Otago's wetlands are some of the most valuable ecosystems in the region, and to recognise and protect their ecological, cultural, and socio-economic values.

170 Regionally Significant Wetlands and Wetland Management Areas were identified and included in schedule 9 of Regional Plan – Water for Otago.

The recently revised and operative National Policy Statement for Freshwater Management (NPS-FM 2020) requires regional councils to implement more stringent regulations for the protection and management of natural wetlands extent and values. The new requirements do not align completely with the ORC criteria previously used for wetland provisions as previously mapping was undertaken to identify and determine significant wetland values according to a range of ecological significance criteria and utilised a more limited range of tools and aerial imagery with which the wetland boundaries were mapped.

Otago's wetlands are some of the most valuable ecosystems in the region, and to recognise and protect their ecological, cultural, and socio-economic values 170 Regionally Significant Wetlands and Wetland Management Areas were identified and included in schedule 9 of Regional Plan – Water for Otago.

The recently revised and operative National Policy Statement for Freshwater Management (NPS-FM 2020) requires regional councils to implement more stringent regulations for the protection and management of natural wetlands extent and values. The new requirements do not align completely with the ORC criteria previously used for wetland provisions as previously mapping was undertaken to identify and determine significant wetland values according to a range of ecological significance criteria and utilised a more limited range of tools and aerial imagery with which the wetland boundaries were mapped.

Following the new national guidelines a detailed and comprehensive regional wetland mapping programme was devised including wetland risk and prioritisation frameworks. The programme consisted of mapping wetlands in three phases.

In phase I & II, which stretched over two years (FY 2021-22 & 2022-2023), natural wetlands in the Upper Taieri Scroll Plains and Regionally Significant Wetlands/Wetland Management Areas were re-defined and their boundaries revised. A relatively small number of RSWs were left with unchanged boundaries.

The more accurately determined RSWs mapped a total area of 12,239 hectares. Overall, this represents a reduction of 927 hectares in extent compared to the original mapping (RP-W Schedule 9 maps), as some originally mapped wetland complexes included significant areas of terrestrial habitat. In addition, one originally mapped wetland was assessed as entirely terrestrial habitat and removed from the revised layer.

Swamps and marshes made up the greatest extent of the re-delineated wetlands, and most wetlands were assessed as of indigenous or mixed status. Ground truthing of 16 of the regionally significant wetlands resulted in some wetlands increasing in size, some changing very little, and some decreasing, with an overall reduction in size of six hectares.

In Upper Taieri Scroll Plains Wetland Complex alone 4,681.5 hectares of wetlands were identified totalling 11,450 wetland polygons (see Image 1). The methodologies employed (calculating wetness indices, depression analyses and manual digitisation) mapped potential wetlands and most likely to meet the RMA definition of ‘wetland’, but ground truthing would be required to confirm whether these wetlands meet the ‘natural wetland’ definition criteria as per the NPS-FM (2020) (a detailed report is available on ORC website).

To assess, how many of the RMA defined wetlands meet the NPS-FM (2020) wetland criteria, a subset of 151 wetlands across the Taieri Scroll Plains were tested and the results suggest that 60% of the surveyed wetlands do meet the criteria (as per Wetland Delineation Protocols; Vegetation Test) and qualify as wetlands, while 40% do not qualify or require further investigation (such as Wetland Delineation; Hydrology and Hydric Soil Tests).

Due to the inherent complexity of the system an alternative management approach was proposed for managing values in the Upper Taieri Scroll Plains where three management zones will be delineated as opposed to individual wetland polygons. Each of the management zone will be defined in relation to its pertinent values such as the Taieri Rive and riparian areas, tributaries, natural wetlands, flood plains and scroll plains (work in progress).

Phase III of the programme is to map all natural wetlands in the region that are larger than 500 m2 and smaller if ephemeral wetland and/or known to contain threatened species. This represents a significant body of work and may take several years to complete, as Otago contains large areas of dissected hill country and upland landforms, that will contain tens of thousands of smaller and ephemeral wetlands.

Therefore, a prioritisation framework (wetlands at risk) was utilised that helped selecting freshwater management units to be mapped first. Under phase III mapping in Dunedin & Coast, North Otago and Catlins FMUs and Upper Lakes Rohe has been completed in FYs 2022-2023 and 2023-2024.

The data suggests that there are 17 RSWs and 5,389 Natural Wetlands in Upper Lakes, 13 RSWs and 5,686 Natural Wetlands in North Otago, 22 RSWs and 2, 431 Natural Wetlands in Dunedin & Coast and 21 RSWs and 1,799 Natural Wetlands in Catlins (for more details about the wetland types, area and location please contact Sami.Khan@orc.govt.nz).

Also, partial mapping has been completed in Manuherekia and Lower Clutha rohe and will be fully accomplished before end of the current fiscal year (2024-2025). Wetland mapping in remainder of the region (i.e., Taieri FMU, Roxburgh and Dunstan Rohe) are aimed to be completed in the next FY (2025-2026).

All the wetland spatial data (maps, extent and values) will be compiled as an Interactive Regional Wetland Inventory (GIS infrastructure) containing the following about each mapped wetland.

1. 1. unique identifier (code) and location,
   2. GIS polygon (boundary),
   3. classification of wetland type as per Johnson and Gerbeaux Wetland Classification System (2004),
   4. wetland values (exotic, native, etc.), and
   5. wetland condition (values and ecosystem health monitoring information)

Once the inventory is ready and notified, landowners will be contacted and informed about the existence of wetlands in their properties and if any dispute arises regarding the existence or extent of a wetland, will be resolved using the Ministry for the Environment’s developed Wetland Delineation Tools. Unlike the Schedule 9 of the current regional plan maps, it is recommended that the Inventory be treated as a live resource.

The draft Otago Land and Water Regional Plan (dLWRP) details policies, guidelines, regulations and standards that must be actioned such as NPS-FM (2020), Resource Management Stock Exclusion regulations (2020) and Resource Management National Environmental Standards for Freshwater (2020). These guidelines and regulations set the standards for natural wetlands management and monitoring.

To meet the requirements, in 2022, a project was initiated with Manaaki Whenua Landcare Research (MWLR) to better understand the ecology of the Upper Taieri Scroll Plain Wetland Complex to help informing an adequate management and monitoring plan. The work included assessing vegetation and soil condition in 151 plots across the scroll plain.

Results revealed presence of 52 native plant species, seven of which are classified as threatened. Results depicted heavily modified nature of the landscape where 30% of the sites contained exclusively exotic species and 32% had 50% or more cover of exotic non-wetland species, and the only woody species recorded were two species of willow (both invasive exotics).

Nearly 2% of the sites contained solely native species, and all these plots had standing water present at time of monitoring (during a drought) and only 7% of the plots had greater than 50% cover of native species. Recent grazing was evident in all sampling locations of the wetlands despite some areas were classified as non-grazing zones (retired permanently) while current grazing was noted in more than half of the sites.

The soil chemistry varied with scroll plain locations, and to some degree with grazing. Both soil pH and conductivity (EC) increased with distance down catchment. Soils in the Paerau basin tended to have higher percentages of nitrogen, potassium, and phosphorus than soils in the Māniatoto basin and Tunaheketaka (See report and publications to read report).

In 2023-2024 the monitoring network was extended by adding four more Regionally Significant Wetlands i.e., Tahakopa River Bogs, Lake Tuakitoto Wetlands, Upper Black Swamp Marshes and Fortification Creek Wetland Management Area.

Forty-four plots were established across four wetlands, with an average of one plot per 20 ha. A total of 48 plant species were recorded in Tahakopa Marshes, eight of which were exotic and one threatened species. In Tuakitoto, 31 plant species were recorded and 18 of which were exotic. In Upper Black Stream Marshes, there were total of 38 plants species, 10 of which were exotic.

In Fortification Creek Wetland Complex, a total of 84 plant species were recorded, eight of which were threatened and 19 exotic species. A total of 20 bird species were documented across the four wetland sites and only two of which were threatened species (report will be uploaded to the ORC website as the webpage is under construction).

With over 15,000 wetland sites (and counting), representing 15 (total 22 nationally) vegetation types of wetlands spread across nine Freshwater Management Units/Rohe, there was a dire need of a framework that would enable council to regularly monitor and report on extent, state and condition trends of a subset, representative of the diversity of wetland types found in the region at the level of the FMU.

A regional framework³ was developed that helped selecting of a subset for monitoring considering relative number of regionally significant wetlands, distribution and frequency of threatened species, range of indigenous biodiversity, key threats to sustaining and enhancing wetlands and finally, the resources available to maintain the monitoring and reporting system.

A total of 300 - 400 representative wetland sites across the region were shortlisted to be sampled using a restricted randomised approach on a ten-yearly rotation. Approximately half of these sites represent wetlands of regional significance (RSWs) and half are sites randomly selected using restricted randomisation basis to cover wetland types, within FMU/Rohe and elevation bands.

Each year, 40 wetlands will be sampled across the spectrum of FMUs, wetland types, and habitat features, with an emphasis on lowland (60%) and montane (30%) sites reflecting threat levels. This approach will enable the council to report on the state and condition of wetlands in the region as directed in the NPS-FM (2020).

A second framework was developed suggesting methods for monitoring wetland condition in Otago as directed in the NPS-FM (2020). Firstly, an operational definition of wetland health and condition was developed, considering the major Otago Regional Council policies related to wetlands, and detail metrics and approaches for assessing wetland condition.

Monitoring methods include wetland condition and extent metrics that are clearly linked to facilitate a common understanding of monitoring rationale, and to focus attention on where improvements may be needed in the future.

Otago region supports the most diverse and numerous wetland types of any region in New Zealand, and monitoring condition and extent therefore require a suite of methods at different scales to adequately report on progress towards maintaining and enhancing their health.

Experts suggested that a relevant and effective monitoring system focuses on the both the values identified for protection and the major threats to these in the area. Monitoring threats is relevant because it guides the formulations of policies and regulations.

For biodiversity in general, monitoring can be challenging because of the numerous components, diverse values, multiple threats, and the natural dynamics of most ecosystems. However, the NPS-FM 2020 sets out the values of interest regarding wetlands and provides a clear context for developing a wetland condition and extent monitoring framework.

Our experts further viewed that enhanced wetland condition means increasing dominance of native species, including birds, plants, fish and invertebrates, and reduced threats from plant and animal pests, and encroaching landuse that reduces water quality and quantity in the wetland.

Therefore, Otago’s newly developed framework outlines a combination of inhouse and field measurements along with the appropriateness of the indicators for condition or pressure measures. The methods outlined in the framework are not based on explicit scoring system, as per Clarkson et al. (2013)4 rather suggest a three-category score, to decrease observer variance and ambiguity.

The newly developed monitoring methods were trialled on selected wetlands in Catlins FMU with the relevant information to assess their utility and develop a reporting format at the management unit level (field work partially completed and report is being prepared).

³ Report will soon be uploaded to the website as the webpage is currently being developed.