EXECUTIVE SUMMARY: 1. Evidence based, landscape-scale assessments of biodiversity priority can play a valuable role
in assisting management agencies make informed decisions on which sites to protect or
manage, particularly when resources and funding are constrained. Such priorities have been
identified for the Northland Region, using spatial conservation prioritization software to
analyse high resolution data describing the distributions of indigenous-dominated terrestrial
ecosystems, rivers, and lakes. 2. Input data used in the ranking analysis comprised: a layer predicting the potential
distribution of terrestrial ecosystems across the entire Northland Region, including for sites
no longer supporting indigenous-dominated cover; the most recent version (4.1) of the New
Zealand Landcover Database (LCDB4.1); and, spatial data extracted from the Department of
Conservation’s Freshwater Ecosystems of New Zealand (FENZ) data compilation, describing a
variety of attributes for Northland’s lakes and for its river and stream network. Additional
data layers were constructed to describe the estimated condition of terrestrial sites, lakes
and rivers and streams. 3. The ranking procedure starts by assuming that the entire landscape can be
protected/managed; it calculates rankings using a stepwise backwards removal process, at
each step removing those sites making the lowest contribution to the representation of a
full range of ecosystems. This process continues until all sites have been removed, with the
removal order indicating the biodiversity ranking. For this analysis, connectivity constraints
encouraged the identification of high priority sites with strong connectivity both across the
landscape (terrestrial and lake ecosystems) and up and down river catchments (lakes, rivers
and streams). Weightings applied to terrestrial ecosystems during ranking resulted in higher
priority being given to ecosystems that have suffered greater losses in extent since human
settlement of the Region. 4. The top 30% of terrestrial sites identified from the analysis cover a total area of 133,545 ha,
equivalent to 10.6% of Northland’s pre-human indigenous terrestrial cover. This provides
representation of 83% for all primary ecosystems, on average; representation is inversely
proportional to ecosystem extent, with less extensive ecosystems having higher levels of
representation than those that are extensive. Kauri, podocarp, broadleaved forest, which is
currently the most extensive ecosystem, occupying 167,813 ha, has the lowest
representation within the top 30% of sites at 13.5% or 23,000 ha. 5. The top 30% of terrestrial ecosystems are distributed across 1293 locations, varying in size
between one and c. 25,500 ha; thirty-two exceed 500 ha in extent. Using a geographic
breakdown of the Region based on the New Zealand Ecological Regions, the largest number
of large priority sites, i.e., fourteen, are located in western Northland; six each occur in Te
Paki and Aupouri, while four occur in eastern Northland, and two in Kaipara. 6. Similar rankings are provided for rivers and streams, with the top 30% of the river network
providing representation of 19% or more for all river and stream ecosystems occurring
within the Region. Because of their discrete nature, a total of 88 individual lakes are
identified as priorities, these comprising 59% of all lakes by area. 7. Guidelines are provided to assist in the robust use of results to inform decision making.
