The main land use in the Dunedin & Coast FMU is plantation forestry (28%). A significant portion of this FMU is used for dry stock farming, including sheep and beef (19%), mixed sheep, beef and deer (4%), beef (5%) and sheep farming (8%). Dairy farming takes up close to 8% of the area, and around 7% is for urban use.   

Notable trends in land use change over the past 30 years are an increase in dairy farming by 38%, public conservation estate by 55%, plantation forestry by 19%, and urban land use by 4%. Dry stock farming has decreased by 14%, although it remains one of the main land use activities in the FMU.   

Brown soil covers 48% of the area, and Pallic soil covers 39%. This includes the north and south of Dunedin city and most of the Tokomairaro catchment. Brown soils are well-drained with moderate permeability and found mostly in plantation forests. Pallic soils have poor drainage and moderate to slow permeability and are mainly used for high-producing grasslands. Melanic soils are mainly around the Otago Harbour, are well-drained, and have moderate to rapid permeability.  

Dunedin & Coast land use summary

Surface water use in this area is relatively low. To the north of the FMU, Dunedin city water supply includes water take consents on the Leith and Waitati catchments, but these takes are now only for emergency supply and are not currently used. Most of the city’s water supply comes from the neighbouring Taieri FMU. In the southern part of the FMU, surface water is used for dairy sheds and stock water, mining and landfill activities, rural domestic water supply, and a small amount of irrigation.  

Water quality is monitored at eight river and stream sites, and ecological monitoring is at three river sites in the FMU. 

This monitoring shows high bacteria and nutrient concentrations at every site other than the Waitati River. Nutrient concentrations are highest in the urban streams. 

The Water of Leith, Kaikorai Stream and Tokomairaro all have degrading nutrient concentrations over the long term but have improved in the the last 10 years.  

Of the four sites monitored for aquatic health, two (Kaikorai and Lindsay’s Creek) do not meet the required standard for the Macroinvertebrate Community Index (MCI). This is likely to be because of the urban environment.  

Dunedin has large areas of hard surfaces for parking, which require a network of stormwater drains. These drains discharge contaminants, which often have high bacteria and nutrient concentrations, into local rivers and streams.  

Dunedin & Coast FMU Water Quality State and Trends Technical Report

LAWA Macroinvertebrate Community Index (MCI)

Introduction to water quality

Dunedin & Coast water quality summary

Groundwater use is low. The primary groundwater resource is the Tokomairaro Groundwater Management Zone, which is mainly used for domestic supply, stock water, irrigation, and dairy sheds. The consented allocation is a small proportion of the current Mean Annual Recharge. This FMU has only one monitoring bore, which generally shows good groundwater quality, with low E. coli and nitrates.  

Dunedin is known as the “wildlife capital of New Zealand” due to the rare and endangered species near the city and has areas of outstanding biodiversity, including the Otago Peninsula, a renowned wildlife and eco-tourism destination, and Orokonui Ecosanctuary, a wildlife reserve with rare species including forest birds, reptiles, and plants. 

Rare and threatened freshwater ecosystems within the FMU include lagoons, dune slacks, estuaries, and wetlands. These ecosystems are often threatened by land use change and invasive species. We know little about the extent and/or condition of these ecosystems.  

The Dunedin & Coast FMU has many species that depend on freshwater habitats, including fishes, invertebrates, plants and birds, among which are 44 threatened species. Native freshwater fishes are three non-migratory galaxias, four migratory galaxias (whitebait), two eel and five bullies. The lamprey and all non-migratory galaxias in this FMU are threatened.  

Freshwater invertebrates are koura, shrimp, and mussels. Threatened freshwater-dependent plants are Crassula peduncularis and Carex strictissima.  

Many native birds depend on freshwater ecosystems as permanent or mobile residents, including the threatened Australasian bittern and the at-risk black-billed gull. We lack information at a species level, particularly for freshwater invertebrates, non-vascular plants and algae.  

Exotic fishes are goldfish, perch and four salmonids. Many native freshwater species are under threat and continue to decline.  

Natural wetlands in the Dunedin & Coast FMU are mainly associated with estuaries and lower reaches of rivers and streams. Flaxlands are the most common wetland vegetation type with oioi restiad rushland widespread in coastal wetlands and carex in upland areas. The wetlands are generally small and scattered along water courses and around the coast. The Okia Flat wetland and the Tokomairaro River Swamp are the largest wetland systems, both over 170 hectares.  

Within the Dunedin & Coast FMU 16 sites are recognised as Regionally Significant Wetlands. These are presently classified as swamp (8 sites), several grading to salt marsh (2), marsh (4) and bog (1). 

Starting with the bog site, the flat crest of Swampy Summit (48 hectares) holds several tarns with margins of sphagnum bog grading to tussock and shrubland. The substrate is peat, which in places is exposed as dried, wind-eroded surfaces that reveal subfossil stumps of a former pink pine woodland, as well as quartz pebbles derived from moa gizzard stones. These are both indications of the bog’s history and changes over time for its flora and fauna.   

There are also bog communities in stream heads to the east of Swampy Summit, in basins that have up to six metres of peat, along with communities of sphagnum, carex sedgelands, mountain flax, surrounded by subalpine scrub and regenerating cedar cloud forest.   

One other bog site is recognised: Black Swamp, an isolated six hectare dome of peat on a ridge crest inland from Milton. This site has wire rush, sphagnum and sedge communities, and heath scrub of manuka and dracophyllum in surrounding farmland.   

Coastal wetland sites that have not yet been identified in the Dunedin & Coast FMU are those of Pūrākaunui Inlet and Blueskin Bay (including the Orokonui arm).  

The latitudinal distribution limits of plants are interesting – for example, species that are more common in northern New Zealand come south only as far as they can tolerate the cold, so sea rush (Juncus kraussii), reaches itssouthern limit in Pūrākaunui Inlet, and the tall sedge Bolboschoenus caldwellii at Tomahawk Lagoon.  

This FMU has seven estuaries, with natural or modified ecosystems depending on surrounding land use. The Tokomairaro and Kaikorai estuaries are the most affected by sedimentation and increases in nutrients due to upstream land use and are in a “fair” and “poor” state, respectively.   

The Kaikorai Estuary has experienced high modification and habitat loss due to urban development. The Blueskin Bay catchment is less modified, with native and plantation forests and low-intensity agriculture. Because of this, the estuary is in a “good” state, although it is vulnerable to habitat loss and modification of estuary margins.   

Papanui and Hoopers inlets both have large seagrass beds — a good sign of estuarine health. However, like all estuaries, they are susceptible to human activity and vulnerable to modification.  

The Dunedin & Coast FMU also contains several coastal lagoons. Little is known about most of these ecosystems. The Tomahawk Lagoon is a regionally significant wetland and wildlife sanctuary under stress from nutrient and habitat alteration. It experiences harmful algal blooms.