For most of us the equation is pretty simple: too much heat = too much sun = sunburn … or worse, skin cancer or heat stroke, both possibly fatal.

So, we take the practical step of protecting ourselves from too much sun, as you might have done before reading this magazine relaxing at the beach or on a deck chair.

What about ‘planetary sunburn’ … global warming? What are its health effects?

They range from the obvious – deaths from wildfires and extreme weather events to the much less obvious, arising from ecosystem changes (e.g., ‘new’ germs and diseases), and social/economic disruption (e.g., migration stresses, malnutrition).

Nearly 20 NZ health organisations have signed the ‘Health Professionals Joint Call for Action on Climate Change and Health’, which advocates a broad mitigation programme including health sector planning to prepare for the “locked in” health impacts of climate change that are already unavoidable. 

The Royal Society of New Zealand published in a report in 2017, Human Health Impacts of Climate Change for New Zealand, resting upon some 167 footnoted sources.

It began simply: “Many of the fundamental building blocks for health and well-being are threatened by climate change.”

Globally, the impact numbers are huge: 250,000 additional deaths per year by 2030 as a result of heat exposure, diarrhoeal disease, malaria and childhood undernutrition. Reductions in global food availability, and fruit and vegetable consumption in particular, are estimated to result in a further 500,000 climate-related deaths worldwide by 2050. 

Sea rise displacement, extreme heat and destabilising water shortages will lead to severe stresses affecting health and mental well-being, if not life-threatening chaos and violence. 

In NZ, as globally, the Report notes that risks to human health associated with climate change are greatest to children, the elderly, people with disabilities and chronic disease and low-income groups. Those with the least resilience to heat, life and safety-threatening weather events, infrastructure damage and essential service disruption.

Direct impacts

The Royal Society report ticks through the direct health impacts of climate change first. 

Increased flooding, fires and infrastructure damage – these can cause impacts lasting for weeks and months. Displacement – the stress of coastal retreat. 

Then there’s the heat itself – many places in NZ will see more than 80 days per year above 25C in the future (compared to 20-40 currently). Extreme temperatures mean more deaths. The Report cites estimates from Auckland and Christchurch where it’s estimated that the number of heat-related deaths amongst those aged over 65 when temperature rises 1C, 2C or 3C over 20C would double, triple and increase five-fold, respectively. 

Add well-documented occupational health risks – from heat stroke to renal failure – amongst outdoor workers in agriculture, forestry and fishing.

Those with diabetes or cardiovascular disease are especially sensitive to heat stress.

And then there’s aggressive behavior, violence and suicide. Says the Report (with relevant citations): “Hospital and emergency room admissions increase at temperatures above 18–20 for those with mental health or psychiatric conditions. Individuals with mental illness are especially vulnerable to high temperatures or heat waves.”

Indirect issues

The Report anticipates that droughts, floods and increased temperatures will lead to water contamination and toxic algal blooms (like the highly dangerous blue-green algal blooms more frequently appearing in HB waterways like the Tukituki). “As average temperatures rise, the seasonal and geographic range of suitable habitat for blue-green algae species is projected to expand with potential impacts on drinking water supplies and recreational water use.”

Marine risks will also increase. “The projected impacts of climate change on toxic marine algae include changes to the geographic range of both warm- and cold-water species, changes in abundance and toxicity, and changes in the timing of the seasonal window of growth.” Gambierdiscus, an algae that causes illness from eating contaminated fish, could spread from Pacific Islands, where it is already a significant health problem to warming waters around NZ.

And referencing a risk Hawke’s Bay has already faced, the Report predicts: “Climate change … will increase people’s exposure to waterborne diseases caused by bacteria, viruses and protozoa, such as Giardia and Cryptosporidium … Changing weather patterns, including more extreme rainfall events, flooding, and higher temperatures, are likely to interact with agricultural run-off, and affect the incidence of diseases transmitted through infectious drinking and recreational water.”

Food availability and safety

Given the food focus of our regional economy, Hawke’s Bay might want to pay special attention to the impact of climate change on what we grow. [John van der Linden writes in this BayBuzz about global warming and winemaking.]

So, here I’ll quote the Report directly:

“Changes in air and water temperatures, rainfall patterns, and extreme events can also shift the seasonal and geographic occurrence of bacteria, viruses, parasites, fungi, and other pests and chemical contaminants. This can lead to reduced food safety prior to, during and after the harvest, and during transport, storage, preparation and consumption. For example:

• Higher temperatures can increase the number of microorganisms already present on fruit and vegetables.

• Sea surface temperature is directly related to seafood exposure to microorganisms and biotoxins.

• Extreme events like flooding have been identified as a factor in the contamination of irrigation water and farm produce, and the E. coli contamination of shellfish.

• Changing environmental conditions and soil and water properties may lead to increased levels of heavy metals in the food supply. For example, higher temperatures increase the rate of toxic methyl mercury formation by microorganisms in marine waters and sediments, with implications for elevated levels of mercury in fish. Fish are a significant source of mercury in the New Zealand diet.”

More health worries

The Report notes the impact of increased temperatures, extreme weather events (including drought) and displacement of people from their homes and communities will all have “significant mental health and well-being consequences … from minimal stress and distress symptoms to clinical disorders such as anxiety, depression, post-traumatic stress and suicidal thoughts.” It suggests these impacts might be greatest amongst our rural population, where suicide is an already-significant problem.

The impacts continue …

More fire events predicted in the east and north of NZ mean more particulate matter in the air, with associated asthma and cardiovascular ill health.

Changes in NZ climate (including more CO2 itself) will yield more pollen over longer periods and increase its spatial distribution, again a worsening condition for those with respiratory conditions.

And last but not least, carriers of new diseases. The number and distribution of organisms, not limited to mosquitoes, ticks and fleas – that can transmit infectious diseases will be affected by temperature and rainfall change. We’re conceivably facing Nile virus, dengue fever, encephalitis (these now in Australia) and Zika virus (now in Pacific Islands).

The Report concludes: “…links between climate change, mosquito populations, and the lifecycle of diseases are likely to increase the range and incidence of diseases such as malaria and dengue fever, which may become significant in areas where temperature is currently the limiting factor.”

Do we have your attention yet? Global warming is not cool!

Note: Another good NZ-specific paper, ‘Health and equity impacts of climate change in Aotearoa-NZ’, was published in 2014 in the NZ Medical Journal. You can also follow the ongoing work of the NZ Climate & Health Council ( 

Royston Hospital is pleased to sponsor robust examination of health issues in Hawke’s Bay. This reporting is prepared by BayBuzz. Any editorial views expressed are those of the BayBuzz team.

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