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Ecological classifications

New Zealand’s geography is highly variable, and its environment can change greatly over relatively short distances. However, geographically remote areas can have similar environmental characteristics (that is, similar climate conditions, landforms, and soils) that support particular ecosystems (habitats and species). These areas are said to be ecologically similar.

As an example, swampy areas on poorly drained recent soils in river valleys occur in many places between Gisborne and mid-Canterbury, although these places are geographically separate. Another example is the similarity of kiwi habitats, found in some parts of the North Island, South Island, and Stewart Island, even though these habitats are not geographically connected.

Once we have identified and mapped areas that have a similar ecological character, we can compare environmental data from these areas. This helps build a greater understanding of the state of New Zealand’s environment (Snelder et al, 2000), and helps decision-makers make appropriate environmental management decisions.

Environmental data from one area can also be used to extrapolate what might be happening in an area with similar ecological character, for which environmental data is not available. In this way, data from a limited number of monitored sites can be used to build a national picture of the state of the environment.

To identify, map, and extrapolate data in the ways described above, we use ecological classification systems. These systems compile information to identify and then map similar environments, biological regions, or land covers.

The five ecological classifications used in New Zealand for national state of the environment reporting are:

  • Land Cover Database series 1 and 2

  • River Environment Classification

  • Coastal and Marine Habitat and Ecosystem Classification System, comprising:

    • Coastal Biogeographic Regions Classification
    • Marine Environment Classification (which is not used in this report, but will be used for ongoing national environmental reporting)
  • Demersal Fish Community Classification

  • Land Environments of New Zealand.

A brief explanation of each classification follows. Technical information about the classifications can be found in Environment New Zealand 2007 – A Technical Guide to New Zealand’s Environmental Indicators (Ministry for the Environment, forthcoming).

Land Cover Database

The Land Cover Database series 1 and 2 is a geographically spatial (satellite) map of New Zealand’s land cover. Land cover describes the types of features present on the surface of the earth (for example, pastures, lakes, forests, or concrete).

Both database series are made up of 43 classes of land cover. This report uses these classes to monitor and report on the national environmental indicators for land cover, land use, soil intactness on erosion-prone hill country, and areas of land under legal protection.

The Land Cover Database series 2 is shown in Figures 1.2 and 1.3, with its 43 classes grouped into nine major land cover classes.

Figure 1.2: Land Cover Database series 2, North Island, 2002

Figure 1.2 is a map that shows the extent to which each of nine major land cover classes from the Land Cover Database Series 2 (2001-2002) cover the North Island of New Zealand.  The nine classes include: native forest, native vegetation, other native land cover (for example, alpine, ice and lakes), exotic forest, exotic vegetation, high producing exotic grassland and low producing grassland, primarily horticulture, and the last class, urban areas and artificial surfaces.

Figure 1.3: Land Cover Database series 2, South Island, 2002

Figure 1.3 is a map that shows the extent to which each of nine major land cover classes from the Land Cover Database Series 2 (2001-2002) cover the South Island of New Zealand.  The nine classes include: native forest, native vegetation, other native land cover (for example, alpine, ice and lakes), exotic forest, exotic vegetation, high producing exotic grassland and low producing grassland, primarily horticulture, and the last class, urban areas and artificial surfaces.

River Environment Classification

The River Environment Classification maps rivers that have a similar character across New Zealand’s landscape. Individual river sections are mapped according to physical factors such as climate, topography, and geology, and land cover conditions. Sections of river that have similar ecological characteristics can then be grouped together, no matter where they are (Snelder et al, 2004).

Figure 1.4 shows an image of the lower North Island. The coloured ribbons show the river network in these areas. The River Environment Classification identifies rivers according to their climate and source of flow. For example, the red rivers have a cool, wet climate and low elevation source, while the yellow rivers have a cool, wet climate and hilly source. ‘Other rivers’ includes several categories of climate and source of flow that have been combined for the purposes of this figure.

Different types of river respond differently to the pressures placed on them; the River Environment Classification can be used to highlight the most appropriate management tools and approaches to reduce these pressures for each river type. Information from the classification is used to develop policy, assess the environment, and report on the quality of river water.

Figure 1.5 shows the River Environment Classification for the river network in the Canterbury region. The rivers are divided into nine groups, according to the type of landscape they spring from (for example, a glacial mountain) and their underlying geology (for example, soft sedimentary rock). The key shows a colour code for each different river type.

Figure 1.4: Satellite image of lower North Island with rivers and streams overlaid using the River Environment Classification

Figure 1.4 shows a map of the bottom of the North Island of New Zealand as one solid colour, from about Palmerston North south.  Overlaid on the map are the rivers in this area shown in three different colours according to their river environment classification for climate and source of flow.  Rivers with cool, wet climate and low elevation sources and rivers with cool, wet climate and hilly sources are explained in the text. Other rivers are also showed on the map.

Figure 1.5: River Environment Classification of rivers and streams in the Canterbury region

Figure 1.5 shows a map of the Canterbury region in New Zealand’s South Island overlaid by its river network.  The river network is mapped according to the River Environment Classification for source of flow and underlying geology.  There are nine different types of river by their source of flow and underlying geology.  These are:

  • glacier mountain, hard sedimentary
  • mountain, hard sedimentary
  • hill, hard sedimentary
  • hill soft sedimentary
  • low elevation, hard sedimentary
  • low elevation, soft sedimentary
  • lake
  • spring
  • hill/ low elevation, volcanic.

The glacier mountain, hard sedimentary and mountain, hard sedimentary river types occur in the Southern Alps of the Canterbury region, with some of these river extending to the coast of the Canterbury region. The hill, hard sedimentary river type occurs predominantly at the base of the Southern Alps, with some rivers also extending to the coast of the Canterbury region. The river types between the base of the Southern Alps are predominantly low elevation, hard sedimentary and low elevation, soft sedimentary with some scattered springs and hill/ low elevation, volcanic river types.

Coastal and Marine Habitat and Ecosystem Classification System

New Zealand’s marine environment is characterised by sandy and rocky beaches, exposed cliffs, bays, and estuaries of varying sizes; and a variety of coastal and deep-sea habitats and ecosystems. Beneath the surface are diverse seascapes and plant and animal life.

Two ecological classifications for New Zealand’s marine environment have been developed and are used together for state of the environment reporting. The Coastal Biogeographic Regions Classification is used as a framework to provide information on the coastal marine environment (that is, waters less than 200 metres deep), and the Marine Environment Classification is used as a framework for deep-water environments (waters 200 metres or more deep) (Department of Conservation and Ministry of Fisheries, 2007; also see Figures 1.6 and 1.7).

Coastal Biogeographic Regions Classification

A biogeographic region is an area defined and classified according to visible ecological patterns and the physical characteristics of a geographic or hydrographic area. New Zealand is divided into 13 coastal biogeographic regions.

The Coastal Biogeographic Regions Classification (see Figure 1.6) can be used for assessing the health of the coastal marine environment, planning associated with marine protected areas, and reporting on the extent of marine reserves by ecosystem type within the territorial sea.

Figure 1.6: Coastal biogeographic regions to 12 nautical miles within New Zealand’s Exclusive Economic Zone

Note:

Although the boundary for the Coastal Biogeographic Region Classification is the 200 metre depth contour, planning for marine protected areas within each coastal biogeographic region only extends to the 12 nautical mile boundary. For this reason, each Coastal Biogeographic Region is mapped to 12 nautical miles in this Figure.

Data source: Department of Conservation and Ministry of Fisheries.

Figure 1.6 shows a map of New Zealand’s major islands in black surrounded by New Zealand’s 200 mile exclusive economic zone in blue.  The Coastal Biogeographic Regions are highlighted in two different colours around the edge of all the islands out to the 12 nautical mile boundary or outer limit of New Zealand’s Territorial Sea.  The 200 metre depth (contour) mark is shown in a separate colour where this occurs outside the boundary of a biogeographic region.

Marine Environment Classification

The 2005 Marine Environment Classification uses eight physical factors (for example, depth, sea-surface temperature, seabed slope, tidal current, and annual solar radiation) to classify and map marine areas that have a similar environmental character. The marine environments can be mapped to different levels of detail, ranging from two to more than 70 marine environment groups (Ministry for the Environment, 2005).

The Marine Environment Classification can be used at different levels for state of the environment reporting on deep-water environments to 200 nautical miles offshore (that is, the full extent of New Zealand’s Exclusive Economic Zone). Figure 1.7 shows the Marine Environment Classification at the 20-group level.

Demersal Fish Community Classification

The Demersal Fish Community Classification uses an extensive set of research data about trawling to model the distribution of 122 demersal fish species (species that live near the sea floor). This includes blue cod, hake, hoki, John dory, orange roughy, snapper, and tarakihi (Leathwick et al, 2006).

This research data was used to estimate the abundance of fish in each species across New Zealand’s entire Exclusive Economic Zone, including at sites for which trawl data was not available. These estimations enabled areas with a similar composition of species to be classified together.

The Demersal Fish Community Classification shows the geographic distribution of particular demersal fish communities, and describes their composition (the types of fish that live in the area) and the environmental conditions in which the fish occur. See chapter 11, ‘Oceans’ for an example of how the classification has been used.

Land Environments of New Zealand

The Land Environments of New Zealand classification maps areas of the New Zealand landscape that have a similar environmental character. It is used to identify areas that are similar, regardless of where they occur (that is, which areas are not necessarily the same in all respects, but are likely to contain similar species, and have similar biological interactions and processes) (Ministry for the Environment and Landcare Research 2002).

This classification differs from the Land Cover Database series 1 and 2 discussed earlier in this chapter. These simply identify land cover (what is growing on the ground or what feature covers the ground), whereas Land Environments of New Zealand uses 15 climate, landform, and soil factors that are considered likely to influence the distribution of animal or plant species. Based on these factors, land environments can be used as a surrogate for ecosystems.

Land Environments of New Zealand can be used at four levels of detail to map 20, 100, 200, or 500 land environments (see Figure 1.8). The higher levels provide greater detail by showing more land environments.

This classification is used to report on native biodiversity indicators. (See also Figure 12.2 in chapter 12, ‘Biodiversity’, which illustrates the mapping of 20 environments.)

Figure 1.7: Marine Environment Classification (MEC) at the 20-group level, 2005

Note: Because of the scale of this map, only 18 marine environments (18 different colours) are visible for the MEC 20-group level classification.

Data source: Ministry of Fisheries.

Figure 1.7 shows a map of New Zealand’s major islands in black surrounded by New Zealand’s 200 mile exclusive economic zone in 18 different colours.  Each colour shows the location of a different type of marine environment as classified by the Marine Environment Classification system at the 20-group level. 

The 18 marine environment types shown include:

  • three types of oceanic subtropical environments
  • four types of ocean, shelf, and subtropical environments
  • eight types of central coastal environments
  • three types of oceanic subantarctic environments.

Figure 1.8: Land Environments of New Zealand, Levels 1 to 4, showing mapping scales for 20 to 500 land environments

Figure 1.8 shows four different maps to illustrate the four different levels at which the Land Environments of New Zealand classification can be mapped. 

The first map, Level 1 of the classification, shows New Zealand’s North and South Islands to illustrate 20 different land environments and where these occur across New Zealand. 

The second map, Level 2, shows New Zealand’s North Island and 100 different land environments and where these occur. 

The third map, Level 3 of the classification, shows a portion of the Hawke’s Bay region to illustrate a 200 land environments classification. 

The fourth map zooms in on one area from the Hawke's Bay region to illustrate a 500 land environments classification. 

Each of the four maps illustrating the different levels of the classification uses a corresponding number of colours from 20 to 500 to classify and map the n