**4. Freshwater wetlands**

Wetlands are defined as permanently or intermittently wet areas, shallow water and land water margins that support a natural ecosystem of plants and animals that are adapted to wet conditions. They support a wide range of plants and animals. In New Zealand, wetland plants include 47 species of rush and 72 species of native sedge (Johnson & Brooke, 1998). Many of these plants have very specific environmental needs, with a number of plants species adapted to wet and oxygen deprived conditions. Wetlands support a high proportion of native birds, with 30% of native birds compared with less than 7% worldwide (Te Ara – the Encyclopedia of New Zealand, 2009). For instance, the australasian bittern (*Botaurus poiciloptilus*), brown teal (A*nas chlorotis*), fernbird (*Bowdleria punctata*), marsh crake (*Porzana pusilla)*, and white heron (*Egretta alba*) rely on New Zealand's remnant wetlands. Migratory species also depend on chains of suitable wetlands. Wetlands are also an essential habitat for native fish, with eight of 27 native fish species found in wetlands (McDowall, 1975). Among those are shortfin eel (*anguilla australis*) and inanga (*galaxias maculatus*), the major species in the whitebait catch, and species from the Galaxiid family like the giant kokopu (*galaxias argenteus*), which is usually found in swamps (Sorrell & Gerbeaux, 2004). Apart from provision of habitat for biodiversity, wetlands offer other valuable ecosystem services such as flood protection, nutrient retention for water quality, recreational services (Mitsch & Gosselink, 2000), and important cultural services for Māori, including food harvesting and weaving materials. The importance of wetland ecosystems is recognised internationally, and New Zealand is a signatory to the Ramsar Convention on Wetlands of International Significance. Six sites are currently designated as Wetlands of International Importance, with a total area of 55 thousand hectares.

In less than two centuries, New Zealand wetlands have been severely reduced in extent, particularly with the conversion to pastoral agriculture from the mid 19th century. The loss is attributed to human activities through fires, deforestation, draining wetlands, and ploughing (Sorrell et al., 2004; McGlone, 2009). Further degradation of the habitat has occurred since the introduction of livestock with consequent increases in nutrient flows, changing the fragile equilibrium in the wetlands and altering species composition (Sorrell & Gerbeaux, 2004). The loss of local fauna and flora has also been dramatic. Fifteen wetland birds species have become extinct (with 8 out of 15 being waterfowl species) (Williams, 2004), and ten species are on the list of threatened bird species (Miskelly et al., 2008). Among the plants, 52 wetland taxa species have been classified as threatened (de Lange et al., 2004). The decline in many native freshwater fish is also attributed to the loss and degradation of wetlands (Sorrell & Gerbeaux, 2004).

Ausseil et al. (2011) estimated that the pre-human extent of wetlands was about 2.4 million ha, that is, about 10% of the New Zealand mainland. The latest extent (mapped in 2003) was estimated at 250,000 ha or 10% of the original coverage.

Continued impacts and reduced indigenous biodiversity are expected over the next century. In grazed areas, plant community composition should continue to alter gradually depending on stocking rates and variability in climate and disturbance regimes. As for areas that are completely converted to new land cover types, changes should be much more immediate. These conversions are likely to have significant impacts on the ecosystem

Wetlands are defined as permanently or intermittently wet areas, shallow water and land water margins that support a natural ecosystem of plants and animals that are adapted to wet conditions. They support a wide range of plants and animals. In New Zealand, wetland plants include 47 species of rush and 72 species of native sedge (Johnson & Brooke, 1998). Many of these plants have very specific environmental needs, with a number of plants species adapted to wet and oxygen deprived conditions. Wetlands support a high proportion of native birds, with 30% of native birds compared with less than 7% worldwide (Te Ara – the Encyclopedia of New Zealand, 2009). For instance, the australasian bittern (*Botaurus poiciloptilus*), brown teal (A*nas chlorotis*), fernbird (*Bowdleria punctata*), marsh crake (*Porzana pusilla)*, and white heron (*Egretta alba*) rely on New Zealand's remnant wetlands. Migratory species also depend on chains of suitable wetlands. Wetlands are also an essential habitat for native fish, with eight of 27 native fish species found in wetlands (McDowall, 1975). Among those are shortfin eel (*anguilla australis*) and inanga (*galaxias maculatus*), the major species in the whitebait catch, and species from the Galaxiid family like the giant kokopu (*galaxias argenteus*), which is usually found in swamps (Sorrell & Gerbeaux, 2004). Apart from provision of habitat for biodiversity, wetlands offer other valuable ecosystem services such as flood protection, nutrient retention for water quality, recreational services (Mitsch & Gosselink, 2000), and important cultural services for Māori, including food harvesting and weaving materials. The importance of wetland ecosystems is recognised internationally, and New Zealand is a signatory to the Ramsar Convention on Wetlands of International Significance. Six sites are currently designated as Wetlands of International

In less than two centuries, New Zealand wetlands have been severely reduced in extent, particularly with the conversion to pastoral agriculture from the mid 19th century. The loss is attributed to human activities through fires, deforestation, draining wetlands, and ploughing (Sorrell et al., 2004; McGlone, 2009). Further degradation of the habitat has occurred since the introduction of livestock with consequent increases in nutrient flows, changing the fragile equilibrium in the wetlands and altering species composition (Sorrell & Gerbeaux, 2004). The loss of local fauna and flora has also been dramatic. Fifteen wetland birds species have become extinct (with 8 out of 15 being waterfowl species) (Williams, 2004), and ten species are on the list of threatened bird species (Miskelly et al., 2008). Among the plants, 52 wetland taxa species have been classified as threatened (de Lange et al., 2004). The decline in many native freshwater fish is also attributed to the loss and degradation of

Ausseil et al. (2011) estimated that the pre-human extent of wetlands was about 2.4 million ha, that is, about 10% of the New Zealand mainland. The latest extent (mapped in 2003) was

structure and provision of ecosystem services.

Importance, with a total area of 55 thousand hectares.

estimated at 250,000 ha or 10% of the original coverage.

wetlands (Sorrell & Gerbeaux, 2004).

**4. Freshwater wetlands** 

Figure 4 compares the current extent of freshwater wetlands with its historic extent. The greatest losses occurred in the North Island where only 5% of historic wetlands remain compared with 16% in the South Island. The South and Stewart Islands contain 75% of all remaining wetland area, with the highest proportions persisting on the West Coast of the South Island and on Stewart Island. The remaining wetland sites are highly fragmented. Most sites (74%) are less than 10 ha in size, accounting for only 6% of national wetland area. Only 77 wetland sites are over 500 ha, accounting for over half of the national wetland area.

Fig. 4. Map comparison of current and historic extent of freshwater wetlands (blue areas) in New Zealand.

Classification of wetlands can be a challenge as they are dynamic environments, constantly responding to changes in water flow, nutrients, and substrate. Johnson & Gerbeaux (2004) clarified the definitions of wetland classes of New Zealand such as bog, pakihi, gumland, seepage, inland saline, marsh, swamps, and fens. By using GIS rules, it was possible to classify wetlands into their types and follow the trend of extent since historical times (Ausseil et al., 2011). Swamps and pakihi/gumland are the most common wetland types found in New Zealand. However, swamps have undergone the most extensive loss since European settlement, with only 6% of their original extent remaining (Figure 5). This is due to swamps sitting mainly in the lowland areas where conversion to productive land has been occurring. Unlike indigenous forest and indigenous grasslands, there is no national study describing recent loss over the last ten to twenty years for wetlands in New Zealand. However, some

Provision of Natural Habitat for Biodiversity: Quantifying Recent Trends in New Zealand 211

We used LENZ at level II (suitable for national to regional scale) and the most recent land cover (2008) to characterise historic and present habitats. The measure of habitat provision

*i i*

*ai* is the area of natural habitat remaining in land environment *i,* 

*Pi* is the biodiversity value of the *i*th land environment when fully natural.

*bij* is the area of of the *j*th habitat site in the *i*th land environment, and

*n* is the number of habitats in the *i*th land environment.

0.5. All other landcovers have a condition of 0.0.

habitat measure (i.e. each pixel represents

**5.2 Freshwater wetlands** 

*<sup>a</sup> H P*

0.5 *i*

0.5

(1)

(2)

*i*

*A* 

The 0.5 power index is used to produce a function monotonically increasing from zero to one with a decreasing derivative in order to represent the higher biodiversity value of rare habitat. In the absence of comprehensive and detailed biodiversity information, Dymond et al. (2008) suggested using species-area relationships (Connor & McCoy, 2001) to estimate *Pi* as the land environment area to the power of 0.4. The varying condition, or degree of naturalness, of individual sites also needs to be taken into account in the habitat measure:

> 1 *n ij ij j i i*

The condition of indigenous forest, subalpine shrublands, alpine habitats, and tussock grasslands above the treeline, are assumed to have a condition of 1.0. Tussock grasslands below the treeline have a condition of 0.8 and indigenous shrublands have a condition of

Figure 6 shows the input layers (current land cover and land environments at level II) and the resulting habitat provision map. This map shows the contribution per hectare to the

> *ij ij n i ij ij <sup>j</sup>*

*c b* 

Wetlands are at the interface between water and terrestrial dry environments. They have been categorised with freshwater environments in the past, and as such require a different definition of biogeographic units than the terrestrial environments. We replaced land environments data with biogeographic units defined by climatic and river basin characteristics (Leathwick et al., 2007). This framework was used to define priority conservation for rivers (Chadderton et al. 2004) and wetlands (Ausseil et al., 2011). A condition index for wetlands, similar to *ci* in equation (1), was calculated for all current wetland sites in New Zealand (Ausseil et al., 2011). This condition index reflects the major

*H*

).

*c b*

1

*<sup>A</sup> H P* 

*i c b*

**5.1 Indigenous forest and grasslands** 

for a land environment is defined as:

*Ai* the area of land environment *i*, and

where

where

*cij* is the condition,

Fig. 5. Current and historic extent of wetland per class.

regional analyses suggest that wetland extent continues to decline, although at a slower rate, as land drainage and agricultural development continue (Grove, 2010; Newsome & Heke, 2010). Wetland mapping is a challenging task as wetlands are sometimes too small in area to be identified using common satellite resolution. Their extent can vary seasonally (e.g., dryness, wetness) and therefore can change markedly at the time of imagery acquisition. While satellite images are useful for providing information at national scale, automatic classification is not possible as vegetation types in wetlands are so variable, making them difficult to characterise through spectral signature. Thus wetlands have been mapped on a manual or semi-automated basis (Ausseil et al., 2007), and this requires a significant amount of effort for all of New Zealand.
