Native Habitats Tasman Ecological Assessment Report
Site: T 12
Landowners/Occupiers: Road Reserve; Common Marine & Coastal Area
Ecological District: Totaranui
Grid Ref: E2510711 N6017294
Surveyed By: Michael North
Date: 13 March 2014
Survey Time: 3 hrs
THE SETTING – TOTARANUI ECOLOGICAL DISTRICT (ED) Location and Physical Description
The Totaranui ED represents distinctive coastal granite country. Seventy per cent of the 26.5 thousand ha is included in the Abel Tasman National Park. Almost the entire district is composed of granite, apart from small areas of alluvium. The land forms a dissected tableland sloping from the highest points along the western boundary (Mt Evans, 1156m) to the north and east, so that most of the district is lowland. Steep small rivers drain the country, usually opening to estuarine inlets. The indented coastline has many headlands rock stacks and some small islands. The rainfall varies from about 4000mm at the highest points, to 1500 around much of the coast. The vegetation is mainly beech forest (black, hard, red and silver) with broadleaved species in the gullies and swampland in the valley floor. Much of the coastal vegetation has been cleared for farmland but most has regenerated to secondary forest. However farmland is present around the northern inlets and in the SE hills.
Totaranui Ecological District
Ecosystem types originally present
Apart from swampland (flax) behind dunes at the mouths of some valleys the entire district was originally forest covered. Forest was predominantly beech forest, silver beech at the highest levels, black beech over much of the lower slopes, red beech in the gullies and hard beech on the drier ridges. Gully beech forest was mixed with broadleaved species, especially northern rata, and podocarps, especially rimu. In the lower valleys the range of broadleaved species increased, mixed with podocarps such as rimu and kahikatea. Kahikatea swamp forest was present in the lower valleys. Estuarine vegetation bordered the inlets.
Existing ecosystems
The core of the district remains in original beech forest, and there are remnants of mixed broadleaved/podocarp forest in the valleys, although much of the original valley floor forest has
been removed and only small remnants and patches of swamp remain. Much of the original forest around the coast has been burnt and secondary forest dominated by tree ferns and kanuka covers large areas, especially in the north and south.
Degree of protection
Seventy per cent of the district lies within the national park and there are a number of other protected areas. There are significant natural areas of original forest remaining unprotected, and large areas of secondary forest are included in the national park.
Indigenous Ecosystems – Totaranui Ecological District
Ecosystem type Original
extent (% of ED)
Proportion of original
extent remaining
(%)
Proportion of original extent / remaining area protected
(%)
Original Remaining Coastal sand dune and flat
Estuarine wetland
Fertile lowland swamp and pond Infertile peat bog
Upland tarn Lake
River,stream and riparian ecosystems Lowland podocarp forest
Lowland broadleaved forest Lowland mixed forest Lowland beech forest Upland beech forest Subalpine forest Lowland shrubland
Upland/subalpine shrubland Frost flat communities Tussock grassland
Alpine herbfield and fellfield
3 5 0.4
- - - 1 1 - 20 40 20 - - - - - -
10 90 55 - - - 80
<1 - 1 60 95 - - - - -
-
8 72 50 - - - 80
<1 - .5 50 85 - - - - - -
80 80 90 - - - 100
5 - 50 85 90 - - - - - - [From Simpson & Walls (2004): Tasman District Biodiversity Overview’]
SITE DESCRIPTION
Location, Geology, Hydrology
This 2.3 ha site lies from just below Mean High Water to c30m asl. It occupies the saltmarsh margins of Tapu Bay estuary, and the steep landward slopes adjoining. The inlet is fed by a number of very minor streams.
The geology is Cretaceous Separation Suite biotite granite.
Vegetation C
OMMUNITIES Forest communities1 Black beech forest on coastal margin slopes 2 Hard beech forest on coastal margin slopes
Tracts of each species, as well as smaller areas of mixed beech are present. On this scale it is not surprising that there is no discernable difference of associates. Kanuka has a minor canopy presence. Young regeneration of fivefinger, with kanono and shining coprosma is typical. Where freer-draining, mingimingi is present, and Helichrysum lanceolatum and mapou are locally common. Kohuhu, inaka, and prickly mingimingi are occasional. Houndstongue fern is locally common. Other occasional species are inkberry, hanging spleenwort, and Uncinia banksii.
Minor gullies that lack beech punctuate the slopes. These are rich with ponga, along with mamaku, kanono, shining coprosma, and heketara, with very few ground associates.
3 Kanuka forest on coastal margin slopes
A small tract of well-packed pole kanuka is present at the northern end on gentle terrain above the coastal scarp. A few willow-leaved hakea trees are present close to the road. In parts there is a dense low regeneration of fivefinger, with occasional mingimingi, inkberry, gorse, and regeneration of mapou, kanono, and shining coprosma.
4 Fivefinger- mahoe forest on estuarine margin
A narrow tract of secondary broadleaved forest lies at the rear of the northern end of the saltmarsh into which it abruptly transitions. Ponga is present in the canopy and sub-canopy. Woody understories are largely of kanono and hangehange. Tutu, kamahi and makomako are rare. A few hen and chickens fern are present.
5 Black beech- kanuka- mahoe- fivefinger forest on coastal margin slopes
A tract of mixed forest occurs toward the southern end of the site; it was not traversed.13 Bracken fernland
Small areas of dense bracken occur within community 5.
Estuarine communites
6 Sea rush rushland 7 Oioi sedgeland
8 Batchelor’s buttons- marsh arrowgrass herbfield in stream deltas 9 Glasswort- sea primrose +- sea rush herbfield
10 Knobby clubrush- marram- tall fescue? sedgeland 11 Rautahi sedgeland
12 Three square sedgeland
Two small areas of saltmarsh comprising less than one hectare occur along the southern and central sections of the site. Oioi is the most dominant, with sea rush and three square common, either as pure mixed stands. Small areas of glasswort and sea primrose lawns are present locally.
Three small stream deltas support herbfields of batchelor’s buttons, marsh arrowgrass and Isolepis cernua. Rautahi (Carex geminata) forms very small swards at three locations on the interface of saltmarsh and higher land where groundwater seepage occurs.
Botanical Values C
OMMUNITIESLowland beech and beech-podocarp forest once covered nearly all of the Totaranui Ecological District (ED) below the treeline. Forest below 600m asl is defined as ‘lowland’ in the above table, which suggests that around 60% of the original lowland forest cover remains. Most of this is above 300m. The figure is far less for forest below 300m, although it is very difficult to calculate the original forest type cover due to extensive disturbance on a large and complex scale. It would appear that around 50% of land <300m is in forest (original and induced) – as interpreted from the Abel Tasman 1:50000 Parkmap. Probably <20% still remains in its original canopy cover, although this is speculative as it is likely that kanuka forest is both induced and also a common to dominant natural component of near coastal forest on the many free draining ridges.
90% of the original estuarine saltmarshes are estimated to survive within the ecological district (see table above), but only ever occupied 5% of the district. This site is one of the smallest, but is of note for having an unmodifed landward margin (ie lacks stopbanks and infilling), part of which is clad in native forest.
S
PECIES49 native plant species were noted. Marsh arrow grass and Isolepis cernua are localised within the ecological district, largely confined to the few estuarine saltmarshes that occur within the district.
Sand sedge is probably rare in the ecological district, occurring just outside the site on the adjoining largely weed-infested sandspit.
Fauna
Native forest birds noted were korimako/bellbird, riroriro/grey warbler and kotare/kingfisher.
Kingfisher nest holes were evident on vertical forest banks. Ruru/morepork, tui, piwakawaka/fantail, kereru/pigeon and waxeye are also known to be present in the locality and almost certainly use this site. Kotare nest-holes within the forest show that the site provides a nesting site for this species. No saltmarsh bird species were noted. It is possible that banded rail occupy the saltmarsh, at least seasonally. Shorebirds and waterfowl were noted within the inlet area outside the survey area, including low numbers of pied stilt, variable oystercatcher and grey teal.
Weed and Animal Pests
A range of exotic plants are present locally, with only jasmine of particular concern, as it is colonising the northern end of the forest, where it is still scarce. Gorse, broom, blackberry, willow- leaved hakea, marram and tall fescue all have a localised presence within the site. Crack willow margins to the saltmarsh have been excluded from the site.
Other Threats
Sea level rise threatens to extinguish the saltmarsh as the landward margins are steep, giving no options for inland retreat.
General Condition & Other Comments
The saltmarsh/inlet is largely unmodified. There is a minimal tidal influx other than at the higher tides, resulting in somewhat stagnating waters within the inlet. This appears to be natural, in no small part due to the small influx of freshwater from the few minor streams that feed into the inlet.
Native forest includes both young secondary forest around the northern half of the saltmarsh, and primary beech forest forming a coastal steepland ribbon to the north of this.
Landscape/Historic Values
Riwaka Inlet and Kaiteriteri Inlets lie c1km to the north and south (in a direct line). Native forest (Kaiteriteri Recreation Reserve, infested with wilding pines) lies across the road from the beech forest stand at this site. The site lies alongside the Riwaka-Kaiteriteri Rd.
ASSESSMENT OF ECOLOGICAL SIGNIFICANCE
The following criteria are assessed:
Representativeness: How representative is the site of the original vegetation? How representative is the site of what remains?
Rarity and Distinctiveness: Are there rare species or communities? Are there any features that make the site stand out locally, regionally or nationally for reasons not otherwise addressed?
Diversity and Pattern: Is there a notable range of species and habitats? To what degree is there complexity in this ie patterns and gradients?
Size/shape: How large and compact is the site?
Ecological context: How well connected is the site to other natural areas, to what extent does the site buffer and is buffered by adjoining areas, and what critical resources to mobile species does it provide?
Sustainability: How well is the site able to sustain itself without intervention?
Site Significance
The technical assessment is tabled in the Appendix.
This site is significant for the following reasons:
With moderately high representativeness values and high rarity values, there are sufficient scores for the site to be considered ‘significant’.
Management Issues and Suggestions
The forest lies within road reserve whilst the saltmarsh lies within the common marine and coastal area. For the sake of the future management and protection of the site it would be sensible to have the land above MHW springs vested in Tasman District Council, otherwise no-one is likely to take responsibility for it.
The main management issues relate to the removal of threatening weed species, most notably jasmine (invading into the northern-most margins) and marram along the saltmarsh margins particularly in the area where it competes with knobby clubrush.
Ideally the willows along the margins of the saltmarsh in its southern half could be removed and replaced with native forest species, whilst retaining a vegetated screen to miminize bird disturbance on the inlet from the new cycle trail and the road generally.
The interface of the saltmarsh and native forest supports a narrow band of intermittent gorse, blackberry and tall fescue. These could be sprayed out and planted with saltmarsh ribbonwood to restore the natural sequence from saltmarsh to coastal forest.
The Nelson-Tasman Branch of Forest and Bird has begun undertaking restoration of the almost wholly weed-infested sandspit that encloses the saltmarsh. To date this has entailed cutting/poisoning of gorse and some spraying of exotic iceplant. The restoration plan is to replace species such as gorse, tree lupin and exotic iceplant with native scrub/low forest. This will add considerably to the ecological value of the site in time. It is important that the sand sedgeland remains undisturbed during this process.
Coastal margin black and hard beech forest forms a ribbon along sections of the site
Saltmarsh grades into secondary forest at the back of the northern section of the inlet
A range of saltmarsh communities are present and several small creeks feed into it
A sea stack just offshore provides a seabird roost- here with white-faced heron and little shag
A narrow spit encloses the saltmarsh but it is clad almost entirely in exotic plants; it is subject to a native revegetation project by the local branch of Forest and Bird
Coastal margin black beech on a free-draining spur
Some sections of forest are lush with mixed broadleaved regeneration
Other areas are free-draining with sparser understories
Very minor gullies run down the slopes
Kotare nest holes in a forest bank
Hard beech with Dracophyllum filifolium
A very small stand of kanuka forest occurs in the northern corner beside the highway
The only area of native vegetation on the sandspit is this patch of sand sedge with shore bindweed
Crack willow lines the southern half of the estuary margin
Jasmine is invading the northern end of the forest from an adjoining garden
APPENDIX
Technical Assessment of Site Significance
Each site is ranked according to the highest ranking vegetation community or habitat that occurs within it. However, a site will be divided into more than one area for assessment purposes if they vary markedly in character, size or condition. Some examples are:
(a) a core area of vegetation (say, a podocarp gully remnant) is surrounded by/adjoins a much larger area of markedly different vegetation (say, kanuka scrub);
(b) a core area of vegetation has markedly different ecological values to the surrounding/adjacent vegetation;
(c) where artificially abrupt ecological boundaries occur between an area of primary vegetation and a surrounding/adjacent area of secondary vegetation - that is more than just a change in canopy composition.
The above does not apply if such adjoining vegetation forms only a small part of the total site, or if such vegetation forms a critical buffer to the core area.
Where such division of a site into two or more separately assessed areas occurs, such adjoining areas will also be considered in their buffering/connectivity roles to one another.
This site was assessed as one unit as the above considerations did not indicate the need to assess communities separately.
Significance Evaluation
Score Example/Explanation Primary Criteria
Representativeness
Primary vegetation or habitat that moderately resembles its original condition
MH Vegetation characterised by original canopy species and which has been only moderately affected by herbivores or direct human intervention: At this site the saltmarsh itself is largely natural and unmodified and lacks stopbanking on its landward side but with a native forest margin along only half of its length;
the northern section of beech forest is likely to be primary with at least a moderate resemblance to its original condition
Rarity and Distinctiveness A primary community (or mature secondary of the same defining canopy species) that is depleted to less than 20% of its original (pre- human) extent in the ecological district, in good condition
H Lowland forest <300m in the ecological district
An ecosystem that is originally rare and retains functional indigenous components
H Ecosystem types, as listed by MfE (2007) for protection as National Priority 3, e.g. saltmarshes Diversity and Pattern
Presence of a typical diversity of indigenous species, communities or habitat types for such sites in the ecological district
ML
Significance Evaluation
Score Example/Explanation Secondary Criteria
Ecological Context (highest score) Connectivity
The site lies close to other areas of indigenous vegetation
M Nearest saltmarsh lies 1km to the south and to the north-west; nearest native forest lies across the road (Kaiteriteri Recreation Reserve) from the forest at this site
Buffering to
Provision of critical resources to mobile fauna The site provides seasonally
important resources for indigenous mobile animal species and these species are present in the locality even though they may not have been observed at the site.
L e.g. Unusually important stands of podocarp, tawa or kowhai trees that provide seasonally important benefits for forest birds.
Size and Shape
A very small area for this type of vegetation or habitat for the ecological district
L
Other Criterion Sustainability (average score) ML
Physical and proximal characteristics Size, shape, buffering and
connectivity provide for a low overall degree of ecological resilience.
L Size ML Shape L Buffering L Connectivity M Inherent fragility/robustness
Indigenous communities are inherently quite fragile.
ML Saltmarsh fragile; black beech forest component inherently fragile due to dieback and rarity of regeneration in this locality
Threats (low score = high threat; lowest score taken) Ecological impacts of grazing,
surrounding land management, weeds and pests*
MH Grazing H Surroundings H Weeds MH Pests H
* observed pest impacts only
NB where scores are averaged, the score must reach or exceed a particular score for it to apply
Summary of Scores Criterion Ecological District
Ranking Primary Criteria Representativeness
Rarity and Distinctiveness Diversity and Pattern
MH H ML Secondary Criteria Ecological Context
Size and Shape
M L
Additional Criteria Sustainability ML
H = High MH = Medium-High M = Medium ML = Medium-Low L = Low
Summation of Scores to Determine Significance
If a site scores at least as highly as the combinations of primary and secondary scores set out below, it is deemed significant for the purposes of this assessment.
Primary Criteria Secondary Criteria
Any of the three primary criteria with a score at least as high as listed
Any of the two secondary criteria with a score at least as high as listed
Plus
H —
MH x 2 —
MH + M —
MH + MH
M x 2 + H
M x 2 + MH x 2
M + H + MH
H = High MH = Medium-High M = Medium
Is this site significant under the TDC assessment criteria? YES
Species List
r = Rare o = Occasional m = Moderate Numbers ml = Moderate Numbers Locally
c = Common lc= Locally Common f = Frequent lf = Locally Frequent x = Present But Abundance Not Noted P = Planted R = Reported
v= Very. For example: vlc = very locally common, mvl = moderate numbers very locally
Species Name Common Name Status
Land Environments of New Zealand (LENZ)
LENZ is a national classification system based on combinations of soil characteristics, climate and landform. These three factors combined are correlated to the distribution of native ecosystems and species.
When LENZ is coupled with vegetation cover information it is possible to identify those parts of the country (and those Land Environments) which have lost most of their indigenous cover. These tend to be fertile, flatter areas in coastal and lowland zones as shown in the map below for Tasman District.
Further information on the LENZ framework can be found at- www.landcareresearch.co.nz/databases/lenz
Location of Site YELLOW ZONE
National Priorities for Protecting Biodiversity on Private Land
Four national priorities for biodiversity protection were set in 2007 by the Ministry for the Environment and Department of Conservation.
National Priorities Does this Site Qualify?
1 Indigenous vegetation associated with land environments (ie LENZ) that have 20 percent or less remaining in indigenous cover. This includes those areas colored in red and orange on the map above.
No
2 Indigenous vegetation associated with sand dunes and wetlands;
ecosystem types that have become uncommon due to human activity
No
3 Indigenous vegetation associated with ‘naturally rare’ terrestrial ecosystem types not already covered by priorities 1 and 2 (eg limestone scree, coastal rock stacks)
No
4 Habitats of nationally ‘threatened’ or
‘at risk, declining’ indigenous species
No Further information can be found at -
www.biodiversity.govt.nz/pdfs/protecting-our-places-brochure.pdf
Significance of LENZ and National Priorities
What does it mean if your site falls within the highly depleted LENZ environments, or falls within one or more of the four National Priorities?
These frameworks have been included in this report to put deeper ecological context to the site.
They are simply another means of gauging ecological value. This information is useful in assessing the relative value of sites within Tasman District when prioritising funding assistance. They otherwise have no immediate consequence for the landowner unless the area of indigenous vegetation is intended to be cleared, in which case this information would be part of the bigger picture of value that the consenting authority would have to take into account if a consent was required.
