Geoscience Reference
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high value planning units further downstream).
Similarly, when considering smaller, first- to
third-order planning units, we sought where
possible to identify high value sites containing sets
of adjacent small catchments to facilitate more
efficient management through the creation of
reasonably sized management units. This identified
an initial set of 94 high value sites.
The national gap-analysis rankings were then
examined, focusing on those non-protected
planning units with the most potential to
complement already protected planning units.
These were used to identify a further 33 high value
sites, many of them having direct connectivity
with protected planning units. Finally, to ensure a
degree of coverage across all biogeographic units, a
further 41 high value sites were added from the top
5% of planning units from the regional rankings,
mostly in biogeographic units having few or no
planning units with high rankings in either of the
two national analyses.
condition; note the geographic clustering of
priorities given to interconnected planning units
within large catchments in Plate 19a.
A subtly different set of priorities is indicated
from the second set of national rankings in which
planning units having 80% or more of their
extent already protected were retained until all
non-protected planning units had been removed
(Plate 19b). Here, rankings shown in green
indicate the relative priority of sites within the
21.1% of planning units already having substantial
protection. By contrast, rankings shown in shades
of blue indicate priorities for the remaining
non-protected sites, based on their ability to
complement the biodiversity values of those sites
already protected.
Results from the regional rankings are broadly
similar to those from the initial national analysis,
with high priority generally given to inter-
connected sets of good condition planning units
(Plate 19c). However, there are sometimes marked
differences between the national and regional
analyses that reflect the more restricted geographic
contexts of the latter. For example, biogeographic
units that have been extensively modified by
human activity will always have 10% of their
sites ranked highly, even though they may have
few if any sites that are highly ranked nationally.
However, sites may also be ranked highly in
regional analyses because the environments that
they contain, even though widespread nationally,
are rare regionally.
Results
Ranking analyses
Rankings from the Zonation analysis of the
combined national set of spatial data (Plate
19a) indicate the order in which planning units
should be protected to maximize the protection
of a full range of river environment types,
subject to some target level of overall geographic
protection. For example, protection of the highest
priority sites (dark blue in Plate 19a) would
protect 10% of the total river network, and
extending geographic protection to provide 20%
coverage would also require protection of the
mid-blue coloured planning units. The inclusion
of estimates of biodiversity condition is reflected
in the generally higher rankings given to good
condition planning units (Plate 18b, 19a), with
the top 10% of planning units having an average
condition of 0.71 compared with an overall average
for all planning units of 0.39. In addition, the
use of connectivity constraints clearly favours the
prioritization of interconnected sets of planning
units
Selection of high value sites for
conservation
High value sites - identified by selecting planning
units with high rankings (top 5%) nationally
or regionally, or for their ability to complement
currently protected planning units - are distributed
throughout New Zealand, but with a bias towards
planning units that are in good condition. Overall,
these high value sites contain approximately 8%
of New Zealand's river network, with a little
over half of the total area of these sites (53.3%)
already legally protected. The use of pragmatic
decisions in delineating some of these sites is clearly
from catchments having generally good
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