Climate Change

Regional climate risk assessment reports (produced by local authorities) include planning for the impacts of climate change on human health.

For example, Bay of Plenty Regional Climate Change Risk Assessment is based on NIWA predictions which include an increase of up to 25 “hot days” per year (>25 degrees) by 2050, and 70-80 days by 2100 for the Bay of Plenty.

Read the Regional risk assessment by Bay of Plenty Regional Council

To effectively target interventions and address vulnerability during heatwaves, it is crucial to identify the populations at highest risk.

Vulnerable groups have been identified based on susceptibility to illness, isolation, inadequate cooling, and housing, and increased outdoor exposure.

These groups include the elderly, infants and children, individuals with chronic health conditions, those of low socioeconomic status or experiencing homelessness, individuals living alone, and people with outdoor occupations.

Greenspace plays a significant role in reducing heat related harm and death from increased heat. For instance, one study found that a 20% increase in greenspace is associated with a 9% decrease in heat-related deaths from cardiovascular and respiratory diseases. Even a minor increase in tree canopy cover, from <5% to >5%, resulted in an 80% reduction in heat-related ambulance calls in Canada.

Read the effect modification of greenness on health

In March 2023, the Parliamentary Commissioner for the Environment released a report underscoring the importance of urban green space in future city planning in New Zealand. The report emphasizes the role of greenspace in mitigating climate effects and highlights the numerous benefits associated with several types of greenspaces, as shown in the diagram below. The choice of species can have large impact as there is variation between evapotranspiration rates and shading properties of different trees.

Hamilton City Council has already initiated plans to raise vegetation cover from 2% to 10% by 2050, promoting green growth throughout the city.

Greenspace and associated benefits

To reduce the urban heat island (UHI) effect in New Zealand cities, infrastructure changes can be made. There is opportunity for new buildings to be constructed with heat stress and climate risks in mind and some changes are also possible to existing structures. These building changes can be of value to new builds as it can help address inequities while being a government initiative. Here are the key measures:

Building roofs design

Roofs in the modern urban environment are the largest sun exposed surface and therefore one of the largest areas to reduce urban heat.

• Using cool roofs: Reflective surfaces reduce heat absorption and indoor temperatures, particularly effective for single-story buildings.
• Using alternative materials to thermally massive materials: Using non-thermally massive materials avoiding concrete and tile can lower indoor temperatures, but this may be more expensive.
• Rooftop solar panels: While they do not provide significant cooling, solar panels reduce energy consumption and offer shading benefits.
• Green roofs: Green roofs, covered with plants, have multiple cooling effects, and can provide insulation, evapotranspiration (process by which water moves from the land surface to the atmosphere via evaporation and transpiration), and shade from trees. However, they are expensive and challenging to incorporate into existing buildings.

Wall design

Wall design plays a crucial role in reducing the urban heat island (UHI) effect. Considerations must be made to ensure walls allow daylight, views, and avoid glare or excessive heat reflection. Here are some strategies for wall design:

• Shading with vegetation: Planting vegetation for wall shading offers effective cooling benefits. Green walls incorporate plants into the building design, but they require regular maintenance and irrigation.
• Light-coloured finishes: Using light-coloured finishes on walls helps reduce heat absorption and lower temperatures.
• Careful material selection: Avoiding thermally massive materials like concrete can minimize heat retention and contribute to reducing the UHI effect.

Pavement and roads

Pavement and roads contribute to the urban heat island (UHI) effect by absorbing and releasing heat into the surrounding air. To mitigate this effect, the following measures can be taken:

• Shading with trees: Planting trees around paved areas can provide shade and reduce heat absorption, effectively lowering temperatures. Priority should be given to areas where trees can offer maximum shading coverage.
• Cool paving: In situations where shading is not feasible, cool paving materials can be used. However, it is important to consider the potential glare caused by their reflective properties, which may not be suitable for areas with high pedestrian traffic or where it could pose problems for vehicles.

Below is a diagram form the Western Sydney Regional Organization of Councils’ “Turn Down the Heat Strategy and Action Plan” published in 2018 comparing different methods of urban cooling, their effectiveness, and key constraints of each: 

Heatwaves lead to an increase in water and energy demands as people use them for cooling purposes. Heatwaves also cause increased physical strain on the power grid, reducing generation efficiency and capacity in the transmission and distribution systems. Furthermore, heatwaves contribute to the drying of water reservoirs. This combination of heightened resource utilization and extreme heat exacerbates the strain on the availability and reliability of both water and energy resources.

To enhance power resilience during heatwaves, the following areas can be targeted:

• Increase electricity network capacity: This approach involves expanding the capacity of the electricity network, although it can be costly and may result in higher power prices, which disproportionately affect those with lower socioeconomic status.
• Reduce peak demands:
  • Lower power usage, primarily by reducing the need for air conditioning (AC) through the design of cooler buildings, as described earlier. This helps decrease the overall demand on the energy network during heatwaves.
  • Decrease reliance on the centralized network by promoting independent energy generation, such as the installation of solar panels or generators. While not feasible for everyone, many homes and commercial buildings have the potential to adopt solar panels. When coupled with onsite batteries, which are becoming more affordable, they can significantly contribute to alternative energy generation. Generators are crucial for buildings housing vulnerable residents or hospitals and serve as a backup during power outages, although they are not practical for most situations.

Implementing these measures can improve power resilience during heatwaves and help mitigate the strain on the electricity system.

To enhance water resilience during heatwaves, the following areas can be targeted:

• Reducing water demand:
  • Promote water-efficient practices like xeriscaping, which minimizes the need for irrigation, and encourage the planting of heat/drought-resistant trees and vegetation particularly prioritizing native planting.
  • Implement water restrictions on communities during short-term water crises to manage and reduce water consumption.
  • Similarly, to energy, households and businesses can reduce their dependence on the central water network by establishing their own water supplies, such as through stormwater harvesting. This approach is particularly useful for irrigation purposes. However, it is important to note that in hot regions, there are limitations to the effectiveness of these measures.

By focusing on reducing water demand and implementing conservation measures, communities can increase their resilience to water shortages during heatwaves. 

In Europe, programs were implemented to combat social isolation during heatwaves. For instance, in Italian cities, the "Long Live the Elderly" program, initiated after devastating heatwaves in 2003, involved volunteers, doctors, neighbours and others who made phone calls, home visits, delivered food, and organized public events. This program reduced hospitalization by 10-15% and residential institutionalization by 20%, leading to cost savings in social and healthcare.

A study comparing regions with and without the program found a 40% reduction in mortality. Similarly, in some Australian states, the Telecross REDi program makes phone calls to vulnerable individuals during extreme heat events and provides support.