Climate–land-use dynamics in high and hill country environments: implications for conservation, primary production, rural communities, and ecosystem services
General Context (from MBIE contract)
Climate change will have direct impacts on hill & high country environments via 1) changes to primary production; 2) native forest & shrubland successional dynamics; and 3) increased pressures on sensitive ecosystems such as ephemeral wetlands. It will also have indirect impacts to ecosystem services (e.g. water quantity & quality, soil erosion, carbon dynamics and sequestration). This modelling will explore the potential implications for conservation, forestry, bioenergy, and pastoral sectors including such issues as water allocation and irrigation, risk of wildfires, associated economic costs & benefits, and potential policy responses.
By the middle of this century water and air temperatures are expected to be, on average, around a degree Celsius higher than was the case in the 1990s. Toward the end of the century the mid-range projections are for an increase of 2oC and may be as high as 5oC. Average rainfall is expected to increase in the west and south and decrease in the east and north, and heavy rainfall events may become more severe. This might be expected to influence a range of issues relating to primary productivity, ecosystem services and conservation.
Effects on upland systems will be a combination of direct impacts of climate change, changes in social and economic conditions due to climate change, and impacts of policies for greenhouse gas reductions or climate change mitigation.
Study Area Selected
The Uplands Case Study will encompass iconic areas of high country of the Mackenzie Basin and surrounding watersheds. The study area will be defined as the upper part of the Waitaki River catchment, including all areas draining into the reservoir Lake Waitaki. The case study will use the boundaries of the Upper Waitaki Zone of the Canterbury Water Management Strategy of the Canterbury Regional Council, as the precise definition of the boundaries of the study area (see the Canterbury Water Zone Map).
Potential Impacts of Climate Change
The following impacts of Climate Change are currently under consideration within this Case Study. The final choice of issues, and the emphasis and effort amongst them will be chosen by ongoing input from a range of stakeholders.
- Flow availability and hydrological fluxes for downstream users as well as any other hydrological variables (eg snow cover area, groundwater recharge, surface runoff, evaporation from soil-vegetation-“snow sublimation”) as well as extreme events (eg flood event, drought occurrence).
- Land-use change and its downstream impacts
- Agricultural profitability
- Agriculture and forestry production impacts
- Wilding pines and wildfires
- Shifts in environmental conditions and resulting shifts in ecosystems, including species distributions and exacerbated increased weed invasions
Potential Implications of Climate Change
The case study will attempt to explore the implications of climate change primarily through the use of farm systems and landuse models, with the understanding that there is likely to be a “nesting effect” of impacts and implications. For example, an impact of changes in rainfall and runoff to streams and rivers in the catchment could be a change in the potential to extract and store water for irrigation. This will have implications for pasture productivity in the area, which will have associated implications for farm profitability, which then may have an impact on landuse. This “nested” impacts/implications concept will be explored in this case study.
Highlights of the Synthesis Report: RA2 Uplands Cast Study
- The Uplands Case Study undertook loosely coupled systems modelling to better understand the potential impacts and implications of climate change for the economy, environment and society in the upper Waitaki catchment from an integrated perspective. Systems modelling was used to evaluate scenarios linking global development organised along socioeconomic and representative greenhouse gas concentration pathways with selected aspects of New Zealand development both nationally and sub-nationally, e.g. the upper Waitaki catchment.
- Impacts and implications of climate change in the catchment will result from both direct and indirect effects of a suite of interacting biophysical, socioeconomic and cultural drivers operating across global, national, regional, and local scales.
- The regional climate including the study area is likely to become warmer and wetter, with some shifts in seasonal patterns. The number of hotter days ≥ 25°C and colder nights ≤ 0°C is likely to increase and decrease, respectively. Frequency of extreme events such as high rainfall or winds could increase as much as 10 to 15%, depending upon the magnitude of future global greenhouse gas concentrations.
- Global and national socioeconomic developments, such as changing commodity prices, will strongly influence the catchment. In some cases, those developments will outweigh the direct, local effects and impacts of climate change in relation to land-use change.
- The warming climate and changing precipitation and weather patterns is likely to increase the availability of suitable area for many weeds and reduce suitable area for some. Changes are very likely to vary over time, with some effects felt earlier than others. The shifting patterns of balance and timing will increase challenges to biodiversity and conservation management by shifting management and control priorities and possibly increasing the total pressure exerted by weed species on both native biodiversity and primary production.
- Hydrological modelling shows that water management will likely become more challenging and complex. While mean annual flows in the catchment are likely to undergo small average changes over the coming century, mean seasonal flows will likely show more pronounced changes, reflecting changes in weather patterns resulting from climate change. Changes in the seasonal patterns will affect the timing of storage and delivery of water for a range of uses.
- Annual pasture productivity is likely to increase overall due to increased plant growth resulting from the likely increase in precipitation and water availability and CO2 fertilization effects from higher atmospheric CO2 concentrations. Large seasonal changes, including summer feed gaps and more productive winters, could necessitate adaptation to shifts in the temporal availability of forage for livestock.
- Although not explicitly modelled, expected trends in climate change will likely have negative implications for tourism and recreation. For example, reduced snowfall and/or the ability to operate snow-making equipment could over time reduce the net number of days suitable for skiing in the catchment. Also, higher frequency of extreme events could increase risks of damage to important tourism infrastructure such as huts and tracks.
- Expansion of the range of wilding conifersould likely decrease water yield relative to current vegetation cover and help mitigate the increasing wildlife risk from climate change. However, that expansion is very likely to impact negatively on native biodiversity and primary production in complex ways, e.g. further invasion of tussock grasslands would reduce the extent and ecological integrity of native ecosystems and areas remaining in primary production.
- In summary, the uplands case study demonstrated that climate change, when considered in conjunction with broader socioeconomic developments, will likely increase uncertainty and risks and therefore increase challenges to policy, business planning, resource management, and societal resilience into the future. The ability to cope and adapt to changing risk profiles varies among scenarios and depends both on assumed socioeconomic developments as well as on the expected degree of climate change.
Click here to download the RA2 Uplands Case Study Synthesis Report.