Climate change and heat stress

As the leading scientific research is telling us (the Intergovernmental Panel on Climate Change, the United Nations Environment Program, the World Meteorological Organisation, National Oceanic and Atmospheric Administration) climate change is real and accelerating.

Right now, we are on track for catastrophic climate change – at least 3 degrees of heating and maybe more.

Our own CSIRO and Bureau of Meteorology advise that Australia is now 1.44 degrees hotter than when records began in 1910. Australia’s warmest (and driest) year on record was 2019, and the seven years from 2013 to 2019 all rank in the nine warmest.

Warming is observed across Australia in all months with both day and night-time temperatures increasing. This shift is accompanied by more extreme nationally averaged daily heat events. For example, 2019 experienced 43 extremely warm days, more than triple the number in any of the years before 2000. This increasing trend is observed at locations across Australia.

Future trends

In the future what we can expect includes:

A decrease in cool season rainfall across many regions of the south and east, likely leading to more and longer droughts
Continued warming, with more extremely hot days and fewer extremely cool days
Increased frequency and duration of heat waves
A longer fire season for the south and east and an increase in the number of dangerous fire weather days
Fewer tropical cyclones, but a greater proportion of high intensity cyclones, with ongoing large variations from year to year
Fewer east coast lows particularly during the cooler months of the year

Impact on our animals

In summer we now see a greater frequency of very hot days compared to earlier decades. In terms of national daily average maximum temperatures, there were 33 days that exceeded 39 degrees in 2019, more than the number observed from 1960 to 2018 combined, which totalled 24 days.

While the science is indisputable in the last quarter century or so, we’ve been making it even harder for our animals to cope.

Many areas of management, selective breeding, nutrition and environmental controls,have aimed to make our animals “more productive”. The result is often fast growing and “ high yielding “animals which already have higher, internal heat loads. All of this increases their sensitivity to hot environments”.

The temperature comfort zone for cattle, pigs and goats is much lower than it is for humans. Dairy New Zealand notes that dairy cows (crossbreeds as well as friesians) begin to experience the effects of heat stress when temperatures reach 21 degrees and more than 70% relative humidity.

The RSPCA describes a “thermoeutral zone” a preferred temperature range for animals. For beef cattle (British breeds) it is 15 – 25 degrees, beef cattle (tropical breeds) 16 – 27 degrees, dairy cattle 5-20 degrees, goats 10 – 20 degrees, pigs 16 to 25 degrees and sheep 21 – 31 degrees.

“Dairy cattle will seek shade (at temperatures above 21 degrees) and increase water intake by 1.2 litres for every degree above minimum ambient temperature indicating their need for additional water and shade.

An increased need for water will occur as climate change simultaneously makes cool drinking water scarce. In extreme cases, animals’ mental state can be altered by hyperthermia and they may be incapacitated from seeking out essential resources even where they are available”.

Animals under stress

According to the RSPCA, “Climate change puts the welfare of Australia’s estimated 800 million farm animals at risk. Heat stress has been described as one of the most pressing challenges facing animal agriculture”.

“In a changing climate, more farm animals across a wider area will be subject to heat related illness and associated negative affective states including thirst, frustration and discomfort.”

The climate science is clear. Temperatures are rising. The Bureau of Meteorology reports that spring and November 2020 were the warmest on record for Australia. Spring temperatures last year were 2.03 degrees above average.

These are some of the many, documented behaviours that indicate when an animal is suffering heat stress:

search for shade and water
stay close to water – crowd around a water trough
stop eating
refuse to lie down
become restless, agitated, frenzied or lethargic, depressed
stepping, pawing the ground
ears back
laboured breathing, panting, tongue lolling, drooling
head up, neck extended
convulse, collapse

For cows, increased ambient temperature increases the risk of lameness, immune suppression and metabolic disorders. It decreases food intake which can cause weight loss, lethargy and malaise.

“Cattle, sheep and goats have unique physiology which makes them susceptible to a suite of complex animal welfare issues associated with climate change. Increased ambient temperatures place ruminants at higher risk of debilitating conditions. Higher ambient temperatures have been linked to painful lameness via mechanisms including: increased standing time, decreased time lying down, ruminal acidosis (increase in stomach acidity) from altered feed intake, respiratory alkalosis (decrease in blood acidity due to increased respiration rate) and altered energy balance. Higher ambient temperatures are associated with higher livestock mortality rates and in some cases, mass deaths, ” the RSPCA reports.

Young, old, pregnant or lactating animals are even more vulnerable, as are those with pre-existing conditions.

Solutions are clear

According to the Qld Department of Agriculture – “ Shade can reduce a cow’s heat load from the environment by up to 50%. Allow access to shade throughout the day. Provide shade in feed-out areas, grazing areas and over the milking yards”.

Research from organisations like the Meat and Livestock Australia, departments of agriculture through to the RSPCA all show this clearly – shade/shelter is essential to reduce heat stress in animals.

Despite that, there are no mandatory requirements for owners and carers of animals to provide adequate shade/shelter. There is no minimum standard for shade/ shelter.

“This results in severe suffering”, according to Australian-born veterinarian Andrew Knight, Professor of Animal Welfare at Winchester University in the UK.

“All farm animals are sentient, sensitive animals, capable of feeling pain, stress and fear”. Being exposed to excessive sunlight can be highly stressful and decrease their health and welfare. Such systematic lack of care is indicative of the widespread exploitation these animals endure.”

Please take action to help protect our farm animals.