Part three: Responding to the effects of climate change
This part covers:
- integrating climate change into council decision-making
- qualitatively assessing the influence of climate change on council functions and services
- undertaking preliminary assessments for the impacts of climate change
- considering heavy rainfall in assessing the effects of climate change
- using a full risk assessment process for climate change effects
- assessing climate change effects using complex scenarios.
Integrating climate change into council decision-making
Climate change is relevant to a wide range of local government functions. It adds to the many uncertainties that councils must consider in all their planning, risk assessment and decision-making. Every council function or service that relies on, or is affected by, climate parameters such as rainfall, sea level or temperature, can be affected by climate change.
Climate change considerations are unlikely to drive or initiate local government action on their own. Rather, through the application of risk management processes in assessing and prioritising possible responses to the effects of climate change, they may modify an outcome. Many councils have already taken steps towards integrating climate change in plans.
The emphasis in this part of the guide is on:
- understanding the scope and variation of climate change
- deciding on priorities for action
- applying risk assessment as a method to determine adaptation responses based on the level of risk.
Climate change risk assessment is best undertaken as part of ongoing council activities, not as a separate issue. It is not necessary to address the impacts of climate change on all functions and services at once. It is a matter of prioritising.
Generally, councils can use a series of steps of increasing complexity to assess whether climate change is relevant to a particular council function, how significant its impact might be, and what the appropriate response might be.
Assessing the influence of climate change on council functions and services has three key stages:
- The first stage is to qualitatively identify whether a specific council function or service could be affected by climate change or, more generally, which council functions are vulnerable to climate variability and, therefore, to climate change.
- If this process identifies a possible climate change effect, a preliminary assessment should be undertaken. This consists of using a range of scenarios for climate change and other drivers to test the likely significance of climate change; and to see whether existing planning and management provisions have a sufficient safety margin to cover any resulting change in risk or resource availability.
- If it appears that existing provisions do not adequately cover the future change in risk, a more detailed scientific and technical risk assessment should be undertaken; this would be followed by an analysis of response options to manage the risk over appropriate timeframes.
While the more detailed risk assessment refers only to the risks associated with climate change, these risks are best assessed together with risks from other hazards and climate variability where possible and not in isolation. The process outlined is not the only one that can be used. If a local authority has an existing risk assessment process, climate change should simply be added in.
The long-term nature of climate change means that the lifetime of a development, service or infrastructure must be considered when assessing risk. The risk may not exist now, but may evolve as a result of climate change. This risk assessment, therefore, recognises the time evolution of risks by introducing a planning horizon and considering the risk at various steps along the way. For a lifetime of 100 years the risk may be evaluated as it is now and as it will be in 25, 50, 75, and 100 years, giving options for responses over time.
There is a complex relationship between coastal hazards and climate change, therefore a detailed risk assessment using independent expertise is usually required when considering activities in coastal areas. A simple screening assessment is not generally appropriate for such a task. For further detail, see the source report Climate Change Effects and Impacts Assessment and Coastal Hazards and Climate Change (available at www.mfe.govt.nz/publications/climate/climate-change-effect-impacts-assessments-may08/index.html and www.mfe.govt.nz/publications/climate/coastal-hazards-climate-change-guidance-manual respectively.)
Stage One: Qualitative assessment of the influence of climate change
Table 4 and Table 5 overleaf are designed to help council staff understand and qualitatively determine the role of climate, and hence climate change, for a wide range of council functions and services.
Table 4 lists specific council functions, assets and activities and how they could be affected by climate change. Table 5 summarises natural resources that are managed by councils and their sensitivity to climate and climate change.
In using these tables, remember that they are not an exhaustive source of information on the impacts of climate change on all council functions and services. Climate change and its effects should be considered relative to other changes: it will not occur independently of natural climate variability or of future social and economic changes. This guide does not provide guidance on how to make projections of future socio-economic changes – councils will generally have their own resources to estimate future population change and development projections, and the infrastructure requirements to accommodate these.
Table 4: Local government functions and possible climate change outcomes
| Function | Affected assets or activities | Key climate influences | Possible effects | Section in Table 4.2 of the source report giving type / explanation of effects |
|---|---|---|---|---|
| Water supply and irrigation | Infrastructure | Reduced rainfall, extreme rainfall events, and increased temperature | Reduced security of supply (depending on water source) Contamination of water supply |
See Rivers, Groundwater, Water quality, Water availability, Coastal areas. (Note that there are also rainfall effects in areas dependent on rain water.) |
| Wastewater | Infrastructure | Increased rainfall | More intense rainfall (extreme events) will cause more inflow and infiltration into the wastewater network Wet weather overflow events will increase in frequency and volume Longer dry spells will increase the likelihood of blockages and related dry-weather overflows |
See Drainage |
| Stormwater | Reticulation Stopbanks |
Increased rainfall Sea-level rise |
Increased frequency and/or volume of system flooding Increased peak flows in streams and related erosion Groundwater level changes Saltwater intrusion in coastal zones Changing flood plains and greater likelihood of damage to properties and infrastructure |
See Rivers, Drainage, Coastal areas |
| Roading | Road network and associated infrastructure (power, telecommunications, drainage) | Extreme rainfall events, extreme winds, high temperatures | Disruption due to flooding, landslides, fallen trees and lines Direct effects of wind exposure on heavy vehicles |
See Drainage, Natural hazards |
| Urban land use planning / policy development | Management of development in the private sector Expansion of urban areas Infrastructure and communications planning |
All | Inappropriate location of urban expansion areas Inadequate or inappropriate infrastructure, costly retrofitting of systems |
See particularly Rivers, Groundwater, Drainage, Coastal areas, Natural hazards |
| Land management | Rural land management | Changes in rainfall, wind, and temperature | Enhanced erosion Changes in type / distribution of pest species Increased fire risk Reduction in water availability for irrigation Changes in appropriate land use |
See Water availability, Erosion, Biodiversity, Biosecurity, Natural hazards |
| Water management | Management of watercourses / lakes / wetlands | Changes in rainfall and temperature | More variation in water volumes possible Reduced water quality Sedimentation and weed growth Changes in type / distribution of pest species |
See Rivers, Lakes, Wetlands, Water quality, Drainage, Erosion, Biosecurity |
| Coastal management | Infrastructure Management of coastal development |
Temperature changes leading to sea-level changes Extreme storm events |
Coastal erosion and flooding Disruption in roading, communications Loss of private property and community assets Effects on water quality |
See Coastal areas, Natural hazards |
| Civil defence and emergency management | Emergency planning and response, and recovery operations | Extreme events | Greater risks to public safety, and resources needed to manage flood, rural fire, landslip and storm events | See Natural hazards |
| Biosecurity | Pest management | Temperature and rainfall changes | Changes in range of pest species | See Biosecurity, Biodiversity |
| Open space and community facilities management | Planning and management of parks, playing fields and urban open spaces | Temperature and rainfall changes Extreme wind and rainfall events |
Changes / reduction in water availability Changes in biodiversity Changes in type / distribution of pest species Groundwater change Saltwater intrusion in coastal zones Need for more shelter in urban spaces |
See Groundwater, Drainage, Water availability, Biodiversity, Coastal areas |
| Transport | Management of public transport Provision of footpaths, cycleways, etc |
Changes in temperatures, wind and rainfall | Changed maintenance needs for public transport (road, rail) infrastructure Disruption due to extreme events |
See Drainage, Natural hazards |
| Waste management | Transfer stations and landfills | Changes in rainfall and temperature | Increased surface flooding risk Biosecurity changes Changes in ground water level and leaching |
See Biosecurity, Natural hazards |
| Energy | Transmission lines | Extreme wind, high temperatures | Outages from damaged lines | See Natural hazards |
Table 5: Sensitivity of natural resources to present climate and climate change
| Natural resource | Key climate influence | Impacts of climate change | Present sensitivity to climate |
|---|---|---|---|
| Rivers | Rainfall | River flows likely to, on average, increase in the west and decrease in the east of New Zealand More intense precipitation events would increase flooding (by 2070 this could be from no change, up to a fourfold increase in the frequency of heavy rainfall events) Less water for irrigation in northern and eastern areas Increased problems with water quality |
Strong seasonal, interannual and interdecadal fluctuations (see the example in Box 4.1 at the end of section 4.4 of the source report, on peak flows in Bay of Plenty) |
| Lakes | Temperature and rainfall | Lake levels likely to increase, on average, in western and central parts of New Zealand, and possibly to decrease in some eastern areas Higher temperatures and changes in rainfall, particularly in areas such as the Rotorua Lakes, could result in a range of effects, including:
|
Seasonal and interannual fluctuations |
| Wetlands | Temperature, rainfall, sea-level rise | Coastal and inland wetlands would be adversely affected by temperature increases, rainfall increases or decreases and sea-level rise | Many already under threat |
| Groundwater | Rainfall | Little change to groundwater recharge is expected in eastern New Zealand, but increased demand for water is likely Some localised aquifers in northern and eastern regions could experience reduced recharge. For example, small coastal aquifers in Northland would be under threat from reduced rainfall |
Seasonal fluctuations; but at present, generally stable over the longer term |
| Water quality | Temperature and rainfall | Reduced rainfall and increased temperatures could have significant impacts on the quality of surface water resources in northern and eastern New Zealand Lower stream flows or lake levels would increase nutrient loading and lead to increased eutrophication |
Most sensitive during summer months and in drier years |
| Drainage | Rainfall | Increased frequency of intense rainfall events could occur throughout New Zealand, which would lead to increased surface flooding and stormwater flows, and increased frequency of groundwater level changes | Natural year-to-year variation in the location and size of heavy rainfall events |
| Water availability | Rainfall | Decreases in rainfall, which are most likely in the north and east of New Zealand, coupled with increased demand, would lead to decreased security of water supply | Dry summers, or extended droughts |
| Erosion | Rainfall and wind | Increased rainfall in the west, and more intense rainfall events throughout New Zealand, could lead to increased soil erosion, including landslides | Intense rainfall events can arise with subtropical lows, and localised low pressure cells |
| Natural resource | Key climate influence | Impacts of climate change | Present sensitivity to climate |
| Biodiversity | Temperature, rainfall, wind | Increased temperature, reduced rainfall and more frequent drying westerly winds (possible in the east) would lead to changes in distribution and composition of native forest ecosystems throughout New Zealand Fragmented native forests in the north and east of New Zealand will be most vulnerable An increased biosecurity risk, with invasive temperate and subtropical species, would also have negative impacts on native flora and fauna Small increases in temperature will significantly increase the incidence of pest outbreaks in New Zealand, particularly in the North Island and the north of the South Island Both existing and potential new plant and animal pests could become established more widely, even with a slight increase in temperature |
Drought can have a severe impact, eg, some native vegetation was adversely affected in Hawke’s Bay after the 1997/98 El Niño drought |
| Coastal areas | Sea-level rise, storm frequency and intensity, wave climate, sediment supply | Effects of sea-level rise and other changes will vary regionally and locally Coastal erosion is likely to be accelerated where it is already occurring and erosion may become a problem over time in coastal areas that are presently either stable or are advancing |
Short- and medium-term fluctuations in sea levels (ie, up to about 30 years) are dominated by ENSO and IPO variations |
| Air | Temperature, rainfall, wind | Increased temperatures in Auckland might increase photochemical smog Fewer cold nights may reduce particulate smog problems in winter in affected towns |
|
| Natural hazards | Temperature, rainfall, wind | The general indications are that New Zealand could experience more climatic extremes in the future. These could include:
|
There have been more frequent and intense El Niño events in recent decades, possibly associated with the Interdecadal Pacific Oscillation. The worldwide cost of extreme weather damage has increased owing to a mixture of climatic, economic and social factors |
Deciding on the need for quantitative assessment
Having qualitatively determined that climate change could affect a council function or service, a decision has to be made as to whether the impact warrants a quantitative analysis.
Quantitative assessment is most likely to be required:
- whenever infrastructure is upgraded anyway or major developments are undertaken
- if some infrastructure and developments have a lifetime of more than 30 years. Is their design consistent with climate predictions?
- whenever council plans come up for review. If the topic is dependent on, or affected by, climate and the plan regulates long-term actions, it may be affected by climate change.
The following principles are also important in deciding on quantitative assessment:
- Future generations need to be able to respond to risks caused by a changing climate. There is a need to avoid locking the community into a situation of increasing risk which has limited risk management options.
- The risk from climate change varies over time. Analysis and action on climate change should be deferred only if its effects are likely to be negligible compared to other pressures.
Other questions that could be asked include:
- Could an existing problem (eg, recurrent inundation) be exacerbated by climate change?
- What foreseeable problem may be caused or exacerbated by climate change?
- Is the issue complex (eg, deciding on the location of a new suburb as opposed to only one building)?
- Is the location sensitive to climate change (eg, on a flood plain as opposed to a bedrock hilltop)?
- Does a decision imply a permanent long-term change (eg, locating a new suburb as opposed to permitting a campsite)?
- Is much infrastructure involved and are services provided (eg, compare an urban area with a remote rural location)?
Developing quantitative scenarios of the likely effects of climate change
There is much uncertainty about the extent of climate change and about social, economic and environmental change. That makes it necessary to consider a range of possible futures when assessing climate impacts, and whether adaptive responses are needed.
Future scenarios can be developed and combined with expert knowledge and models of the sensitivity of natural or managed systems to climate. This will help determine the likely quantitative effects of climate change on council activities and services.
Scenarios can be developed for preliminary assessments, as outlined over the next few pages, and for more detailed risk assessment studies.
Three broad categories of scenario can be considered:
- Social: Demographic changes are likely to have a significant influence on the demand and supply of local government functions and services, and consequently on natural resources managed by local government.
- Economic: Agricultural, industrial and tourism development all have consequences for local government and the resources they manage. Changes in land use could have significant effects on demand and supply for resources such as water.
- Physical / environmental: Projected future climate change.
Councils will have other sources of information on future scenarios regarding social and economic changes. The information in this guide on future climate change scenarios should ideally be combined with social and economic scenarios in order to paint the most accurate picture possible.
Stage Two: Preliminary assessment of the impact of climate change
A preliminary assessment of the effects of climate change can be carried out at relatively low cost and
effort at the design and planning stages of a major project, because it can be integrated into the project development phase. Separate analyses at a later stage are likely to be more costly and less effective, as
is action to reduce future risk after the project has been completed.
Table 6 provides guidance on developing scenarios for preliminary assessments and for more detailed risk assessments. It provides suggestions, not firm scientific predictions, for scenario analyses. Especially for strong winds and heavy rainfall, projections are likely to be revised as science and modelling develop further.
Table 6 should provide planners and engineers with useful initial estimates to test the likely significance
of climate change on specific council functions and services. This preliminary assessment may not require independent expertise and can be carried out as part of a larger planning exercise at minimal cost.
For preliminary assessment purposes, the second column in Table 6 outlines how to obtain region-specific values of climate parameters: these are based largely on figures provided in Part One of this guide. The emphasis is on mid-range climate projections. If the preliminary assessment indicates significant climate change impacts or opportunities, a more detailed risk assessment is recommended. That may require a more complex physical or statistical modelling approach: using detailed analyses of current climate statistics in a location, and covering the high and low extremes of predicted climate change over timeframes that are relevant to the particular function or natural resource being addressed. If the preliminary assessment does not suggest significant effects, it is advisable to repeat the exercise using the upper range figures. It may also be useful to examine historical data. This could involve a statistical analysis or use of past events (floods, droughts, hot years etc) with additional changes in the underlying average climate, as indicators of what might happen in future.
Table 6: Values or sources of climate parameters suggested for use in scenario analyses
| Climate factor | For screening assessment scenarios | For detailed study scenarios |
|---|---|---|
| Mean temperature | Mid-range 2040 and 2090 projections (Figure 1; central values from Table 2) | Low, mid and high scenarios from ranges given in Table 2, or approach a science provider for regional numbers |
| Frost occurrence | For 2090, two top panels of Figure 2.8 in the source report. For 2040 use mid-range CLIMPACTS1 (or move current seasonal frequency distribution of daily minimum temperature right by seasonal mean change) | Use CLIMPACTS to develop low / medium / high scenario frost changes, and/or approach a science provider for regional numbers |
| Extreme high temperatures | For 2090 use lower two panels of Figure 2.8 in the source report | Use CLIMPACTS to develop low / medium / high scenario maximum temperatures and/or approach a science provider for location-specific weather generator results |
| Growing degree days | Use CLIMPACTS for a mid-range scenario | Use CLIMPACTS to develop low / medium / high scenario changes and/or approach a science provider for location-specific projections |
| Winter chilling | Approach a science provider for weather generator based location-specific projections | |
| Mean rainfall (annual, seasonal) | Mid-range 2040 and 2090 projections (Figure 2 and Figure 3; central values from Table 3) | Low, middle and high scenarios from ranges given in Table 3 |
| Heavy rainfall | Use factors from Table 7 with 5, 10, 50, 100-year average recurrence interval (ARI) values from HIRDS2 or from local data analyses | Obtain assistance from a science provider with site-specific applications of the gamma function analysis outlined in Appendix 3 of the source report |
| Flood | Use factors from Table 7 with the rainfalls used to drive the design floods | Approach specialist hydrologist for targeted advice |
| Water deficit (for irrigation) | Use weather generator in CLIMPACTS for locations of interest, for low / middle / high greenhouse gas scenarios | |
| Snow | Assume snowline rises by 140 m for each 1°C increase in annual average temperature | Requires research and development of linked spatial weather generator / snow budget modelling software for future projections |
| Strong winds | Increase 99th percentile wind speed by 10% for 2090 | Changes in the frequency of strong winds and average recurrence interval of damaging winds are still very uncertain. Consult with a science provider if screening indicates possible problems |
| Sea level, coastal hazards | Refer to Coastal Hazards and Climate Change guidance manual | Refer to Coastal Hazards and Climate Change guidance manual |
1 CLIMPACTS is an integrated assessment model for conducting analyses of the sensitivity of New Zealand’s managed environments to climate variability and change. See www.climsystems.com/
2 HIRDS is the High Intensity Rainfall Design System, available from NIWA on CD-Rom.
Consideration of heavy rainfall in assessing the effects of climate change
Heavy rainfall is a key variable in infrastructure planning and design. Table 7 shows recommended percentage adjustments per degree of warming to apply to extreme rainfalls; values are given for various average recurrence intervals (ARIs) and for rainfall durations from less than 10 minutes up to 72 hours. Current extreme rainfall rates for selected locations, durations and ARIs can be obtained from analysis of historical rainfall data sets from particular sites or from the High Intensity Rainfall Design System (HIRDS) CD-Rom (available from NIWA). The projected changes in annual mean temperature are listed in the right-hand columns of Table 2 of this guide.
Using these data, at least two screening calculations should be undertaken: one for low and one for high temperature change scenarios. A worked example of the application of this information is provided in Appendix 4 of the source report. In carrying out site-specific analyses, consider the uncertainties in return period estimates for the present climate. In many places rainfall records only cover a past period of a few decades. So, any design rainfall estimates for 50 or 100-year ARIs will contain statistical assumptions and data-based uncertainties.
As mentioned before, increases in rainfall intensity do not necessarily imply an increase in annual rainfall totals, as there are likely to be changes in the frequency of storm events. The use of the range of figures provided below may indicate that climate change could significantly affect a council function or service, and this function or service is of sufficiently large scale or importance to warrant attention. In that case, a full risk assessment using more complex scenarios may need to be undertaken.
Table 7: Factors for use in deriving extreme rainfall information for preliminary assessment scenarios
ARI = Average Recurrence Interval
ARI (years) Duration |
2 |
5 |
10 |
20 |
30 |
50 |
100 |
|---|---|---|---|---|---|---|---|
< 10 minutes |
8.0 |
8.0 |
8.0 |
8.0 |
8.0 |
8.0 |
8.0 |
10 minutes |
8.0 |
8.0 |
8.0 |
8.0 |
8.0 |
8.0 |
8.0 |
30 minutes |
7.2 |
7.4 |
7.6 |
7.8 |
8.0 |
8.0 |
8.0 |
1 hour |
6.7 |
7.1 |
7.4 |
7.7 |
8.0 |
8.0 |
8.0 |
2 hours |
6.2 |
6.7 |
7.2 |
7.6 |
8.0 |
8.0 |
8.0 |
3 hours |
5.9 |
6.5 |
7.0 |
7.5 |
8.0 |
8.0 |
8.0 |
6 hours |
5.3 |
6.1 |
6.8 |
7.4 |
8.0 |
8.0 |
8.0 |
12 hours |
4.8 |
5.8 |
6.5 |
7.3 |
8.0 |
8.0 |
8.0 |
24 hours |
4.3 |
5.4 |
6.3 |
7.2 |
8.0 |
8.0 |
8.0 |
48 hours |
3.8 |
5.0 |
6.1 |
7.1 |
7.8 |
8.0 |
8.0 |
72 hours |
3.5 |
4.8 |
5.9 |
7.0 |
7.7 |
8.0 |
8.0 |
Notes: This table recommends percentage adjustments to apply to extreme rainfall per degree Celsius of warming, for a range of average recurrence intervals. The percentage changes are mid-range estimates per degree Celsius and should only be used in a preliminary assessment. The entries in this table for an event of 24 hours’ duration are based on results from a regional climate model driven for the A2 IPCC emissions scenario (see Appendix 2 of the source report for more information on IPCC emission scenarios). The entries for 10-minute duration are based on the theoretical increase in the amount of water held in the atmosphere for a 1°C increase in temperature (8 per cent). Entries for other durations are based on logarithmic (in time) interpolation between the 10-minute and 24-hour rates. Caution: Preliminary analysis of NIWA regional climate model results indicates that in some areas increases substantially higher than the upper limit of 8 per cent given in this table are possible.
Stage Three: Detailed risk assessment of climate change effects using complex scenarios
A sound risk assessment process is fundamental to ensuring that climate change is appropriately factored into planning and decision-making processes. The risk assessment process described here is based on the New Zealand Standard for Risk Management, AS/NZS4360, which recommends a scenario-based approach (see sections 4.2.3 and 6.5 of the source report for more detail).
The purpose of risk assessment, in the context of climate change, is to identify risks and hazards caused or exacerbated by climate change and to evaluate their effects and likelihood. This also allows climate change risks and responses to be prioritised with confidence and compared equitably with other risks, resource availability and cost issues.
Because of the uncertainties involved in climate change, a mixture of quantitative and qualitative information should be used. Detailed assessments of the effects of climate change on council functions and services can be approached in any one of three main ways:
- Modelling: Computer-generated scenarios of climate change, using either existing models and data, or historical data such as past flood events to determine possible effects in the future.
- Expert opinion: Expert advice on plausible scenarios of climate change in a particular region. If, for example, flooding was used in a modelling approach, quantitative analysis could be combined with expert opinion. Lack of data and modelling capability may increase reliance on expert opinion.
- Monitoring: The real effects of climate change will only emerge through ongoing monitoring and may be the only way that effects can be quantified over time.
In selecting the approach to take, judgment is required as to which is most applicable to the specific problem or issue. Considerable capability – in terms of expertise, data and quantitative models – already exists for assessing physical impacts. For example, there is a strong capability in New Zealand for predicting river flows but there is generally a much lower capability for quantitative assessment of biological and social / human impacts. In areas such as asset management, where investment in infrastructure is required, quantitative modelling is the recommended principal approach. A combination of approaches, especially monitoring, might be used for addressing biodiversity issues.
Uncertainties or assumptions will be inherent in whichever approach is selected. These need to be taken into account, together with the uncertainties in projections of future climate, when assessing climate change effects.
Six steps to risk assessment
A six-step, scenario-based process for risk assessment is explained in detail in the source report on which this report is based. In summary, these steps are:
1. Establish the context
Define from a strategic, organisational and climate change risk assessment context for what assets, services and functions the local authority has responsibility. Consider which of these may be affected by climate change. Specify what precise service and function is being considered, and what its context is; include community expectations about the level at which this service should be delivered (including comfort levels for delay and/or exceedance, damage from malfunction etc). This context is necessary to decide whether the effect of climate change will be significant.
2. Identify hazards and describe the risks
Develop hazard event scenarios for each locality (land use, natural resource, type of development and council services provided) and/or activity, with specific assumptions about the community context; and use current and historical information to describe the risks.
3. Analyse the risks
Analyse the risks presented by the hazard event scenarios over the lifetime of the development, asset or infrastructure and their degree of likelihood, to separate minor acceptable risks from major risks and to provide data to help evaluate and treat the risk.
4. Evaluate the risks
Use risk analysis findings to categorise for each time step of the asset / service’s lifetime (ie, 25, 50, 75, 100 years):
- the risk likelihood (almost certain / likely / probable / likely / rare)
- the level of risk (extreme / high / moderate / low / negligible)
- its consequence (catastrophic / major / moderate / minor / insignificant).
5. Assess appropriate responses based on the risks
Having assessed the implications and risk of climate change, place particular types of climate change risks in context by comparing them to both other types of risks and to each other. Respond as appropriate to priority climate change risks within the context of statutory and other responsibilities, including responsibilities to consult and plan ahead.
6. Communication, consultation, monitoring and evaluation
Ensure there is ongoing:
- communication and consultation with internal and external stakeholders
- monitoring of climate change, the associated risks and the effectiveness of any risk treatment plans, strategies and control measures
- review of risk in light of changing climate change projections in order to ensure risk management plans remain relevant.
Case studies
Illustrated below are three different scenarios of varying complexity that have been used in climate change risk assessment.
Case Study 1: Southland water resources
Environment Southland identified three main drivers of change that would affect Southland’s freshwater environment in future:
- Environmental: The greatest change has been an increase in the average minimum temperature over the past 40 years. The daily temperature range is decreasing faster than elsewhere in New Zealand.
- Population: The populations of urban and rural areas have been declining since the late 1970s.
- Economic: Agriculture accounts for 82 per cent of the total land area in the region that is not conservation land. Agricultural activities are the largest contributor of nutrients, microbiological and other contaminants to freshwater resources.
Changes in land use can have a major effect on resultant environmental pressures. Over the past decade there has been a rapid expansion of dairy farming and associated industry infrastructure. Tourism is among other economic activities that could increase pressure on freshwater resources.
Thus, if Environment Southland intended studying the possible effects of climate change on Southland’s freshwater environment, it would need to consider changes in these key drivers over the next 30 to 100 years. This would require some consideration of alternative scenarios for each driver, as outlined below in Table 8.
Table 8: Examples of possible alternative scenarios for key drivers affecting southland freshwater resources
| Scenario | Environment | Population | Economic |
|---|---|---|---|
| 1 | Low-case scenario of climate change:
|
Downward trend in population stabilises with low growth over the next 50–100 years | Moderate land use changes with slightly warmer and drier average conditions |
| 2 | High-case scenario of climate change:
|
Downward trend in population stabilises with more rapid growth over the next 50–100 years due to more favourable climate (particularly for the agricultural sector such as dairy farming) | Greater intensification of land use with warmer, wetter conditions |
Case Study 2: Water resources changes in three river catchments
In 2001 the Ministry of Agriculture and Forestry commissioned Lincoln Environmental and NIWA to quantify the potential change in agricultural water usage and availability due to climate change, and to assess the implication of these changes on the potential pressures on water sources and water allocation issues.
Changes in three river catchments were studied: Rangitata in South Canterbury, Motueka in Nelson and Tukituki in Hawke’s Bay.
Environmental (climate and river flow changes) and economic (land-use changes) scenarios were developed, though the land-use changes were generated principally from the projected climate changes.
The main steps in the development of climate and river flow change scenarios were:
- gathering of historical climate and river flow data for 1971–95 for selected sites in each catchment
- generation of two climate change scenarios for 2050, and site changes (monthly) for precipitation, maximum temperature, minimum temperature, dew point temperature, and wind
- use of a weather generator to synthesise 30 years of daily climate data for 2050 for key sites
- river flow scenarios.
Land-use changes in each of the three catchments were determined by calculation of changes in mean monthly degree-days, combined with local expertise.
Current economic trends for different crops and farming systems were applied, on the basis that they would hold for 2050. The general pattern presented was for more intensive land use. The scenarios of climate, river flow and land-use change were then brought together to quantify possible changes in water demand and supply, using an irrigation scheme simulation model.
Case Study 3: Stormwater and wastewater effects in North Shore City
A study by North Shore City Council on its wastewater system included examination of the possible effects of climate change on future wet weather overflows.
Existing system performance was translated into expected future performance based on changing rainfall (extreme events) using a statistically established relationship between existing rainfall patterns and existing system performance.
Key aspects of the development of scenarios included:
- the use of 17-year historical rainfall records to determine the existing condition of the receiving environment
- the use of NIWA studies showing likely increases in temperature and rainfall due to climate change
- estimation of storm characteristics in 2050 from the historical records and historical and predicted future rainfall.
The study acknowledged that climate change is well accepted worldwide. However, the effect on North Shore’s wastewater system was based on a number of simplified assumptions with inherent uncertainties associated with modelling the effects of climate change. The study recommended that the results, therefore, should be used to assess trends rather than to provide absolute values.
