Severe heatwaves show the need to adapt livestock management for climate



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Cows don’t do well in the heat.
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Elisabeth Vogel, University of Melbourne; Christin Meyer, Potsdam Institute for Climate Impact Research, and Richard Eckard, University of Melbourne

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. The Conversation


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.
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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, PhD Student, University of Melbourne; Christin Meyer, PhD student, Potsdam Institute for Climate Impact Research, and Richard Eckard, Professor & Director, Primary Industries Climate Challenges Centre, University of Melbourne

This article was originally published on The Conversation. Read the original article.

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Marine parks and fishery management: what’s the best way to protect fish?


Caleb Gardner, University of Tasmania

The federal government is considering changes to Australia’s marine reserves to implement a national system. This week The Conversation is looking at the science behind marine reserves and how to protect our oceans.


While academics often focus on biodiversity objectives for marine parks, the public and political debate tends to come down to one thing: fishing.

When former federal MP Rob Oakeshott cast one of the deciding votes in support of the Commonwealth marine parks plan in 2013, he explained that he believed they benefit fisheries. The federal government has also emphasised the benefit of marine parks to fisheries production.

There’s also an academic debate. When a study showed that the Great Barrier Reef marine park had harmed fisheries production, there was a passionate response from other experts. This is despite advocates arguing that reserves are primarily about biodiversity conservation, rather than fishing production.

Clearly, fishing is a hot issue for marine parks. So what does the science say?

How do marine parks protect fish?

The proposed benefits to fisheries from marine parks include: protection or insurance against overfishing; “spillover”, where larvae or juveniles from the parks move out and increase the overall production; habitat protection from damaging fishing gear; and managing the ecosystem effects of fishing such as resilience against climate change.

Marine parks regulate activities, mainly fishing, within a specified area. They come in a variety of categories. Some allow fishing, but the most contentious are “no-take” marine parks.

Fishery managers also sometimes close areas of the ocean to fishing. This is different to how no-take marine parks work in two ways: the legislative authority is different (being through fisheries rather than environmental legislation); and the closures usually target a specific fishery, whereas no-take marine parks usually ban all fishing.

Fishery closures, rather than no-take marine parks, are usually applied to protect special areas for particular fish, such as spawning sites or nursery areas. They are also used to protect habitats, such as in the case of trawl closures, which allow the use of other gear such as longlines in the same location.

Fisheries legislation bans damaging fishing gear outright, while benign gears are allowed. In contrast, no-take marine parks tend to exclude all gear types.

Displacing fishers

Neither marine parks nor fishery closures regulate the amount of catch and fishing effort. They only control the location. Commercial fishers take most fish caught in Commonwealth waters and most of this is limited by catch quotas.

When a no-take marine park closes an area to fishing, fishers and their catch are displaced into other areas of the ocean. This occurs for all types of fishing, including recreational fishing. Recreational fishers displaced by marine parks don’t stop fishing, they just fish somewhere else – and the same number of fishers are squeezed into a smaller space.

Marine parks increase the intensity of fishing impacts across the wider coast, which is an uncomfortable outcome for marine park advocates. Modelling of Victorian marine parks showed that displaced catch would harm lobster stocks and associated ecosystems, and was counterproductive to their fishery management objective of rebuilding stock.

Because ecosystems don’t respond in predictable ways, depletion of fish stocks from the fishing displaced from marine parks could lead to severe ecosystem outcomes.

For this reason, a second and separate management change is often needed after marine parks are declared, which is to reduce the number of fishers and fish caught to prevent risk of impacts from the park.

Controlling how many fish are caught (which is what traditional fisheries management does) has substantially more influence on overall fish abundance than controlling where fish are caught with parks, as shown recently on the Great Barrier Reef.

Public cost

Commonwealth fisheries catch quotas are routinely reduced if a fishery harms the sustainability of the marine environment. There’s no compensation to fishers, so there’s no cost to the public, other than a possible reduced supply of fish.

Catches can also be reduced to manage fishing displaced by marine reserves and the outcome is identical except in terms of the public cost. Creation of the Great Barrier Reef Marine Park led to over A$200 million in payments to displaced fishers. Another publicly funded package is planned for the Commonwealth marine reserves.

Marine parks also have high recurring public cost because boundaries need to be policed at sea. Catch quotas can be policed at the wharf, with compliance costs fully recovered from industry.

Do marine parks help fish and fishers?

Evidence of a benefit to fisheries from marine parks is scarce. However, there are some clear examples of fishing displacement that is so minor that there has been an overall increase in fish inside and outside the park.

These examples show that marine parks can sometimes benefit fish stocks, the fishery and also the overall marine ecosystem. However, these examples come from situations where traditional fishery management has not been applied to prevent overfishing.

This is consistent with modelling of marine parks that shows they only increase overall fish populations when there has been severe overfishing. This generally means that if there’s already effective traditional fisheries management, marine reserves cannot benefit fish stocks and fisheries, or restock fish outside the reserve (spillover) (see also here).

In jurisdictions where fisheries management is lacking, any regulation, including through marine reserves, is better than nothing. But this isn’t the situation with Australia’s Commonwealth fisheries where harvest strategies are used and overfishing has been eliminated.

The conclusions from modelling of marine reserves mean that the areas of the reserves that limit fishing would be expected to reduce fishery production and harm our ability to contribute to global food security.

The Coral Sea marine reserve, in particular, represents an area with known large stocks of fish, especially tuna, that could be harvested sustainably. Limiting fishing in the Coral Sea eliminates any potential for these resources to help feed Australians or contribute to global food supplies.

The potential sustainable, ecologically acceptable harvest from the Coral Sea is unknown, so we don’t know the full scale of what’s being lost and how much the recent changes reduce this problem, although Papua New Guinea sustainably harvests 150,000-300,000 tonnes of tuna in its part of the sea.

Allowing fishing doesn’t mean the oceans aren’t protected. Existing fisheries management is already obliged to ensure fishing doesn’t affect sustainability of the marine environment.

The Conversation

Caleb Gardner, Principal Research Fellow, Institute for Marine and Antarctic Studies, University of Tasmania

This article was originally published on The Conversation. Read the original article.