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- James
Williams
- Department of
Biology and Interdisciplinary Studies in Aquatic
Resources
- St. Francis
Xavier University
- Antigonish,
Nova Scotia
Ecological Knowledge
Position Paper
A discussion of competing views of
ecological knowledge as it pertains to management of aquatic
resources is timely, given that many stakeholders in aquatic
resources have recently advocated incorporation of such
knowledge in future management schemes. What is interesting
is that although there is agreement that such knowledge is
important, there is considerable diversity among, and even
within stakeholder groups about what ecological knowledge
is. In fact, much of what is considered ecological knowledge
is merely biological information at a level that is quite
inappropriate for inclusion in management schemes (although
useful in its own right). If the eventual goal of these
exercises is to move towards some form of ecosystem-based
management, then it is important to identify the type of
information that has some potential to contribute to such
endeavours, and to identify where various levels of
information fit in the evolution of management
schemes.
There is a fundamental obstacle to
agreement among ecologists about ecological knowledge, and
this reflects two general approaches to the study of
ecology, one directed at the level of the organism, and one
directed towards the level of the ecosystem. As in most
fields of study, there is no clear demarkation between the
two approaches, and they represent the opposite ends of a
spectrum of research. Researchers who approach ecology from
the viewpoint of the individual investigate organisms and
their inter- and intra-specific interactions, as well as the
effects of the abiotic environment. These types of study
would include examinations of competition, predation,
community structure, population dynamics, and so on. At the
other extreme are those who study ecosystems, and the
processes that underly their function. Study at this level
ultimately involves the flow of energy through and the
recycling of nutrients within ecosystems, and may
concentrate on a particular trophic level, or on the
emergent behaviour of various ecosystem components, without
an understanding of the specific component processes. Both
of these approaches are valid and useful explorations of
natural systems, but both may not equally contribute
information that is useful from an ecosystem-based
management standpoint.
It could be argued that the
majority of ecological knowledge forthcoming from those who
make their living associated with aquatic resources is
directed at the level of the organism. Much of this
information will be about targetted, commercial species, and
include information such as gut contents, size and sex
distributions, and information on movement and distribution
(often expressed as catchability) related to a number of
physical parameters such as season, temperature, tide,
weather, and so on. Temporal changes and trends also figure
prominently in the recounting of ecological knowledge. This
type of information greatly adds to our understanding of the
basic biology of many commercial species, and it is
suprising how little is known about the basic biology of
many commercial fish and shellfish species, despite as much
as a century of publicly-funded research and management. For
example, until very recently, the only published
study that described the behavioural details of spawning
Atlantic cod (Gadus morhua) came out in the early
1960s (this lack of factual information did not, however,
preclude years of debate on the effects of trawling and
other fishing activity during spawning aggregations of cod).
Clearly, ecological knowledge has the potential to make a
valuable contribution in this regard. It also has the
potential to greatly aid the design and implementation of
sampling and data-collecting exercises. However, except for
some data which is useful in elucidating trophic
relationships, it is difficult to see how this type of
information could contribute significantly to
ecosystem-based management schemes.
To sustainably manage an ecosystem,
you must understand ecosystem-level processes, and the
limitations on these processes. Any aquatic ecosystem is
fundamentally limited by the amount of sunlight falling upon
it, which in concert with nutrient cycling determines the
base amount of primary productivity that drives the whole
ecosystem. A useful analogy is to consider earlier
pasture-based agricultural production. A given acerage of
pasture-land would support some finite number of beef
cattle, and this number was determined by the amount of
primary productivity, the grasses that the cattle consumed.
The pasture also supported a number of other organisms at
various trophic levels, such as bacteria, insects, reptiles
and amphibians, small mammals, and roving carnivores such as
hawks and foxes. If a farmer wished to increase the size of
the herd, it was necessary to clear additional pasture land.
Similarly, an aquatic ecosystem such as St. Georges Bay is
limited by the finite amount of primary productivity that
occurs there. Regardless of whether this primary
productivity comes from phytoplankton, or marsh grass, or
seaweed, or benthic diatoms, there is a finite amount
available which must support all other organisms in the bay.
The energy and nutrients associated with this plant material
is then transferred up through the various trophic levels,
with substantial losses during each transfer. And, as in the
case of the pasture, the primary productivity supports a
certain amount of some target species, such as white hake or
cod, as well as non-target species such as tunicates,
sculpins, skates and so on. Clearly, effective sustainable
management of the St. Georges Bay ecosystem would require
information about ecosystem-level processes, such as average
annual levels of primary productivity, approximate biomass
of organisms that constitute the different trophic levels,
fluxes of organic and inorganic matter into and out of St.
Georges Bay, and so on. Ecological knowledge from aquatic
resource users does not, for the most part, encompass these
issues, as it is usually directed at the level of the
individual species.
Past management of aquatic
resources has been at the level of the individual species.
It is partly the global failure of such approaches to
sustainably manage aquatic resources that has resulted in
many diverse groups calling for an ecosystem approach.
Curiously, although these groups pay significant lip service
to the concept, they show little evidence of seriously
trying to gather information about ecosystem processes. The
Department of Fisheries and Oceans (DFO) has, at various
times, both internally and publicly stated the need to
incorporate ecosystem-based management principles. Despite
this intention, management is still structured around
individual species. Herring biologists study herring, cod
biologists study cod, and lobster biologists study lobster.
The fact that all three may co-exist in the same ecosystem,
and depend ultimately upon the amount of phytoplankton
produced in the water, is not sufficient, as yet, to break
down existing organizational barriers, or have management
make a serious fiscal commitment to understanding marine
ecosystems. Similarly, community-based management of aquatic
resources often claim ecosystem-based management as a
guiding principle. Despite this declaration, it is unlikely
that we will see CBM committees expending money on
flourometers and plankton nets in the near
future.
Part of the resistance to a real
ecosystem-based management approach is the difficulty in
applying it to individual species. When one is trying to
understand fluctuations in abundance and biomass of a
particular trophic level, the inter- and intraspecific
interactions are often too complex to model or predict. So,
one may determine that a particular area will support a
certain biomass of groundfish, but perhaps not how much of
that tonnage is haddock, and how much is sculpin.
Mass-balance ecosystem-type models with the ability to
predict effects of management decisions on individual
species are being developed, but it remains to be seen
whether or not they will be more effective than the
population dynamics models of the past. Another difficulty
with an ecosystem-based approach is that the majority of
existing information, especially information that represents
a significant time series, is directed at the species level.
A compromise position that is being tried in some areas is
the use of hybrid multi-species models, which use the
single-species population dynamics models, but attempt to
include species interactions in their design. At the same
time, if we are to truly understand the functioning of
marine ecosystems at a level where we can assess the impact
of harvesting practices, and also assess the effects of
large scale changes such as global warming, we must
intensify efforts to collect basic information about
ecosystem structure and function.
In summary, the ecological
knowledge that can be provided by aquatic resource users
will be very useful in expanding our knowledge base
concerning many commercially harvested species. With respect
to a real understanding of marine ecosystems, with the
eventual goal of sustainable management of these ecosystems,
this information will have limited value.
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