should be limited and confined by boundaries
of the elasticity of the ocean system, if we know the ‘elasticity’
otherwise the “strong sustainability concept” or the
“precautionary principle” should be applied. For being practical,
the retained substitution possibilities should provide for some
elasticity to have a margin for management decisions -
not everything goes, not all is forbidden – to
render the ocean-health index a tool with operational value.
A third insight to keep:
Furthering the
analysis of suitable substitution of assets and how to describe the
substitution process in mathematical terms is needed to properly
evaluate benefits, risks and development options of the ocean-human
system.
 |
| from: http://ocean.si.edu/blog/ penguin-health-equals-ocean-health |
For the best or
the worth, a common and robust ocean-health index is a much welcomed
management tool, and possibly the ocean-health index will be part of
any mature ‘blue economy strategy’. Thus, it is important to
design the index in a manner that is sound and practical. The
alternative would be to manage all assets one-by-one using the
“strong sustainability concept”, what possibly would end in a
political process to retain on a case-by-case only those assets that
are considered most relevant. In that situation any comparison of
national and regional policies, benchmarking, and qualification of
development options would be far more difficult.
Thus, one
composite index has a strong appeal. However, attention should be
given to the complexity of the averaging procedure, which if too
complex or perceived as too complex would hamper application of the
index. To recall, the attractiveness of calculating the ocean-health
index by a weighted arithmetical average is the simplicity of the
procedure that is understandable for many.
Possibly a two
tiers approach may provide a useful compromise. Tentatively, such a
compromise could be: (i) apply the “strong sustainability concept”
to identify assets that either match this concept or fail, (ii)
calculate the score of the ocean-health index for both subsets, (iii)
calculate the arithmetical average of both sub-scores (weighted by
the number of assets in each set) to get the score of the
ocean-health index, and (iv) present this score with the scores for
the sub-indexes as lower and upper bound.
Post Scriptum:
How to generalize
this experience? What has been discussed above for the ocean-health
index applies "mutatis mutandis" to any index that gives an average
composite score of several assets that can substitute each other only
partially.
Ukko El'Hob
[c] The single
assets of the ocean-health index are: (1) Artisanal Fishing
Opportunities, (2) Biodiversity i.e. species and habitats, (3)
Coastal Protection, (4) Carbon Storage, (5) Clean Waters, (6) Food
Provision i.e. fisheries and aquaculture, (7) Coastal Livelihoods &
Coastal Economics, (8) Natural Products, (9) Sense of Place i.e.
iconic species’ and special places, and (10) Tourism &
Recreation [x].
[1]
An index to assess the health and benefits of the global ocean
(2012). Benjamin
S. Halpern, Catherine
Longo, Darren
Hardy, Karen
L. McLeod, Jameal
F. Samhouri, Steven
K. Katona, Kristin
Kleisner, Sarah
E. Lester, Jennifer
O’Leary, Marla
Ranelletti, Andrew
A. Rosenberg, Courtney
Scarborough, Elizabeth
R. Selig, Benjamin
D. Best, Daniel
R. Brumbaugh, F.
Stuart Chapin, Larry
B. Crowder, Kendra
L. Daly, Scott
C. Doney, Cristiane
Elfes, Michael
J. Fogarty, Steven
D. Gaines, Kelsey
I. Jacobsen, Leah
Bunce Karrer, Heather
M. Leslie et
al.,
Nature 488. doi:10.1038/nature11397
[2]
How healthy is the human-ocean system? (2014). Wilfried Rickels,
Martin F Quaas and Martin Visbeck. Environmental
Research Letters Vol. 9(4).
doi:10.1088/1748-9326/9/4/044013
