Climate-land use dynamics in lowland environments: implications for conservation, primary production, urbanisation and ecosystem services
General Context (from MBIE contract)
Climate change will impact important primary sectors such as dairy, horticulture, and arable cropping, as well as ecological functioning of native ecosystem remnants. Expected increases in land-use competition and intensification will compound these impacts. This modelling will explore the potential implications of the dynamics among conservation, primary production and urban land uses. It will also explore the associated implications for native biodiversity in fragmented landscapes, long-term availability of high quality soil resources for agricultural production and effects of land use intensification on water resource management.
Study Area Selected
After evaluation against preselected criteria and engagement with Bay of Plenty Regional Council, the Lower Kaituna (including part of Papamoa) has been selected for this case study. This area is likely to be affected by both drought and flood related climate issues, contained all ten of the evaluated land uses (conservation, urbanisation, intensification, freshwater wetland, native forest, dairy, forestry, cropping, horticulture/viticulture, urban), and connections with Iwi and Regional Council were already established.
Potential Impacts of Climate Change
The following factors are potential impacts of climate change in the lowland environments:
- Droughts: drier conditions in eastern New Zealand can lead to water shortage in rivers with increased pressure on water resources.
- Floods: the increased frequency of storms can lead to flooding, landslides, mudslides, increased soil erosion, increased pressure on government and flood insurance, and increased pest and disease.
- Change in average temperature: lead to change in suitability for certain land-use types.
- Change in CO2 concentration: increase or decrease in annual pasture yields. This may also favour certain native plants or weeds and instigate a change in species composition or abundance.
- Moisture stress: decline in milk production, reduction in stock numbers, sun-damage on fruits, reduction in aquatic environments
- Increased pressure and decreased resilience mean both native ecosystems and production environments may be more susceptible to pests and diseases.
- Social and financial limitations may constrain changes (or rate of change) in land use in response to environmental changes (i.e. current land uses may not be fitting post climate change but people may be unwilling or unable to afford to alter how they use the land).
Potential Implications of Climate Change
Potential changes to water flows are likely to have implications for irrigation demand and associated costs of water management, while any changes in water quality due to changed landuse will have implications for environmental regulation, associated costs, and freshwater ecosystem services. Further implications of changes in landuse or land-based productivity may include changes in economic return for some farming systems, leading to the potential for landuse change with associated societal implications. Future flooding frequency and sea level rise impacts are likely to have significant implications for protective infrastructure upgrades, requiring continuing assessments of hazard lines, and the potential for setbacks from hazardous locations.
Highlights of the Synthesis Report: RA2 Coastal Case Study
- In the Bay of Plenty, there will be a likely increase in mean air temperature and number of hot days and dry days, increasing the risk of drought.
- There is likely to be more rain in summer and less in winter and spring.
- Sea level rise will affect the coastal zone around the Kaituna catchment, with 5,500 ha likely to be regularly inundated every couple of weeks during high tide (1.8 m above mean sea level) affecting the dairy industry and maize cropping.
- Change in pasture production is positive under all scenarios for both sheep and dairy pasture. The magnitude of the change is larger for dairy than for sheep. Total annual pasture growth increases by 1–5 % around mid-century and by 2–7.5% by 2100. Seasonal average growth rates show consistent, large increases in winter and spring, as expected under warmer conditions and an extended growing season.
- For forestry, simulations with constant CO2, there were reductions in productivity of 4–20% for both 2055 and 2085 depending on the Representative Concentration Pathway (RCP) scenario. For simulations with increasing CO2, growth increased by about 10–15% by 2055. The between-site variability was higher for the simulations with constant CO2 than for those with increasing CO2, with standard deviations by 2085 ranging from 3 to 7% for simulations under constant CO2, which reduced to 2–3% under increasing CO2. It is consistent with the general tendency for increasing CO2 to have greater beneficial effects for plants growing under otherwise more stressful conditions.
- For maize silage, the impact of climate change yields was assessed considering model runs with or without adaptation of crop genotype and sowing dates. Model results indicate a higher risk of yield losses when sowing dates are not adapted. For these conditions, yield loss estimates increase from mid-century (5%) to the end of the century (12%). In contrast, by adapting sowing dates to a warmer climate (i.e. sowing early), yield losses were minimised and yield gains occurred for specific locations. Climate change impacts on silage yield were uneven across the catchment. More negative impacts were estimated in the northern lowlands, currently the most suitable area for arable cropping.
- Hayward kiwifruit production viability for the Te Puke area is projected to decrease steadily over time and becomes consistently marginal by the 2050s and non-viable by the end of the century. The key reason for this is the loss of sufficient winter chilling as the climate warms. However, other inland North Island regions and many parts of the South Island (particularly Canterbury) show an increase in viability (based purely on temperature) for this crop variety over the century.
- Land-use change in the catchment could be significant over the next century, and is projected to be affected by both the socioeconomic pathways and climate change. The Shared Socio-Economic Pathway scenario chosen (SSP3) is projecting high log and sheep & beef prices compared with dairy prices. By comparing two land-use change models, we found that there is generally a shift from sheep & beef farming to forestry by the end of the century. High log prices cause forestry to increase beyond baseline levels in both models. However, discrepancies in model assumptions and structure meant that there were differences in dairy changes (opposite directions) and magnitude. Regardless, the consistent result of an increase in afforestation in the Kaituna by 2100 across all scenarios suggests environmental outputs such as GHG emissions and freshwater contaminant loads could be reduced over the next century, even if there is some intensification in the catchment.
- For the remaining swamps in the Kaituna, increased precipitation may induce a change in wetland type to a permanently wet state (e.g. ephemeral to swamp); a higher nutrient system (e.g. fen to swamp), or a more aquatic system (shallow water, pond or lake). Lower rainfall would increase pressure on obligate wetland plants and therefore vegetation types dominated by these species. Changes in rainfall periodicity or intensity will also have an impact, as it may increase the extent of wetland margins and thus favour facultative dryland species, many of which are alien weeds.
- An integrated assessment provided an overview of potential future impacts of both climate change and socio-economic changes. In the scenario that was investigated (high Representative Concentration Pathways (RCP), fragmented world), there is almost no attempt to curtail climate change on a global scale and only very limited, reactive local efforts. Costs of production would generally increase due to a need for increased environmental management for pest control and water shortages, with a higher risk for a decline in commodity prices due to increased global competition.
Click here to download the RA2 Lowlands Case Study Synthesis Report.