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Cows don't do well in the heat. Shutterstock

Climate change and extreme weather events are already impacting our food, from meat and vegetables, right through to wine. In our series on the Climate and Food, we’re looking at what this means for the food chain.

During the recent heatwave in New South Wales, which saw record-breaking temperatures for two days in a row, 40 dairy cows died in Shoalhaven, a city just south of Sydney.

Climate change doubled the likelihood of this kind of record-breaking heatwave. And even the higher minimum temperatures we’ve recently experienced may soon be the “new normal” for this time of the year.

Farmers that already find it difficult to make a profit will need to adapt to these changing conditions, ensuring they mitigate the effects on their livestock. This could take the form of more shade and shelter, but also the selection of different breeds to suit the conditions.

What’s happening?

Cattle are vulnerable to changes in rainfall patterns (variability and extremes), temperature (average and extremes), humidity, and evaporation. These climactic changes can affect livestock directly, and also indirectly through pasture growth, forage crop quantity and quality, the production and price of feed-grain as well as spatial changes in disease and pest distribution.

The greatest risks stem from extreme events such as heatwaves and droughts, as they are less predictable and much more difficult to adapt to than gradual changes.

Dairy cows are particularly affected by heatwaves, which can not only reduce milk production, but, as the NSW heatwave illustrated, cause illness or death. Further, the effects on milk production and the protein content of the milk can last for several weeks.

Similar to humans, instances of high relative air humidity and little wind worsen the negative effects of high temperatures on livestock. When this occurs, the animals cannot easily offload excess heat through transpiration. This is compounded when there is little or no cloud cover, as the cattle are exposed to more solar radiation.

Milk production is also impacted by night-time temperatures and the timing of the heatwave. When night-time temperatures are high, cows cannot offload excess heat. If a heatwave occurs after the cows’ peak of lactation, milk production is less likely to recover and the impact is even worse.

The response of cattle to heat stress also depends on the breed. This can differ as a result of, among other things, differences in metabolic rate, sweating rate, coat texture and colour. Researchers have even identified a “slick hair gene”, responsible for producing cattle with shorter, slicker hair that reduces their vulnerability to direct radiative heat. The full benefits of the slick gene still require more research as a strategy for animals to cope in future climates.

Sheep are generally less affected by high temperatures than dairy cows. However, heatwaves with temperatures beyond 40℃ can cause heat stress. Hot days may have short-term impacts on rams’ fertility, and recently shorn sheep are at risk of sunburn if they are exposed to direct sunlight.

Factors that are unique to each individual animal, such as previous heat exposure and overall health and age, also play a role in how vulnerable they are to heat.

Mitigation

In the short run, farmers can mitigate the worst of these issues by providing high-quality water and shade (such as from trees, buildings, and shade cloth) in the heat, warm shelter in the cold, and by adjusting feed. During heatwaves, farmers can also adjust milking procedures and milk their cows very early in the morning or late at night. To provide immediate cooling they can also use sprinklers or misting systems. But care is needed to avoid simply increasing humidity around the animals.

Mitigation can be as simple as providing a bit of shade. Shutterstock

A more long-term option is to selectively choose breeds that are better adapted to higher temperatures (such as breeds with lighter coat colour or Bos indicus types or crosses). Unfortunately, breeds adapted to warmer climates, such as the Brahman, tend not to be high milk producers or to do as well in feedlots as the traditional British beef breeds, so there will be a hit to productivity.

As the impact of climate change isn’t solely on the animals themselves, farmers will also have to adjust their work patterns and other aspects of their operations. To cope with heat, farmers themselves may need to consider working more during the cooler hours of the day. Farming both crops and livestock together can also provide a buffer against the impact of an extreme event. The combined production of wheat and wool is a typical example of spreading of risk on farm.

But for these strategies to really be effective, farmers need more information.

This includes accurate and timely forecasts of weather (temperature, rainfall, solar radiation) and heat (such as the temperature humidity index, THI) at daily, weekly and seasonal scales. Armed with this data, farmers and livestock managers can effectively plan and implement protection measures ahead of time.

A wide range of agricultural, climate and weather services exist. For example, the Bureau of Meteorology weather forecasts, seasonal outlooks of rainfall and temperature, and the current water balance and soil moisture information. There’s also the the Cool Cows website, the Dairy Forecast Service and the Cattle heat load toolbox.

We also need more research into improving our understanding of the climate system, to develop risk management plans for industries by regions, and more accurate and reliable forecasts, so that farmers and livestock managers can make management decisions and ensure the wellbeing of themselves and their animals.

Elisabeth Vogel receives an Australian Postgraduate Award for her PhD studies. She is affiliated with the Australian Research Council Centre of Excellence for Climate System Science.

Christin Meyer receives a scholarship from Süedwolle GmbH for her thesis and is enrolled as PhD student at the Potsdam Institute for Climate Impacts Research in Germany

Richard Eckard receives funding from GRDC, Dairy Australia, Emissions Reduction Alberta, Agriculture Victoria and the Department of Agriculture and Water Resources.

The environmental impact of producing a loaf of bread has been analysed in depth - from the farm to the supermarket shelf.

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Rangers lost their lives in Kenya, Central African Republic, the Democratic Republic of the Congo and India

Eight wildlife rangers have lost their lives in four separate countries, in a week that highlighted the numerous hazards rangers face in protecting the world’s wild lands and species.

“It’s a tough week when we lose eight of our ranger family; some to poachers’ bullets and some to the other dangers that come with the territory,” said Sean Willmore, founder and director of the Thin Green Line Foundation, which supports widows and children of rangers killed in the line of duty.

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How worrying are the nitrogen dioxide levels at your child’s school?

Tens of thousands of children at more than 800 schools, nurseries and colleges in London are being exposed to illegal levels of air pollution that risk causing lifelong health problems.

The Guardian revealed on Friday that there are 802 educational institutions in the capital where pupils as young as three are being exposed to levels of nitrogen dioxide that are within 150 metres of nitrogen dioxide pollution levels that exceed the EU legal limit of 40µg/m3 (40 micrograms per cubic metre of air).

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As with all such lists, the 300 ‘scientists’ badly lack climate expertise

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If you read the headlines, it might have seemed impressive: “300 Scientists Tell Trump to Leave UN Climate Agreement.” Wow, 300 scientists. That’s a lot right? Actually, it’s a pitiful list.

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Council budgets for parks may have been cut, but you still love your local parks. We asked readers to share their pictures via Guardian Witness and here are some of our favourites.

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Fiskavaig, Skye This huge island is a complication of landscapes, and on its west coast you walk the divide between them all

The lady had drawn a map to direct me to the beach: there it was, easy enough, but where a road continued off the edge she’d inscribed an arrow, and the words “end of the world”. Curious, I follow the road off her map, past ancient rusting crofts on to a ribbon of singletrack, to where it stops. A knoll stands beyond a sheep gate and I climb it.

What I see from its knotty top is a place of transition. Beneath the knoll the land stops, falling to a sort of lagoon of strange, rumpled headlands and islands like pieces flayed off the land to drift. It seems this coast doesn’t want to commit to the ocean: here the waters of Lochs Harport and Bracadale coalesce into a strange enclosure of the Minch. Beyond, only South Uist’s taper offers harbour from the Atlantic’s ferocious north water.

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The Australian Heritage Council has called for comments on the heritage values of Centennial Park and whether it should be included in the National Heritage List. The period for comments closes on 28 April 2017.

The Australian Heritage Council is now assessing the place and has called for comments on its heritage values and whether it should remain in the National Heritage List. The period for comments closes on 28 April 2017

Get ready for heavier rain. Shutterstock

As the planet warms, rainfall and weather patterns will change. As temperatures rise, the amount of water in the atmosphere will increase. Some areas will become wetter, while others, like southern Australia, will likely be drier.

One measure of atmospheric moisture is called “precipitable water”. You may not have heard the term before, but will likely hear about it more often in the future. Both climate scientists and meteorologists are increasingly looking at it when studying weather charts.

There is a lot of uncertainty about future rainfall patterns, but there is one aspect that models have consistently emphasised — a larger proportion of rainfall will be heavy, even in some areas that are becoming drier. Atmospheric moisture is a part of this, and precipitable water is one measure of it.

So why do climate models project that we will get more heavy rainfall as the planet warms? At the heart of it is basic physics, which tells us that a warmer atmosphere can hold more water vapour than a cooler one — about 7% more for every 1℃ rise in temperature.

But meteorology will also play its part, and in the real world we have recently seen the sorts of weather systems that will drive heavier rainfall outside the tropics.

More tropical weather

A stream of very moist air from the tropics can often cause very heavy rain. These streams of moisture are sometimes called atmospheric rivers, but also have names such as the Pineapple Express in the United States or the Northwest Cloudbands here in Australia. An atmospheric river recently drenched California.

These sorts of tropical excursions happen naturally, but relatively infrequently. As the planet warms, however, regions like southern Australia and northern California can expect more tropical rainfall events, even as average rainfall declines.

Following the water

Like rainfall, precipitable water is measured in millimetres. It is derived by calculating how much liquid water you would end up with if you condensed all of the water vapour above your head — from Earth’s surface to the top of the atmosphere.

We calculate this using measurements from weather balloons, from satellite data, or from weather and climate models. The greatest amount of water vapour is generally near Earth’s surface, and it decreases with height.

Higher precipitable water values mean that more water is available for potential rainfall. We generally experience this as hot and humid weather. Just how much rain actually falls is dependent on the accompanying meteorological conditions. Under conditions favourable to thunderstorm activity, for example, high precipitable water translates into heavier rainfall.

Because it shows the location and movement of moisture, precipitable water is a great way for meteorologists to follow the movement of weather systems across the globe. In the animation above, it is easy to see tropical moisture streaming out from the equator toward the poles. Due to climate change, weather forecasters will increasingly be on the lookout for very high or record levels of precipitable water associated with those events.

In Australia, several heavy rainfall events in recent years have been associated with record-high levels of precipitable water. In late December 2016, heavy rainfall across central and southeast Australia was associated with record-high December precipitable water, with weather stations in Giles and Mount Gambier recording their highest values for any month. Heavy rains have continued over the western part of Australia through January 2017.

Earlier in 2016, record-high June precipitable water was also recorded at Sydney and Hobart, with Hobart recording a level on June 6 that was 38% higher than the previous record for that month. Both of these events involved tropical air laden with moisture sourced from record or near-record warm oceans, and drawn over southern Australia.

In both cases, heavy rainfall was widespread, with some record high daily rainfall totals.

Globally, as well as being the warmest year on record, 2016 broke records for global precipitable water in at least one international data set.

It should be noted that these record values are drawn from data covering just the period since 1992, as historical precipitable water values obtained using upper-air measurements of temperature and humidity are not easily comparable with present-day measurements. As such, precipitable water is more useful to weather forecasters than to climate scientists — although it becomes more useful as the length of the dataset increases, and can be used to evaluate model simulations.

The impact

The trend in precipitable water is expected to lead to an increase in the highest possible rainfall intensities and an increase in the frequency of extremely high daily rainfall totals, regardless of how average rainfall may change. A consequence of higher rainfall rates in a warmer world is increased flash flooding and also riverine flooding.

The implications of climate projections for heavier rainfall are many. In future, changes in the upper envelope of extreme rainfall may impact on the way we design things like urban water flows, buildings and flood mitigation. The fact that individual rainfall events can become heavier than the past in regions experiencing overall declines in rainfall and streamflow is an added nuance.

Beyond rainfall, higher moisture levels in the atmosphere also mean slower evaporation of sweat from the skin, making you feel hotter during particular heatwaves, and making evaporative air conditioning systems less effective. Just as changing temperatures influence decisions in areas such as planning, so too will increasing humidity and heavy rainfall events, even when they are episodic.

Karl Braganza is the Head of the Climate Monitoring Section in the Bureau of Meteorology's Environment and Research Division. Karl Braganza does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.

Acacia Pepler is completing a PhD with the ARC Centre of Excellence for Climate System Science, which is funded by the Australian Research Council.

David Jones does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.

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The crisis continues Although electricity consumption and pool prices fell sharply this week due to more moderate weather, 2018 base load futures rose another 5%. That’s three weeks in a row prices have risen 5%  and FY18 futures prices have now cracked the $100 MWh mark in all States ($99 MWh in Victoria). Prices in […]