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No water no problem for mudfish Waiology Jun 10

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By Amber McEwan

While we head for the indoors as the weather grows colder and wetter, a secretive, little eel-like fish is gearing up for its busiest time of year.

Brown mudfish (Neochanna apoda).(Photo: Alton Perrie)

Brown mudfish (Neochanna apoda).(Photo: Alton Perrie)

The remarkable brown mudfish is one of five mudfish species that are all unique to New Zealand. They are small (up to around 15 cm), long and skinny and nocturnal. They live in wetland environments that tend to dry out in summer and survive these dry periods in a similar way to how bears survive the winter – they aestivate. To aestivate is to slow down your metabolism, burrow into the mud and hunker down until the rains come again. This way, the brown mudfish is actually able to survive out of the water for several months! When the autumn and winter rains re-flood the wetlands, it’s mudfish action time and these busy little fish come out of their slumber and begin looking for mates – although first, they probably have themselves a large breakfast!

Prior to European colonisation, vast tracts of New Zealand were seasonal wetland and mudfish would have been widespread. These days they are far scarcer, as over 95% of these wetlands have been drained to make way for agricultural and urban development. Historical accounts exist of people digging up recently drained fields of potatoes and finding aestivating mudfish still left alive from when the fields were wetlands – fish and chips!

Brown mudfish habitat. (Photo: Alton Perrie)

Brown mudfish habitat (Photo: Alton Perrie).

Brown mudfish are classed by the Department of Conservation as a declining species and remain in danger from further habitat loss along with introduced fish and weeds. Unlike most New Zealand freshwater fish, mudfish don’t need to migrate between freshwater and the sea in order to complete their life cycle so small groups of various mudfish species could be hanging on in remaining wetland fragments throughout New Zealand. If you have an area on your land that retains water in winter you might just want to take a torch out in the evening and have a look around – you may find mudfish!


Amber McEwan is a freshwater ecologist based in the Wairarapa

Wetlands series wrap-up Waiology Feb 08

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By Daniel Collins

Over the past two weeks we’ve had seven articles on wetlands from across New Zealand’s research and management communities. The occasion was World Wetlands Day on February 2. The articles provided a great cross-section of analysis on how we perceive, preserve and study wetlands. Here is a summary:

Catherine Knight, from Massey University, started the series with an historical account of wetlands in New Zealand and changes in perceptions, language and landscapes.

Philip Grove, from Canterbury Regional Council, shared results of a study of Canterbury’s coastal wetlands – their composition, state, and pressures.

Shonagh Lindsay, from the National Wetland Trust, described the National Wetland Trust’s project taking shape around Lake Serpentine – the Trust’s new centre, educational facilities, and restoration efforts.

Dave Campbell, from University of Waikato, described research on the carbon balance of peat wetlands.

Daniel Collins, from NIWA, put wetlands into the water cycle, combing natural history with etymology.

Hugh Robertson, from the Department of Conservation, described the conservation of internationally important wetlands within New Zealand.

Bev Clarkson, from Landcare Research, concluded the series by giving an overview of the research on wetland restoration in New Zealand.

I hope you have enjoyed the articles and learned a lot – please tell us how you thought the series went. And if you have any questions about wetlands, requests for more articles, or your own insights, please make a note of them in the comments below – hopefully the series authors or audience members can weigh in.


Dr Daniel Collins is a hydrologist and water resources scientist at NIWA.

Progress in restoring wetlands in New Zealand Waiology Feb 07

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By Bev Clarkson

The wetland restoration handbook is available free online at http://www.landcareresearch.co.nz/services/biocons/wetlands/.

New Zealand wetlands sustain indigenous biota, improve water quality, abate floods, lock up carbon, and provide cultural, recreational, and educational resources. Despite their multiple values, more than 90% of pre-settlement wetlands have been lost. Remaining wetlands are under increasing pressure through too little water, too much nutrient, and too many weeds and pests, and many require urgent action to prevent further loss and degradation.

Landcare Research and its research partners NIWA, DOC, University of Waikato, and Waikato Raupatu River Trust have worked to deliver scientifically based guidelines, techniques, and tools to improve the management and guide the restoration of wetlands. These improve the likelihood of success in repairing complex physical–biological processes, and thus reduce the risk of wasted time or resources. Publication of our wetland restoration handbook (Peters & Clarkson 2010) represents the culmination of many years of research that involved development of best practice techniques from restoration experiments, case studies, and collaboration with wetland partners and the wider community.

Bamboo rush bog ready to be showcased to the public at the proposed National Wetland Centre, Lake Serpentine.

Restoration techniques were developed through field experiments in wetlands that have been drained, burnt, mined, invaded by weeds, or otherwise modified. These experiments include restoration of a rare and threatened bamboo rush (Sporadanthus ferrugineus) bog type at a site that is being mined for horticultural peat. When the bogs are restored using our patch creation approach, nutrient balances are improved, leading to faster growth rates, improved decomposition patterns, and increased storage of carbon. Under our technical guidance, wetland managers and community groups have introduced populations of bamboo rush and rare invertebrates to three new wetland projects at sites where the bog type once occurred – Lake Serpentine, Lake Komakorau, and Waiwhakareke Natural Heritage Park, in the Waikato. The bamboo rush bog at Lake Serpentine will be showcased as part of the soon-to-be-built National Wetland Trust’s wetland interpretation centre.

Scott Bartlam, Landcare Research, sampling a nutrient enrichment plot at Toreparu Wetland, Waikato.

Our current research focuses on determining hydrological and nutrient thresholds to maintain indigenous biodiversity and functioning. This research includes a nutrient enrichment experiment across a swamp-fen-bog wetland gradient, which indicates that high inputs of phosphorus (e.g. from fertiliser drift) can threaten our unique bog ecosystems by inhibiting the formation of peat-forming roots. Another experiment on litter decomposition shows even a small lowering of the water table in wetlands can exponentially increase litter decomposition rates. This indicates the integrity of wetlands, particularly those in extensively developed landscapes, is being threatened by on-going regional lowering of water tables. On-going drainage can also lead to significant increases in the release of carbon, thus contributing to global warming.

The goal of our research is to increase the number and success rate of wetlands being restored by providing a sound foundation for their management, monitoring, and restoration. By working alongside DOC, local authorities, iwi, and the wider wetland community we will help achieve New Zealand’s high-level goals of protecting wetland biodiversity values.

References

Peters M, Clarkson BR eds 2010. Wetland restoration: a handbook for New Zealand freshwater systems. Lincoln, Manaaki Whenua Press. 273 p.


Dr Bev Clarkson is a plant ecologist at Landcare Research, Hamilton, and leads the MBIE-funded Restoring Wetlands programme under contract C09X1002.

Ramsar wetlands in NZ: Why are they important and where are we going? Waiology Feb 05

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By Hugh Robertson

The Ramsar Convention on Wetlands is a global environmental treaty that “provides the framework for national action and international cooperation for the conservation and wise use of wetlands and their resources”. The Ramsar Convention was established in 1971, in the city of Ramsar, Iran.

Awarua wetland Ramsar site, Southland. Source: DOC.

New Zealand became a signatory to the Ramsar Convention in 1976, in the initial cohort of members. Nowadays, there are 164 countries committed to the Ramsar Convention – a truly international community.

A key focus of the convention is to designate Ramsar sites – wetlands of international importance, and more generally to improve the management of all wetland systems. Globally, there are over 2000 Ramsar wetlands, covering 204,700,000 hectares.

The same year NZ signed the convention, our first wetland became listed as one of international importance: Waituna Lagoon, Southland (3,556 ha). Since then a further five sites have been listed (Table 1). Waituna Lagoon has also expanded to form the broader Awarua wetlands Ramsar site of 18,900 ha, our largest Ramsar site.

The NZ sites are special. The mudflats of Farewell Spit, for example, support an immense biomass of invertebrates, birds and fish – with flow on benefits across Golden Bay (and wider). Waituna Lagoon is of high cultural significance and the Firth of Thames is a critical site for migratory species (Table 1). Recognising their Ramsar status also takes account of the ecosystem services that wetlands provide society, whether in the form of fisheries production, reducing flooding or tourism (PDF).

NZ Ramsar site Known for Area (ha) Date listed
Awarua wetlands, incl. Waituna Lagoon Extensive, intact peatlands, estuary, coastal lake. 18,900 1976
Farewell Spit Expansive mudflats and sandspit, high bird diversity, migratory species. 11,400 1976
Manawatu Estuary Important feeding ground for migratory species. 200 2005
Whangamarino wetland Very large raised peat dome/swamp complex. Australasian bittern stronghold. 5,900 1989
Kopuatai Peat Dome Largest raised peat dome in North Island, peat-forming Sporadanthus (rare bog plant). 10,200 1989
Firth of Thames Shell banks, tidal mud and sand flats offer extensive feeding for wading birds and waterfowl. 7,800 1990

*For more information, see the DOC website.

The global vision of the Ramsar list is to “develop and maintain an international network of wetlands which are important for the conservation of global biological diversity and for sustaining human life”. To achieve this, the Ramsar Convention has published a strategy (PDF) that recommends the development of “national networks of Ramsar Sites… which fully represent the diversity of wetlands”.

In a NZ context, I am often asked what the value of Ramsar status is. A typical question is, “isn’t our effort better invested in improving catchment management, or developing a fully representative network of protected areas such as covenants and national parks?”

My response is that the value of Ramsar listing is to significantly increase the international and national awareness of our most ecologically significant wetland ecosystems. The long-term benefits of having elevated community and stakeholder awareness can be hard to predict, but should not be underestimated. Ramsar status may also lead to the investment of more resources from government agencies, NGOs, business partners, community groups and iwi. While Ramsar sites are not closely aligned with any particular legislation, all NZ Ramsar sites (with the exception of Manawatu Estuary) are listed in Schedule 4 of the Crown Minerals Act, and are therefore closed to mining.

The Department of Conservation has outlined future priorities for implementing the Ramsar Convention – including developing a more strategic approach to site nomination. Guidelines on what constitutes ‘internationally significant’ within a NZ context are in review.

Ramsar sites in waiting. Wetlands such as those within O Tu Wharekai (Ashburton Basin) may make complementary additions to the Ramsar network. Source: H. Robertson (DOC).

Once a site becomes a Ramsar wetland, maintaining their condition is a priority. DOC recently produced a national report summarising the condition of our six sites. Overall, there was little change in their ecological state over the past four years. Some wetlands showed improvement, for example through wide-scale invasive plant control, while others (Whangamarino, Waituna Lagoon) were under threat from declining water quality [1][2]. Initiatives such as the DOC Arawai Kakariki wetland restoration programme [3] and the efforts of community groups continue to help maintain these internationally significant ecosystems.

World Wetland Day provides an opportunity to recognise the successes of what Ramsar has achieved since 1971, and to reflect on both the positive and challenging issues relating to water management. For me, this includes recognition that New Zealand has come a long way since becoming a signatory to the Ramsar Convention in 1976, and an appreciation that 164 countries are able to reach agreement on global issues such as climate change and water (PDF) – yet recognising that many of our freshwater ecosystems remain under threat.

References:

[1] Blyth, J.M. (2011). Ecohydrological characterisation of Whangamarino wetland.Master of Science (MSc) Thesis, University of Waikato.

[2] Robertson H.A. and Funnell E.P. (2012). Aquatic plant dynamics of Waituna Lagoon, New Zealand: trade-offs in managing opening events of a Ramsar site. Wetlands Ecology and Management 20: 433-445.

[3] Robertson H. and Suggate R. (2011). Arawai Kakariki wetland restoration programme 2007-2010: Implementation report. Department of Conservation, Christchurch.


Dr Hugh Robertson is a wetland ecologist with the Department of Conservation. He is the STRP (Science and Technical) National Focal Point for the Ramsar Convention in NZ.

What makes wetlands wet lands? Waiology Feb 04

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By Daniel Collins

The simple answer is, of course, water. But that says little about the natural history of wetlands, or what physical conditions are necessary to maintain, restore or even engineer them. For that, we need to take a closer look at wetland hydrology.

Wetlands are tracts of land that are water-logged at least seasonally. They may be spongy bogs, mountain tarns, verdant swamps, or many other types. They remain wet because the inputs of water from rain, rivers or groundwater compensate any losses.

The various types can be distinguished based on their hydrology. In their book on wetland restoration, Bev Clarkson and Monica Peters (2010) quantify this continuum with the “gumboot test”. Short “red bands” are usually okay for keeping you dry in bogs, taller gumboots are needed for fens, thigh waders for swamps, and waist waders for marshes.

The continuum of wetland types in New Zealand, after Clarkson and Peters (2004).

A kettle hole at O Tu Wharekai/Ashburton Lakes. Kettle holes, formed by glacial deposits, are fed by rainfall and groundwater and can fluctuate from wet to dry depending on groundwater levels. (Photo: M. Beech, DOC)

Controlling this water balance are climate, geomorphology and even the vegetation itself. Wetlands typically form in gently sloping or topographically convergent portions of a landscape, where surface and ground waters meet. The vegetation plays several roles here, including the build-up of peat, changing evaporation and water flows, and by controlling erosion and hence the shape of the local landscape to some degree. Kettle holes, such as those in the Ashburton Lakes, are an example of the climate and glacial geomorphology controlling the hydrology, which in turn controls the ecology.

Each plant species is adapted to a particular range of wetting and drying. Too dry for too long, and terrestrial plants can invade. This is particularly important to bear in mind when conserving, restoring or engineering wetlands. It’s not enough to simply add water – the hydrological regime must match the desired ecosystem’s needs.

Some of the hydrological effects of wetlands are in essence also ecosystem services – benefits conferred to society by the wetlands. Reducing flooding and augmenting low flows are two services often cited, though they are not true for all wetlands (Bullock and Acreman, 2004). Science is actually a little in the dark as to which biophysical features of wetlands confer or degrade the various hydrological services.

And as we consider the hydrological origin of wetlands and differences between wetland types, it is also interesting to consider the etymological origin of wetland words. The word “swamp”, for example, can be traced back to the Old Norse word for “sponge”, sharing a common ancestry with “sump”. “Marsh”, “morass” and possibly “moor” have origins in the Proto-Germanic word for “sea”, and are in turn related to the words “marine” and “maritime”. “Mire” comes to us from the Proto-Indoeuropean (PIE) word for “damp”, and shares this root with “moss” and “must” (as in “musty”). “Bog” came to us via Gaelic, with a meaning of “soft” or “moist”, and earlier still from the PIE word for “bend” (as does “bow”). And lastly “fen”, which remains truest to its roots, goes back to the PIE word for “swamp”.

Ordering these words on a scale from less to more wet, in terms of their etymological roots, we get: bog – fen/swamp – mire – marsh. As a testament to biophysical basis of words, this aligns nicely with the order of wetland types illustrated above.

Much, however, remains to be learned about the hydrological origins, needs and impacts of wetlands. Continued research in this front will assist in conservation and restoration, the use of ecosystem services, and in the broader understanding of the water cycle – all very useful as NZ seeks to balance resource use with environmental protection.

References:

Bullock A. and Acreman M. (2003). The role of wetlands in the hydrological cycle. Hydrol. Earth Syst. Sci., 7, 358-389, doi:10.5194/hess-7-358-2003.

Clarkson B. and Peters M. (2010). Wetland types. In B. Clarkson and M. Peters, eds., Wetland restoration: A handbook for New Zealand freshwater systems. Manaaki Whenua Press, Lincoln. Pp. 273.


Dr Daniel Collins is a hydrologist and water resource scientist at NIWA.

Happy World Wetlands Day! Waiology Feb 02

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By Daniel Collins

Halfway through Waiology’s series for World Wetlands Day we’ve already learned a lot about New Zealand wetlands and efforts to study and restore them. But today being the day, how about you actually visit one? I’ll be at Christchurch’s Travis Wetland. And then come back for more articles in the coming week. In the meantime, here is a buoyant cartoon from Ramsar.


Dr Daniel Collins is a hydrologist and water resources scientist at NIWA.

Why measure carbon budgets in NZ peat wetlands? Waiology Jan 31

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By Dave Campbell

In 1769 Captain James Cook’s Endeavour anchored at the mouth of the Waihou River near the present-day town of Thames. Cook’s naturalist, Joseph Banks, was impressed by the evident resources within the vast swamp forest that covered the lower Hauraki Plains:

…The Noble timber, of which there is such an abundance, would furnish plenty of materials either for building defences, houses or Vessels.

…Swamps which might doubtless Easily be drained, and sufficiently evinced the richness of their soils by the great size of the plants that grew upon them, and more particularly of the timber trees which were the streightest (sic), cleanest, and I may say the largest I have ever seen…

Aerial view of the south eastern portion of Kopuatai bog, Mt Te Aroha in the distance. In the foreground is Empodisma robustum rush-land, the red-tinged vegetation in middle distance is the world’s largest remaining stand of Sporadanthus ferrugineus.

The great Kahikatea forests that so impressed Banks have now been replaced by farms where dairy cows graze on lush grass growing on the drained swamp soils. However, beyond the farms still lies a huge wetland that has somehow survived the early attempts to drain it. Kopuatai, at 90 km2 in area, is NZ’s largest remaining raised peat bog and one of our largest lowland wetlands.

Kopuatai bog has vegetation that is completely unique compared to the bogs of the northern hemisphere, where peat formation is dominated by mosses. In NZ, peat is predominantly formed from the remains of vascular plants of the southern hemisphere family Restionaceae. Two species, the wire rushes Empodisma robustum (north of 38oS) and E. minus (south of 38oS) are the main peat-formers[1], while Kopuatai bog is the last secure stronghold for the taller cane rush Sporadanthus ferrugineus.

Amid global concerns about rising atmospheric greenhouse gas concentrations and growing evidence that a warming climate is directly linked to human activities, the world’s peatlands are gaining increasing attention from scientists. Since the end of the last ice age, plants growing within peat wetlands (bogs and fens) have been taking up CO2 from the atmosphere and storing it underground as peat. Northern hemisphere peatlands alone store around half as much carbon as is presently in the atmosphere as CO2, so it’s understandable why scientists are concerned about what might happen to all of this stored carbon in the future[2].

While the world’s peatlands have been net “sinks” for CO2 for millennia (they take up more CO2 than they release), they also act as sources of methane (CH4), a greenhouse gas around 21 times more potent at trapping heat in the atmosphere than CO2. To find out whether peatlands have a net cooling or warming effect on the climate system, now and projected into the future, requires scientists to compile “net ecosystem carbon budgets” over annual and longer periods. This approach provides the opportunity to understand the environmental conditions and ecological properties that affect the components of these budgets, and how they might change in the future.

Kopuatai research site. On the tall tower are mounted eddy covariance instruments measuring CO2, CH4, water vapour and heat exchanges between the bog vegetation (predominantly E. robustum) and the atmosphere.

We have been slow to gain information on the carbon budgets of NZ peatland ecosystems and therefore we have been unable to predict how they might change in the future. To fill this knowledge gap we have established a research site deep in the heart of Kopuatai, where we are continuously measuring the exchanges of CO2 and CH4 between the peatland surface and the atmosphere, as well as a host of hydrological, ecological and weather variables. We are using the “eddy covariance” technique, which is employed at more than 500 sites worldwide across a wide range of ecosystems. Kopuatai is part of the “OzFlux” network of Australasian research sites. Our preliminary results suggest that Kopuatai bog has very high rates of CO2 uptake compared to analogous northern hemisphere peatlands, mainly because of the mild year-round growing conditions in the Waikato. Methane emissions are moderately low, and the amount of dissolved carbon leached out by water is in line with northern bogs. Combining these three carbon budget components at Kopuatai leads to a substantial overall sink for atmospheric carbon over the course of a year.

Our research will provide important baseline knowledge to support efforts to restore NZ wetlands and act as a yardstick against which to compare the greenhouse gas balances of other wetlands and former peatland areas that are now farmed.

References

[1] Wagstaff, S, Clarkson, B. 2012. Systematics and ecology of the Australasian genus Empodisma (Restionaceae) and description of a new species from peatlands in northern New Zealand. PhytoKeys 13: 39-79.

[2] Limpens, J, Berendse, F, Blodau, C, Canadell, JG, Freeman, C, Holden, J, Roulet, N, Rydin, H, Schaepman-Strub, G. 2008. Peatlands and the carbon cycle: from local processes to global implications–a synthesis. Biogeosciences Discussions 5: 1379-1419.


Dr Dave Campbell is a Senior Lecturer in the Department of Earth and Ocean Sciences at the University of Waikato. To see his research interests, visit www.waiber.com.

World Wetlands Day at Lake Serpentine, site for proposed National Wetlands Centre Waiology Jan 30

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By Shonagh Lindsay

The Rotopiko/Serpentine complex, a headwater of the Waikato River at Ohaupo south of Hamilton, is steadily being developed by the National Wetland Trust as the site of New Zealand’s National Wetland Centre, a showcase for wetland education, training and research. To celebrate World Wetlands Day, the Trust will launch work on the National Wetland Centre on Sunday 3rd February. A blessing by local iwi and brief addresses will be followed by a range of family fun activities that reflect the vision to create a ‘masterpiece’ at this beautiful site.

Collecting insect samples.

The Trust has so far received significant funding to develop a predator-free wildlife sanctuary and restore vegetation in the peat lake/swamp forest complex. Getting the local community involved is integral and last year the lake area became a hive of forensic activity as Te Awamutu Intermediate students went on the hunt for native and introduced fauna, laying a network of insect traps, tracking tunnels, bat detectors and lizard homes to find out what lives in the reserve complex.

The lakes and their margins are managed by the Department of Conservation, while adjacent mature kahikatea swamp forest and former pasture land are recreation reserve areas managed by the Waipa District Council. Ecological values are already high with the lakes’ water quality amongst the best in the region, and the restoration work underway and planned will ensure it remains so. It is one of a very few remaining peat lake systems in the region that has retained many of its unique characteristics and spectacular native aquatic plant communities. The lake margins have well-established reed beds, sedgelands, and an area of the rare, peat-forming, giant cane rush – Sporadanthus ferrugineus.

Kahikatea bordering East Lake,

Long and short-finned eel, common bully and a lake-bound population of smelt are present, along with fourteen species of water birds including Australasian bittern, North Island fernbird, and spotless crake. Hopefully their numbers will grow once pests are gone from East Lake, and if community-led pest control in the wider catchment provides a halo of safe habitat for those that choose to fly over the fence. Brown teal and red-crowned parakeets could be introduced to the pest-free enclosure, which may also become a kiwi creche and house display takahe. Lizards and bats may already be present, and the Trust hopes that further surveys will detect them.

Interpretation will be an essential part of the National Wetland Centre’s experience. Pearson & Associates Architects have been commissioned to design the Centre building, which will serve as a hub for interpreting the big picture – New Zealand’s wetlands in a national and international context – and become a base for educational programmes. Designed to fit into the landscape it will become part of the whole conservation experience as well as serving as an administrative centre for the National Wetlands Trust.

A series of wetland ‘gardens’ that illustrate the range of wetland types found in New Zealand – estuary, red tussock, alpine tarn, geothermal, braided river – will be integrated into a walkway to the building’s location to create a virtual sea to mountain journey. The peat lake itself is the perfect setting to tell the regional wetlands story, and will be integrated into the overall interpretation with walkways, signs and structures to inform and delight.

As the pace of activity cranks up the need for volunteers is growing. The Trust would love to hear from you if you want to be part of this exciting project. Not only will you be contributing to a great cause, but you can meet like-minded people and learn some great skills. You don’t have to be a local either – there’s plenty of scope for anyone to help out with education and interpretation ideas, fauna management advice, marketing and planning.

Join us on the 3rd of February to learn more. Take a walk up our virtual ‘garden path’ showcasing plans for a series of gardens representing New Zealand’s wetland types, and talk to the designers about plans for the visitor building and exhibits. Afterwards, you can join guided walks, take an art or photography class, watch arborists scale giant kahikatea, or join the kids in a range of artistic pursuits.


Shonagh Lindsay is a Trustee and the newsletter editor of the National Wetland Trust.

The state of Canterbury’s coastal wetland vegetation Waiology Jan 29

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By Philip Grove

Canterbury has a wide variety of wetland types in a range of landscapes from the mountains and high country through to the foothills, plains and the coast. The biological productivity of coastal wetlands and their ecological importance in the life cycles of many native fish and birds is well recognised. A national database of inland freshwater wetlands has been developed recently, but it does not cover saltmarsh or brackish wetland habitats, and is of limited accuracy in areas where freshwater wetlands adjoin or grade into brackish coastal lagoons and estuaries.

A small coastal wetland at Raupo Bay, Banks Peninsula, that is intermittently open to the sea also supports saltmarsh vegetation – three-square (Schoenoplectus pungens), sea rush (Junkus kraussii) and saltmarsh ribbonwood (Plagianthus divaricatus).

To complement the freshwater wetland database for Canterbury, Regional Council staff surveyed and mapped the vegetation of coastal wetlands over the period 2004-2011. The survey area included wetlands associated with estuaries, dunes, coastal lagoons and river mouths – that is wetland forms that are related directly or indirectly to coastal processes. Results of the survey were entered into a database recording type and extent of vegetated coastal wetland habitats following a standard wetland classification system.

The database contains information on 50 vegetated coastal wetlands in Canterbury Region, from the Tirohanga River mouth in the north to the Waitaki River mouth. The largest contiguous area of wetland vegetation in the database, more than 4000 ha, is located around the margins of Te Waihora/Lake Ellesmere.
Estuarine habitats supporting saltmarsh or brackish wetland vegetation comprised the majority of the mapped area – 4602 ha. However, only 341 ha of saltmarsh vegetation was recorded from within true estuaries subject to sea-water intrusion in daily tidal cycles. The greater part of Canterbury’s vegetated saltmarsh habitats are instead associated with brackish coastal lagoons that are not permanently open to the sea but are still affected to some degree by salt water.

Tidal estuary saltmarsh vegetation on mudflats at the southern end of Brooklands Lagoon. Three-square (Schoenoplectus pungens) and oioi (Apodasmia similis).

Freshwater wetland vegetation and habitats formed a smaller but significant proportion of the coastal wetlands surveyed; some 1140 ha or about 20% of the total wetland area. Freshwater wetlands were commonly present on or adjoining the inland margins of estuaries and brackish coastal lagoons, as well as along the edges of freshwater coastal lagoons and river mouth lagoons (hāpua).

Native plant species remain the dominant element in the vegetation cover for the majority of the region’s saltmarsh habitats. The most abundant native vegetation types are saltmarsh herbfield, marsh ribbonwood (Plagianthus divaricatus) shrubland and sea rush (Juncus krausii ssp. australiensis) rushland. However, most of the freshwater wetland habitats within the coastal survey area were dominated by introduced plants, particularly willows and grasses, although native rushes and raupō are also common.

Prior to European settlement, large freshwater wetlands occupied the low plains connecting the region’s coastal lagoons, estuaries and hāpua. For the most part these links no longer exist. Drainage of this low-lying land for agricultural and urban development has reduced the formerly extensive complex of freshwater and estuarine wetlands to the isolated fragments that remain around river mouths, estuaries and coastal lagoons. Human-induced loss of saltmarsh and other coastal wetland vegetation in the region is on-going. There have however also been examples of successful restoration of some coastal wetland habitats over the last decade, such as at Charlesworth Reserve on the Avon-Heathcote Estuary and Otipua Wetland near Timaru. The importance of Te Waihora/Lake Ellesmere margins, which support more than 80% of the region’s remaining saltmarsh habitats, has been recognised with the inclusion of vegetation values in the National Water Conservation Amendment Order of 2011.

Following the Canterbury earthquakes of September 2010 and February 2011, significant changes have been recorded in bed level and hydrology in and around the Avon-Heathcote Estuary and Brooklands Lagoon. Repeating the vegetation survey and mapping of these estuaries in a few years when plant distributions have adjusted to the new conditions will help provide a measurable record of changes to extent and type of wetland habitats.


Philip Grove is a terrestrial and wetland ecologist at Canterbury Regional Council.

From “swamps” to “wetlands”: The transformation of wetlands as both conceptual and physical landscapes Waiology Jan 28

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By Catherine Knight

The boardwalk through the wetland at Papaitonga, south of Levin, Horowhenua (photo: C. Knight).

Through time, not only has our environment been transformed, but also the way we perceive it and the words we use to describe it. No example illustrates this better than the “swamp” to “wetland” transformation. When European settlement of New Zealand began in earnest about 150 years ago, about 670, 000 hectares of freshwater wetlands existed. By the 20th century, this had been reduced to 100,000 hectares. Wetlands were seen as swamps – or, as Charles Hursthouse put it in 1857: “Damp and dripping forests, exhaling pestilent vapours from rank and rotten vegetation…” Not only were swamps “unproductive”, they were also undesirable to the European aesthetic – “messy” and without order. In order to transform these swamps into productive and useful land, they first had to be drained. Throughout the 19th century, settlers had drained smaller areas of swampland for their own farms and homes. But in the early 20th century, the government set about massive scale drainage works throughout the country, starting with Hauraki Plains, and Rangitaiki Swamp in the Bay of Plenty, to convert these areas into farmland and settlements.

In 1889, William Pember Reeves gave this poignant description of swamp environments and their desiccation:

Small streams ran out of the swamp… and disappeared in the shingle of the beach. When not disturbed with draining work, their water was sweet and clear. The swamps had been covered with tall flax, toetoe, rushes and small bushes, green and beautiful in the sunlight, but as drains did their work, the peat sank, cracked and dried, the surface was systematically burnt and became stretches of black, hideous ashes and mud, poached up by the hoofs of cattle.

Today, New Zealand has the unenviable record of an 85 to 90 per cent reduction in wetlands since European settlement. As Geoff Park states in Environmental Histories of New Zealand, one of the most dramatic declines anywhere in the world. But with that dramatic decline has come a heightening in awareness of the ecological importance of wetlands. No longer dismissed as useless “swamps”, wetlands are recognised as having numerous functions vital to both environmental and human wellbeing. Acting rather like a giant sponge, they control water flow and quality. Plants slow the flow of surface water from the land, absorbing excess water during flood events. During dry periods, stored water is slowly released from wetlands, maintaining flows. Bacteria in the damp soils of wetlands absorb and break down 90 per cent of the nitrogen contained in farm run-off (such as in fertilisers and animal waste). Plants also trap waterborne sediment, preventing silt entering streams and harbours. They are highly productive ecosystems, providing habitat and a rich food source for fish, birds and other animals. They absorb large amounts of water and nutrients from outside sources and contain micro-organisms (fungi and bacteria) that efficiently decompose and recycle nutrients.

In the Manawatu, which is the focus of my current research, much of the flood plains of the lower Manawatu River were once a network of wetlands of some nature: swamps, lagoons created by the cut-off meanders of the river, and once the river reached the Tasman Sea, an extensive estuary. These wetlands were greatly valued (and contested) by Maori in the region, who treated them as a highly valued resource, particularly as eel fisheries. However, to the European, they were seen as a barrier to the productive use of land, as well as an unwelcome encumbrance to movement across the land. Drainage boards were established almost immediately to create and maintain drains across the swampiest of land, thereby allowing the “march of progress” to proceed, in the form of the ever-expanding pastoral landscape. One of the largest wetlands to be drained was Taonui Swamp, in the basin between Oroua and Manawatu Rivers. Others that were initially valued as flax-producing swamps, but later drained when the boom was over, were the Makerua and Moutoa Swamps.

Palmerston North itself was established on an area that included five lagoons, all highly valued by Maori, whose settlements were sited close by. All but one of these is now drained. Even the lagoon that remains is in a form vastly transformed from its indigenous state, and few Palmerstonians are aware of its illustrious pre-European history.

Awapuni Lagoon in 1881. It was highly valued by the Rangitane people who had a settlement at Awapuni, and was initially valued as a place of recreation by early settlers of Palmerston North, but was later drained. Source: Palmerston North City Library, Digitisation ID no.: 2007N_Awa1_EPN_0252.

Sadly, no amount of effort will restore the likes of the Awapuni Lagoon, once located on the western boundary of the city, which can now only be remembered by historical photographs (see above). But, like many other regions of New Zealand, wetlands are undergoing a revival in the Manawatu, both in terms of the value attributed to them, and the effort invested in restoring them.

One such example is the Manawatu Estuary. In 2005, after prolonged representations by the self-appointed guardians of the estuary, the Manawatu Estuary Trust, the Manawatu Estuary was designated as New Zealand’s sixth Wetland of International Importance, under the RAMSAR convention, an inter-government treaty on the conservation of wetlands. It is now recognised that the estuary has one of the most diverse ranges of birds to be seen at any one place in New Zealand, a total of 93 species have been identified at the estuary. It is a significant area of salt marsh and mudflat and an important feeding ground for many birds, including the migratory eastern bar-tailed godwit, which flies non-stop for 11, 000 kms from Siberia to escape the harsh northern winter. The estuary is also a permanent home to 13 species of birds, six species of fish and four plants species, all of which are threatened. It regularly supports about one per cent of the world population of wrybills.

Ashhurst wetland, near the Ashhurst Domain (photo: C. Knight).

Another wetland that has been the focus of local restoration efforts is Ashhurst wetland (pictured). And while an investigation of the site’s environmental history reveals that this is not a “restoration” in the strict sense, the restoration project has nevertheless produced an ecosystem of significant natural value and a landscape of aesthetic value, from which many derive considerable pleasure. Hopefully, restoration projects of the future will also reveal the important ecological, aesthetic, recreational and cultural values of places once dismissed as “unproductive wastelands”.


Dr Catherine Knight is an environmental history researcher, and an honorary research associate at Massey University. She is currently working on a book exploring the environmental history of the Manawatu region, from prehistory to today.

This article adapted from a post originally published on envirohistory NZ on 6 December 2009.

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