Application of the Relative Risk Model (RRM) to Investigate Multiple Risks to the Miranda Ramsar site.

This report presents the application of the Relative Risk Model (RRM) to investigate multiple risks to the ecology of the Ramsar site in the southern Firth of Thames. The application of this model is part of the multi-agency collaborative 'Muddy Feet Phase II: the Firth of Thames Ramsar site' project, which is co-ordinated by Environment Waikato and Franklin, Hauraki and Thames Coromandel District Councils. The primary objective of the application of the RRM to the Ramsar site is to assess the relative threat posed by different risk sources, and their stressors, to selected ecological values of the Ramsar site and surrounds.

The Relative Risk Model (RRM) is an analytical tool, which can be used to help decision-making. The process adopted by the Muddy Feet Phase II project was to use the RRM as a framework for a series of workshops discussing potential risks to the Firth of Thames Ramsar site. All known information was integrated into the RRM, which was used to predict the risks to the Ramsar site from various stressors and sources. The RRM can utilise both precise information and estimates to rank the likely effects of different activities or stressors (e.g. nutrient runoff from agricultural land use) on various parts of the environments (e.g. intertidal or subtidal areas). Thus, all information available can be integrated into the model, and the model output provides an overview of the relative importance of different risks to the values (e.g. birds, fish and vegetation) identified by stakeholders. This makes the model a potentially valuable and cost-effective tool to facilitate the decision-making processes by management agencies. In particular, it provides an initial low effort overview of relative sources of stress on the environment which can be used to focus later efforts, through direct management actions and/or determining where more information is required. Collaborators on the project include the four principal District Councils of the catchment draining into the southern Firth of Thames (Franklin, Hauraki, Matamata Piako and Thames Coromandel District Councils); Environment Waikato and Auckland Regional Council; the Department of Conservation and the Ministry of Fisheries. Representatives from these agencies participated in workshops where ecological values of the Ramsar site and surrounds were identified, as were stressors and sources of stressors that may threaten the site. A workshop was also held for members of the community, where values of the Ramsar site and perceived threats to these were recorded. Iwi values were incorporated through an analysis of submissions to Environment Waikato policy over the last six years, and feedback on these was sought in a hui. These discussions were essential for the RRM-building process. Following the identification of agencies and community values and concerns, the RRM was constructed around those values and concerns. The RRM structure consists of three components: 1. Sources: represent activities (e.g. sewage discharge, agriculture practices) that produce risks through one or many stressor(s) (e.g. chemical contaminants, sedimentation, habitat loss), referred to in this study as Sources of Stressors. 2. Habitat: represents the areas or sections within the region where the ecological values (e.g. species of birds and fish) live and which they use, referred to here as Habitats. 3. Ecological Impact: represents the impact on the management goals such as ecological, biological or other environmental values that we want to protect (e.g. the continued survival and well-being of various species of plants and animals, as well as water and air quality). These management goals are denoted Assessment Endpoints here. The RRM provides a characterisation of the problem (indication of the relative importance of the risks identified), not specific answers (which may be, indirectly, in the form of recommendations for management responses which could reduce risks). However, the ranking of risks in terms of importance provides essential information which will help decision-making. Further, the use of the RRM as a framework provides a process which allows participants to communicate about, and agree on, management goals and threats to these, based on all available information. As more information becomes available, the RRM can be made more accurate and uncertainties reduced. This process can be documented and made available to interest groups, other agencies and the public. Overall the RRM results indicated that the region is already under pressure from a number of existing sources of stressors, particularly agricultural land use. Where limited information was available, or uncertainty about impacts of some sources in an area was high (e. g. for urban and industrial land use, marine farms, mangrove expansion, and climate change), two different scenarios were modelled. These scenarios represent predicted risk based on best present day knowledge and worst case scenario, respectively. Predicted risk represents the likely predicted risk based on best knowledge available, and worst case risk represents worst case risks where some sources are given relatively high scores (due to the possibility that (a) they could increase and have major ecosystem impacts in the near future; or (b) the current risk may be underestimated due to limited knowledge). The predictions of the RRM for the Ramsar site and its catchment found that: • The greatest stressor on the biological endpoints appears to be from terrestrial drivers, including the generation and delivery of sediments, contaminants, habitat loss, invasive species and nutrients. Agricultural land use (dairy farming) contributed by far the largest risk to the Ramsar site. Climate change, Firth of Thames sediments, point sources, fishing, urban and industrial land use, and mangrove expansion posed lesser but important risks. • In the worst case scenario, the risk posed by climate change was similar to that of agriculture land use, both by far exceeding risks posed by other sources. • In both scenarios, the relative risks from all other sources were quite low. • Sedimentation was found to be the biggest stressor, and the largest sources of sediments were agricultural land use and sediments already in the Firth of Thames. • The greatest habitat risk was to the tidal flats of the Ramsar site. • Lower, but relatively important risks existed for the water column, the sub-tidal seabed, and stilt ponds. • Mangroves and open coastal areas were shown to be at relatively low risk, and the relative risk to the airspace used by birds was very low. • At highest risk among the biological values were shellfish beds, some fish species and marine worms. • The second highest risk was found to be to some shorebirds, the area important for creating the Chenier bank, saltmarsh, and other fish species. • Whitebait (inanga and smelt) and water quality were at medium risk, and vegetation only marginally exposed to salt water influences (bachelor's button, sedges, Maori musk, burmedic short grassland, and ryegrass), and the coastal birds (shags, heron and banded rail) and mud crabs were at the lowest risk. The high risk score predicted from agricultural land use is not surprising considering the extensive dairy farming that dominates the catchment. In particular, the terrestrial sediment loads and their accumulation in the coastal marine environments of the Firth of Thames contribute the major environmental risk to the Ramsar site. Whilst sediment supply rates from land are thought to be relatively low at present, the sediment reservoir in the Firth (built up from decades of high sedimentation rates from the catchment) is thought to be fuelling the recent dramatic expansion of the mangrove forests. These large-scale effects and changes demonstrate the potential for terrestrial inputs to significantly alter the coastal environment, and highlight the fact that even if sediment runoff from land is reduced, trends of increasing sedimentation could continue to occur for a while because of the storage of sediments in the Firth. The highest loads of sediments, contaminants and nutrients are often associated with seasonal or periodic flood events. The frequency of these flood events may change with global climate change effects, which is why the worst case scenario predicted that climate change can also be a large contributor of risk to the region. Overall the application of the RRM to the Ramsar site was useful. The work confirmed that the RRM is a rapid, powerful, flexible and cost effective tool that can provide an overview of the relative risks to a site from multiple sources, generating outputs that resource managers can likely use to aid decision-making. The overall scope of this study was to establish the RRM as a tool for the Ramsar site management. This tool can be used, and expanded upon, by management agencies and other stakeholders. The model used a number of stressors and environmental values that are likely to be representative of most stakeholder concerns, but these can be modified easily with new input. As such, the RRM results presented here are considered a starting point for discussion and a guide to prioritise management actions. The largest uncertainty source found in this risk assessment was the lack of data or scientific knowledge and understanding. As future studies fill these data and information gaps, uncertainty will be reduced. Based on our review of the available information for the site as well as the Monte Carlo uncertainty analysis, we created a list of the most pressing information needs that we think would aid in the development of future studies to help reduce the uncertainty and above all aid in the sustainable management of the Ramsar site. They are: • Data for climate change, particularly the combined effects of predicted sea level rise and subsidence in the Firth of Thames, and an assessment of the effects of sea level rise on the extent of the habitats considered in this report. • Sediment budget for the Firth of Thames, quantifying annual sediment loads from the land, and the size of the sediment reservoir stored in the Firth basin. • Estimate of the size of roosting and feeding habitat available to shorebirds; investigations determining whether mangrove expansion reduces the size of habitat available for shorebirds or whether the intertidal area seaward of the mangroves is building up at rates similar to the expansion of mangroves. • Further investigations determining the sources and likely effects of the elevated mercury concentrations found in sediments at the mouth of the Piako River. • Quantification of nutrient concentrations in water and sediments of the Ramsar site, a quantification of the major sources of nutrients, and assessment of any likely effects of nutrient enrichment on the components of the Ramsar site. • Phytoplankton or algal growth limitation at the Ramsar site. • Effects in the wider Firth from nutrient and sediment discharges. • Quantification of the biosecurity risks to the Ramsar site from the marine farming at Wilson Bay. • Quantification of the biosecurity and other risks to the Ramsar site from terrestrial invasive species, such as rodents, mustelids and cats. Following on from the risk assessment described in this report, the Muddy Feet Phase II project proceeded to identify priority actions to reduce key risks to the Ramsar site. This was achieved through identifying what can be done to minimise each of the risks included in the model, and who should do it, and comparing this to what management agencies are currently doing or have plans to do in the near future. Actions not covered by existing work programmes were prioritised, as were any information needs identified, and recommendations provided to all agencies involved. The results from this part of the project are reported in Brownell (in press).

Firth of Thames RAMSAR site.

Workshops undertaken in 2005 and 2006

Varied

See report

Data reported in Environment Waikato Technical report. Report available in .pdf format from Environment Waikato's website www.ew.govt.nz/publications.

Management and protection of Miranda Ramsar site.

Report freely available from Environment Waikato library or website. Sensitivity/Confidentiality: No confidentiality.

Study complete.

Related information: Bayesian network model study.