Extent of indigenous vegetation on land

Why we monitor the extent of indigenous vegetation

Areas of indigenous vegetation are an important storehouse of indigenous biodiversity. New Zealand is known internationally for its unusual plants and animals, many of which are found nowhere else in the world.

Loss of habitat, along with the introduction of animal and plant pests, has had a major role in extinctions and the high number of threatened species in New Zealand.

Even relatively recently, since the mid-1900s approximately 60 nationally threatened or at risk species have become regionally extinct, i.e. no longer present in Waikato Region. More than 300 indigenous species are known to be threatened with or at risk of extinction in the Waikato.

The areas of some ecosystem types, for example lowland forest and coastal forest, scrub and shrubland, have been reduced greatly - because the land they grow on is highly valuable for other uses such as farming or urban settlement.

Change in extent of indigenous vegetation means potential change in the diversity and security of native species.

Indigenous vegetation extent and distribution change indicates where natural areas have:

reduced - for example through clearance
increased - for example on retired land or as part of restoration efforts
changed - for example scrub and shrubland have developed into native forest.

Waikato Regional Council monitors changes in indigenous vegetation extent to provide information on where land use pressures are occurring, which vegetation and habitat types are at greatest risk of loss and for reporting on biodiversity. This helps us identify policy responses to avoid or reverse adverse effects on our biodiversity.

This indicator is restricted to terrestrial indigenous forest, scrub and shrubland and tussock grassland. Other natural areas in the region, including wetlands and coastal habitats, are reported in separate indicator report cards.

What's happening?

Before European settlement (around 1840) 94 per cent of the Waikato region’s land area (2396587 hectares, i.e. excluding Lake Taupo) was covered in terrestrial indigenous (native) vegetation, with the other 6 per cent being areas of wetland, bare rock, permanent snow and ice, or areas of Māori cultivation or inhabitation. Forest covered 53 per cent of the region. Scrub and shrubland or tussock grassland covered a further 41 per cent, mostly in areas where fires were frequent, or the land was too wet or cool for forest.

Change in land use, for example to agriculture, plantation forestry and urban settlement, required clearing indigenous vegetation. Today around 648,905 hectares (27 per cent of the region’s land area) remains in terrestrial (land-based) indigenous vegetation cover, mostly indigenous forest (19 per cent of the region), and scrub and shrubland (8 per cent).

The greatest loss of terrestrial indigenous vegetation since 1840 occurred in the central Waikato lowlands, around Hamilton City and in the Waipa, Waikato, South Waikato and Matamata-Piako districts where fertile soils on gentler topography were suitable for livestock farming, or where the hills were cleared for pine plantations. Districts with more rugged hill country and extensive ranges, such as Taupo, Otorohanga, Waitomo and Thames-Coromandel have a greater proportion of indigenous forest, scrub and shrubland and tussock remaining.

Coastal, lowland and sub-montane bioclimatic zones (below 800 metres elevation) lost the most indigenous cover, with around 70 per cent of the coastal and sub-montane zones and over 80 per cent of the lowland zone cleared for another land use.

In more recent times, the rate of indigenous vegetation loss in the region has slowed, as much of the productive land has already been cleared and 70 per cent of remaining indigenous forest set aside in reserves.

Since 1996, the Land Cover Database (LCDB) records an estimated net loss of around 530 hectares of indigenous forest and 1240 hectares of indigenous scrub and shrubland, along with a gain of 46 hectares of indigenous tussock grassland. Between 1996 and 2012 the region lost terrestrial indigenous vegetation at an average rate of 85 hectares per year.

Between 2012 and 2018 the net rate of loss dropped to around 60 hectares per year. In that time the Land Cover Database reports a net loss of 89 hectares of indigenous forest and 312 hectares of indigenous scrub and shrubland. The actual amount of indigenous forest loss is considered to be much less (around 14 hectares) based on a visual assessment of the LCDB polygons that changed from indigenous forest to another land cover type against time-series Google Earth images. Many of the cleared areas classified as indigenous forest were either exotic forest or an indigenous scrub and shrubland class in 2012.

The amount of scrub and shrubland lost since 2012, through clearance or natural causes such as fire, was 619 hectares, but this was offset by a gain of 307 hectares, mostly through natural regeneration in areas of former exotic forest plantation.

No gains in area of indigenous forest, or loss in area of indigenous tussock grassland were detected between 2012 and 2018. All of the losses and gains in indigenous terrestrial vegetation since 2012 were to or from a non-indigenous land cover, with losses mostly to pasture grass (80 per cent) or plantation forest (12 per cent).

The lowland bioclimatic zone experienced the greatest net loss of terrestrial indigenous vegetation (405 hectares). There was no measurable change in area of indigenous vegetation in the areas above 800 meters elevation (montane to alpine zones), while the submontane zone (300 to 800 metres) gained 66 hectares of scrub and shrubland, and 46 hectares of tussock grassland.

Ninety two per cent of the loss of indigenous forest, scrub and shrubland since 2012 was from four districts (Waitomo, Otorohanga, Waikato and Waipa). The Rotorua district had a net gain of 105 hectares of indigenous scrub and shrubland.

New Zealand has been divided into Threatened Environments, comprising 6 threat categories. Since 2012 most of the ongoing clearance in the Waikato region occurred in moderately (20-30% indigenous cover left) to less threatened environments (> 30 % left and > 20% protected), indicating either that there is greater protection for vegetation in the most threatened environments, or that there is very little vegetation left in those areas to clear.

While there was no measurable increase in the amount of indigenous forest in the region since 2012, over time it is expected to increase through natural maturation (succession) of areas of scrub and shrubland into forest. Conversely, the region is likely to see an ongoing decrease in the extent of scrub and shrubland vegetation over the coming decades because of the:

higher rate of clearance of scrub and shrubland compared with other native vegetation
lower proportion of scrub and shrubland in protected areas
natural maturation process of scrub and shrubland into forest.

However, restoration planting and retirement of unproductive land may offset this to some extent.

Methods - how we monitor

Monitoring sites
We measure indigenous forest, scrub and shrubland and tussock grassland vegetation for the entire Waikato region using the Land Cover spatial database which is based on satellite imagery. We report some of this at the district council level and by bioclimatic zone¹.
Monitoring frequency
Waikato Regional Council's monitoring of changes in indigenous vegetation is dependent on the release of updated LCDB layers by Landcare Research NZ. To date these releases have varied between four and seven years apart.
Historic (about 1840) vegetation extent is available as a single estimate of pre-European modification using the RIVI (Regional Indigenous Vegetation Inventory)².
Monitoring history
The LCDB (recent) data were derived from SPOT satellite imagery collected over five time periods:
- summer 1996/97
- summer 2001/02
- summer 2008/09
- summer 2012/13 and
- summer 2018/19
The RIV1 (1840) data were derived from:
- early settler accounts and maps
- early aerial photographs
- interpretation based on the current extent of indigenous forests.
Measurement technique
We used the:
- Landcover Database (LCDB Version 5.0 incorporating corrected versions of all previous LCDB layers) clipped to Waikato region land boundary to estimate the regional extent of indigenous vegetation during each LCDB time period and to assess change over time. The LCDB minimum mapping unit is 1 ha and the data are suitable for applications down to 1:25,000 scale.
- RIVI (1840) to estimate the extent of indigenous vegetation around 1840. The RIVI (1840) maps patches of vegetation to a nominal size unit of 50 ha for secondary vegetation and 25 ha for primary vegetation. Many patches below these limits were also included where their composition could be determined.
- Local authority boundaries 2019, (WRC Data layer name: POL_2019_REGIONAL_AUTH_NZ, source Statistics NZ).
- Waikato Bioclimatic Zones
Footnotes
1. Bioclimatic zones were developed for New Zealand (from international conventions) by Meurk (1984) and refined for the Waikato Region by Leathwick et al. (1995)
2. Leathwick, J. Clarkson, B. and Whaley, P. 1995: Vegetation of the Waikato Region: Current and Historic Perspectives. Landcare Research Contract Report LC9596/022. Landcare Research, Hamilton.

How this indicator is compiled

We used ESRI ArcGIS Pro and Microsoft Access software to calculate the extent of indigenous terrestrial vegetation within the Waikato region, and by district council area (2019 boundaries).

Gross change in indigenous vegetation extent since European settlement is calculated by comparing the RIVI (1840) data with commensurate vegetation classes in the LCDB. To achieve this, the RIVI (1840) indigenous vegetation classes have been combined into indigenous forest, scrub and shrubland and tussock grassland classes for comparison with the LCDB classes (see guidelines and standards below).

Guidelines and standards

For the current extent of indigenous vegetation the following LCDB classes are used:

Indigenous forest
Scrub and shrubland (aggregation of the following five LCDB classes: Broadleaved Indigenous Hardwoods, Fernland, Manuka and / or Kanuka, Matagouri or Grey Scrub and Sub Alpine Shrubland).
Tussock grassland (aggregation of the following three LCDB classes Tall tussock grassland, Depleted grassland and Alpine Grass/Herbfield)

The assumption is made that the scrub and shrubland classes and tussock grassland classes included in this indicator are either mostly indigenous in character, or will develop into mostly indigenous vegetation in a relatively short time.

The RIVI (1840) classification of vegetation types is aggregated into seven types comparable with the LCDC land cover classes. The table below shows the aggregated class name derived from the RIVI (1840).

Regional indigenous vegetation inventory	Aggregated class name
Beech forest	Indigenous forest
Coastal broadleaved forest	Indigenous forest
Conifer forest	Indigenous forest
Conifer-broadleaved forest	Indigenous forest
Conifer-broadleaved-beech forest	Indigenous forest
Kauri-conifer-broadleaved forest	Indigenous forest
Mixed conifer- broadleaved /conifer- broadleaved -beech forest	Indigenous forest
Mixed kauri/conifer-broadleaved forest	Indigenous forest
Mixed kauri/taraire/conifer-broadleaved forest	Indigenous forest
Montane conifer-broadleaved forest	Indigenous forest
Primary scrub and shrubland above treeline	Indigenous scrub and shrubland
Secondary vegetation on alluvial - Coromandel	Indigenous scrub and shrubland
Secondary vegetation on alluvial - Lower Waikato	Indigenous scrub and shrubland
Secondary vegetation on domes - Taupō Basin	Indigenous scrub and shrubland
Secondary vegetation on hillcountry - Coromandel	Indigenous scrub and shrubland
Secondary vegetation on hillcountry - Lower Waikato	Indigenous scrub and shrubland
Secondary vegetation on plateaux - Taupō Basin	Indigenous tussock grassland
Tongariro ringplain	Indigenous tussock grassland

This indicator is limited to the Waikato region. The Waitomo, Rotorua and Taupō districts all extend beyond the regional boundary. Therefore, Waikato Regional Council's information on this indicator may not be representative of the entire area of these three districts.
This indicator updates the previous indicator for extent of indigenous vegetation published by the Waikato Regional Council in 2015.
The 1840 vegetation map (RIVI) was created for the Waikato Region in 1994 based on the regional boundary at that time. In 2010 the region expanded northwards into part of the former Auckland Region, in accordance with the Local Government (Auckland Council) Act 2009, and for those newly acquired areas there is no 1840 vegetation data. This may slightly affect comparison with recent vegetation, however the changes have been so great any effect on the resultant data will be minor at the regional scale.
The LCDB gives a ‘snapshot’ of vegetation when the data were collected and should not be considered the definitive current vegetation cover. Data limitations also to consider are that all the framework datasets (e.g. Bioclimatic zones, Threatened Environments) used in the analysis have different boundary delineations. For example, the coastal boundary of the LCDB v5 dataset differs from the older 1840 RIVI vegetation map, and the local authority boundary layer. For the purposes of this analysis where possible the LCDB v5 boundary was used as the dominant boundary line. However, because the framework datasets are not all perfectly aligned to the current regional boundary, the total extent of a given vegetation type may vary when reported by different spatial frameworks. This is evident in the different total areas for indigenous forest when reported by local authority or bioclimatic zone in the data tables. However at the scale of the entire region the differences are insignificant.
Visual assessment of satellite images from circa 2019 and Street View images in Google Earth suggest that 22 of the 25 polygons reclassified from Indigenous forest in 2012 to another land cover type in 2018 were incorrectly classified in 2012. The actual amount of indigenous forest converted to another land use is thought to be around 14 hectares of the 89 hectares calculated using the LCDB Change layer. Many of the polygons are considered to have been exotic forest (mostly adventive pines) or an indigenous scrub and shrubland class (Manuka and/or Kanuka, or Broadleaved Indigenous Hardwoods). Therefore, the loss of Indigenous Forest is likely to be significantly overestimated based on the LCDB5 data. The visual check also involved checking for polygons incorrectly mapped as Indigenous Forest in 2019. Over 160 hectares of exotic forest, urban parkland or other classed mapped as Indigenous Forest was identified in a quick visual “sweep search” of the Waikato Region. Feedback on the incorrectly labelled polygons was provided to the LCDB developers. A similar exercise has not been conducted for the other indigenous vegetation classes.
Despite these potential errors, to provide for consistency nationwide, this indicator reports the current LCDB statistics, being the best data set available to the indicator compilers at the time.
The 1840 vegetation was mapped at a scale of 1:250,000, compared with the LCDB scale of 1:25,000 or greater. This means that many smaller areas of any given vegetation type will not be included in the RIVI (1840), but will have been aggregated into the local dominant vegetation type. For instance, the extent of tussock grassland is overestimated, as these areas were known to have patches of scrub and shrubland within them that have not been able to be mapped at that scale. Such generalisation of the vegetation types precludes analysis at finer scales such as bioclimatic zone for the 1840 data and only allows for gross level of change analysis. While there will be errors in comparing the databases, the changes between the two time periods (1840 and relatively recent) have been so great that they give a satisfactory indication of the regional gross change in vegetation since European settlement.
The RIVI and LCDB datasets use different vegetation classification systems. The Land Cover Database for instance has a single generic classification for indigenous forest, while the RIVI has a more detailed classification to forest type (for example, tawa-rimu forest, kahikatea forest). To allow for meaningful comparison between the 1840 and more recent databases, it has been necessary to aggregate vegetation classes to structure level (forest, scrub and shrubland and tussock grassland). This will also reduce inaccuracies from misclassification error, which is more likely to occur within a structural group than between vegetation structures.
Some vegetation classes can occupy terrestrial or wetland systems, e.g. flaxland, manuka, or fernland. In LCDB5 a “wetland context” field was added, allowing for separation of terrestrial from wetland areas of such vegetation. However, because the accuracy of the wetland context has not been tested in the Waikato, and for simplicity and consistency with earlier versions of this indicator, flaxland was treated as predominately wetland, and excluded from this indicator, while manuka and fernland were treated as predominantly terrestrial and included. Fernland is not structurally a scrub or shrubland class, however its amount is relatively small and being predominantly terrestrial has been included in the scrub and shrubland category. As a consequence of this decision, this indicator may slightly overestimate the extent of terrestrial forest and scrub and shrubland, however the proportion of manuka and or kanuka in a wetland context is less than 2 per cent in LCDB5, while the proportion for the other vegetation types is less than 0.3 per cent. These proportions were deemed inconsequential at the regional scale.
The LCDB ‘scrub and shrubland’ classes include areas of vegetation that are likely tall and mature enough to be considered forest, however the LCDB does not separate areas of Broadleaved Indigenous Hardwood that are forest from those that are scrub or shrubland. Broadleaved Indigenous Hardwoods are described in the Illustrated Guide to Target Classes for LCDB2 as being predominantly taller than 3 m. This would technically (per Atkinson 1985¹) make these polygons areas of indigenous forest. However the LCDB Illustrated Guide treats them as scrub and shrubland. To avoid confusion for future developers of this indicator, the Broadleaf Indigenous Hardwoods polygons were aggregated into the scrub and shrubland category.
Likewise, manuka is typically described (e.g. per Atkinson et al. 1985¹) as scrub or shrubland classes, while mature kanuka is typically a forest class. However these vegetation types are mapped as a single class under the scrub and shrubland category in the LCDB series and cannot be separated for this indicator. Therefore they have been treated as predominantly scrub and shrubland classes for the purpose of this indicator, and the current extent of scrub and shrubland is likely to be overestimated while the area of indigenous forest is likely to be underestimated.
Quality control procedures
For an updated description for the Land Cover Database (LCDB) v5, refer to the metadata descriptions and associated information that can be viewed and downloaded from the LRIS web portal.
For detail on the methods used to reconstruct 1840 vegetation in the Waikato region see Leathwick et al., 1995².
Further indicator developments
Waikato Regional Council has developed spatial layers of indigenous vegetation using aerial photography and a slightly simplified version of the LCDB classifications to improve our ability to monitor change in vegetation extent. The resulting layer is called Biodiversity Vegetation (Bioveg 2012). This layer, along with additional sources of information such as aerial oblique photos and more detailed vegetation maps generated for the Waikato Region biodiversity inventory project, are likely to provide more accurate and improved data sources for future iterations of this indicator.
The use of low level aerial oblique images will provide a greater level of accuracy and validation for vegetation classification. Future analysis and techniques using remote sensing and image object detection techniques will also aid in both the identification of vegetation types and measuring the rate of vegetation change and any potential vegetation loss.

Footnotes
1. A. E. Atkinson (1985) Derivation of vegetation mapping units for an ecological survey of Tongariro National North Island, New Zealand, New Zealand Journal of Botany, 23:3, 361-378
2. Leathwick, J. Clarkson, B. and Whaley, P. 1995: Vegetation of the Waikato Region: Current and Historic Perspectives. Landcare Research Contract Report LC9596/022. Landcare Research, Hamilton.

Results - data and trends

These data show that
- The proportion of the Region’s land area covered in terrestrial indigenous vegetation has decreased from 94 per cent in 1840 to 27 per cent in 2018.
- Since 1840 six local authority areas have lost over 80 per cent of their indigenous cover (Hamilton City, Matamata-Piako District, Rotorua District, South Waikato, Waikato District and Waipa District).
- There was a net loss of 89 hectares of indigenous forest and 312 hectares of indigenous scrub and shrubland from the region between 2012 and 2018.
- The rate of vegetation loss reduced from an average of 85 hectares per year between 1996 and 2012, to 60 hectares per year between 2012 and 2018.
- The greatest losses between 2012 and 2018 occurred in the lowland bioclimatic zone.
- Much of the recent clearance occurred in the less threatened environments, (areas with >20 indigenous cover left) with gains in the two most threatened environments – (areas with less than 20 per cent cover of indigenous vegetation).
Note: only a portion of the Rotorua, Taupo and Waitomo districts is in the Waikato region and the data may not be reflective of those districts as a whole. In 1840 up to 20% of the Hamilton, Hauraki, Waikato and Waipa districts were covered in wetlands (not reported on in this indicator).
Note: No change in terrestrial indigenous vegetation was measured in montane, subalpine or alpine bioclimatic zones between 2012 and 2018.

Change in area of indigenous vegetation cover by type between 2012 and 2018 within each Threatened Environment

Download the data file

The Excel spreadsheet below contains the source data for this indicator's graph and information.

The recent data (1996-2018) were sourced from the Landcover Database, collected from satellite image analysis.
Historic (1840) vegetation¹ was reconstructed in 1995 using settler accounts and maps, soil maps and interpretation based on current extent and early aerial photographs.

Leathwick, J. Clarkson, B. and Whaley, P. 1995: Vegetation of the Waikato Region: Current and Historic Perspectives. Landcare Research Contract Report LC9596/022. Landcare Research, Hamilton.

Download the data file
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More information

You can see how and where vegetation cover has changed over time using the New Zealand Landcover Explorer.

When this indicator is updated

The updating of this indicator is dependent on production of the updated LCDB. Because of the time scale at which vegetation change (other than clearance/drainage) occurs, it is unlikely that change will be monitored any more frequently than five yearly.

Data acknowledgements

The spatial data used in this project and dashboard includes:

1840 Vegetation for the Waikato Region. Leathwick, J. Clarkson, B. and Whaley, P. 1995: Vegetation of the Waikato Region: Current and Historic Perspectives. Landcare Research Contract Report LC9596/022. Landcare Research, Hamilton.
Land Cover Database version 5.0 (LCDB v5.0). Manaaki Whenua Landcare Research.
Territorial authority boundary 2020. Stats NZ.
Threatened Environments Classification 2012. Manaaki Whenua Landcare Research.

Category		Category Criteria
1		<10% indigenous cover left
2		10–20% left
3		20–30% left
4		>30% left and <10% protected
5		>30% left and 10–20% protected
6		>30% left and >20% protected

Extent of indigenous vegetation on land

Why we monitor the extent of indigenous vegetation

What's happening?

Methods - how we monitor

Monitoring sites

Monitoring frequency

Monitoring history

Measurement technique

Guidelines and standards

Results - data and trends

Download the data file

More information

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