standardization of environmental data and information - International ...

differential response of the community at the impact site may be due to
natural cycles that vary spatially 3 . That is, any differences between the impact
site before as compared to after the anthropogenic activities could not be
interpreted as a consequence of these activities.
Bernstein and Zalinski 4 and Stewart-Oaten et al. 5 suggested an
improved sampling design referred to as BACI (Before-After-Control-Impact).
They argued that replicate samples should be taken several times before the
onset of anthropogenic activities and several times after, at both the impact
and control sites. This would provide temporal replication and reduce the
likelihood that any observed interaction was due to chance environmental
variation. However, this does not deal with the main problem – that the two
sites can have different temporal patterns of variation that have nothing to do
with anthropogenic activities.
In a series of papers, Underwood 6 described sampling and analytical
solutions to these design flaws in environmental impact studies. First, one
should use multiple control sites. It is often impossible or impractical to have
multiple impact sites, but there is no reason not to replicate control sites. The
multiple control sites will provide insight into natural patterns of spatial and
temporal variation in the target communities. The basic idea is that an impact
would cause a change in the response variable (e.g. population size) before
compared to after the onset of anthropogenic activities that exceeded the
average change in the controls over the same period. Second, each station
should be sampled several times before the potential impact and several times
after, providing temporal replication. Finally, an impact can be identified from
a comparison of various interaction terms in an Asymmetrical ANOVA 7 .
Basically, the interaction in time between the impacted and control sites
should be different from the naturally occurring interactions in time among the
control sites.
3. Proposed Sampling Design
Based on these studies, I describe a sampling programme with an
appropriate design for statistically detecting an impact from polymetallic
nodule mining operations in the deep sea. The design I propose represents a
bare minimum sampling programme. Appropriate levels of replication will
need to be determined from a power analysis 8 once the response variables
have been chosen, levels of acceptable change are determined and some
estimate of the natural variability has been made.
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