Climate change is a health issue

This section explains how climate change can affect health, potential health impacts in New Zealand, and who might be most at risk.

Many experts are concerned that climate change is “the biggest global health threat in the 21st century” [1].

On this page

How climate change can affect health
Long-term monitoring of New Zealand’s climate-sensitive health effects
Some populations will be affected more than others

How climate change can affect health

There are three ways that climate change can affect health [2]:     

1. Direct health effects

Direct health effects refer to injuries or deaths caused by the climate itself.  Examples include:

  • ‘heat stroke’
  • drowning in a flood or storm.

2. Indirect or secondary health effects

Indirect or secondary health effects are from changing biological processes.

  • Water-borne ‘tummy bug’ diseases like giardiasis and cryptosporidiosis, as well as salmonellosis, are all predicted to increase with changing rainfall, drought, and temperature patterns. 
  • Food and drinking water availability is likely to change when areas are severely affected by drought. 
  • Increases in mosquito-borne diseases like malaria and dengue fever are being seen in some areas of the world. This is not likely to be a problem for New Zealand in the near future. 

3. Diffuse health consequences

There are diffuse health consequences for people who are forced to substantially change their lives as a result of climate changes. These include:

  • mental health problems
  • displacement (when people are compelled to move away from home, for example, by sea level rise)
  • conflict.

New Zealanders will experience some of these health effects, although many other countries are likely to have more health consequences than New Zealand.

Long-term monitoring of New Zealand’s climate-sensitive health effects

Health experts believe that we will see rates of cryptosporidiosis and giardiasis change as a result of more time spent in drought conditions. We need longer-term health data before we can conclusively say whether New Zealand is seeing such effects as a result of climate change.

We reviewed notifications of cryptosporidiosis and giardiasis (Figure 1), which are believed to be related to rainfall patterns [3].  

The apparent increase in cryptosporidiosis cases from 1996 to 2013 primarily reflects improving notification rates from 1996 to 1999 as a new surveillance system was introduced. 

Figure 1

Salmonellosis is another climate-sensitive disease.  Studies show there are more notifications with an increased mean monthly temperature [4]. New Zealand data since 1996 show an overall decrease in salmonellosis (Figure 2) which is thought to be primarily due to improved food safety practices.  

Figure 2

Download factsheet on pdficon small health effects of climate change

Some populations will be affected more than others

Experts believe that some groups of people will be more vulnerable than others to the effects of a changing climate. 

Vulnerability to climate change can be related to:

  • increased exposure to climate change
  • sensitivity to its effects
  • reduced capacity to adapt to climate change.

Examples of how particular groups could be more vulnerable include:

  • Young children and older people are more sensitive to dehydration on very hot days.
  • People on low incomes generally have fewer resources to protect themselves from extreme weather.  For example, they may not have a car to move away from a flood risk. 
  • Māori, like indigenous populations in other countries, are more dependent on primary industry economies (like farming) that are sensitive to climate changes [5,6]. If there is an increase in drought, Māori will be more heavily affected.

In the New Zealand context, populations vulnerable to climate change include:

  • young children (aged under 5 years)
  • older adults (aged 65+ years and 80+ years)
  • Māori
  • ethnic minorities
  • those who live in poverty
  • those with chronic health problems
  • those with a disability
  • refugees.

In New Zealand, data from the census can provide information about vulnerable populations in each area.  

See relevant information in the population section of the website.

We can also look at this data alongside climate-related data to consider how much impact a changing climate might have on people in a region.

If we know what vulnerable groups exist in an area, and how big those groups are, we can anticipate what additional supports might be needed to help these groups adapt to climate changes.  

Download factsheet on pdficon small New Zealand population and ethnicity.


1. Costello A, Abbas M, Allen A, Ball S, Bell S, Bellamy R, et al. 2009. Managing the health effects of climate change. The Lancet 373(9676): 1693-1733. doi: 10.1016/S0140-6736(09)60935-1

2. McMichael AJ. 2013. Globalization, Climate Change, and Human Health. New England Journal of Medicine 368(14): 1335-1343. doi: 10.1056/NEJMra1109341

3. Lal A, Baker MG, Hales S, French NP. 2013. Potential effects of global environmental changes on cryptosporidiosis and giardiasis transmission. Trends in Parasitology 29(2): 83-90. doi: 10.1016/

4. Britton E, Hales S, Venugopal K, Baker MG. 2010. Positive association between ambient temperature and salmonellosis notifications in New Zealand, 1965-2006. Aust N Z J Public Health 34(2): 126-129. doi: 10.1111/j.1753-6405.2010.00495.x

5. Te Puni Kōkiri. 2012. The Māori Economy. Wellington: Te Puni Kōkiri.

6. Te Puni Kōkiri. 2007. A Time for Change in Māori Economic Development. Wellington: Te Puni Kōkiri.