Carbon Farming Knowledge

Ag on target to lead greenhouse emissions

CLIMATE change will have significant impacts on how farming is conducted by 2050, according to agricultural scientist Professor EWR ‘Snow’ Barlow.

Resolving “grand scientific challenges” associated with crop response to elevated carbon dioxide levels and reduced nitrogen uptake efficiency might take 15 to 20 years, but agriculture will also come under social pressure to clean up its performance, Professor Barlow predicted.

By 2050, agriculture may well be Australia’s equal top greenhouse gas-emitting industry – equal to the power generation industry – and responsible for most of the nation’s methane and nitrous oxide emissions, he said.

Along with carbon dioxide, methane and nitrous oxide are acknowledged as “drivers of climate change”.

Professor Barlow suggested assisting agriculture to adapt to maintain its “social licence” to operate in a changing environment could be as great a challenge as maintaining nutrition and quality in the food it produces.

He is the foundation professor of Horticulture and Viticulture at the University of Melbourne and his research focuses on physiological responses of plants to environmental stress, including climate change.

A member of several government and agriculture industry climate variability assessment advisory groups, this month Professor Barlow presented the Hector and Andrew Stewart Memorial Lecture to a full house at The University of Western Australia (UWA) on agricultural challenges of climate change.

WA was “no stranger” to climate change and Perth was the first Australian city to recognise its impact in that it was running out of water and needed a desalination plant to supplement supply, he said.

“Now you’ve got two (desalination plants),” he said.

Professor Barlow said while Bureau of Meteorology (BOM) climate reports indicated Australia generally was one degree Celsius hotter than it was 100 years ago, across its Wheatbelts the increase was “more like 1.5 degrees” and in WA there were “pockets where the warming is really 1.5-2 degrees”.

But it was the changing frequency in extreme weather events that are likely to have most impact on agriculture.

“In agriculture, the things that bring you undone are not the one degree on the top of monthly maximum temperatures, they’re actually the heat waves,” he said.

BOM data showed increasing probability of more months with extended periods of daytime temperatures above 35-38 degrees.

“Essentially, monthly very hot daytime temperatures occurred approximately 2.2 per cent of the time over the period 1951-1980, 6.5pc of the time over the period 1981-2010 and 11.45pc of the time 2001-2015.

“Over the same period, the frequency of very cool monthly minimum night time temperatures declined by about one third.

“That’s important for crops and it’s also important for animals,” he said.

BOM and Australian Export Grains Innovation Centre research indicated rainfall patterns were changing, with much of southern Australia not only drier but transitioning away from a predominantly winter rainfall pattern to a summer dominant rainfall pattern over the past 20 years.

In WA this had compressed the area of the Wheatbelt receiving predominantly winter rains into the western half and made rainfall more variable in the eastern half.

Professor Barlow said changes had been most pronounced in the past 15 years but so far science and uptake of new technology by farmers had been able to maintain actual wheat yields.

But the CSIRO had calculated potential yield averages had declined from 4.4 tonnes per hectare to 3.3t/ha – a 28pc reduction due mainly to rainfall changes, which was worrying, he said.

“The good thing about the performance of Australian wheat farmers so far is (while) they might not support climate change, they might not believe it is happening, but they are adapting,” Professor Barlow said.

Modelling of pasture production in northern Victoria and grape growing in the Coonawarra region of South Australia had shown impacts of climate change as a “compression” of growth and harvest periods.

This had “cost implications” for agriculture, with more infrastructure required to handle narrower optimal planting and harvest windows, but then remaining idle for longer periods.

Dairy industry studies showed milk production slumps due to more frequent “heat waves” had a lingering effect on production for the rest of the season.

Current levels of research showed climate change impacts on agriculture were sometimes inconsistent and not uniform, so much more detail work was required through collaboration between farm sector, agribusiness and universities, he said.

Professor Barlow reminded those at the lecture “no matter how good the science is, you won’t get anywhere if you don’t have the industry on side and engaged in what you want to do”.

“There are some underlying fundamental scientific challenges in climate change that I don’t believe we are really engaging in as yet, and these will have a longer time frame to solve and therefore you have got to be underway earlier and you have got to be funded earlier,” he said.

Professor Barlow said the primary challenge was how agriculture coped with the dual responsibilities of cutting emissions and increasing production.

Australia’s greenhouse gas emissions profile was “not dissimilar” to the global situation with power stations and power generation responsible for 59.8pc of greenhouse gases, transport 17.7pc, agriculture 13.8pc and industry 6.2pc.

“Fundamentally, what the future of Australia and New Zealand’s greenhouse gases comes down to is energy and agriculture,” Professor Barlow said, pointing to targets of 50pc reduced greenhouse gas emissions by 2050.

“Where’s that (reduction) going to come from?

“Primarily decarbonising of the energy sector through renewables – that’s the only place, outside of agriculture of course, that it can come from.”

Professor Barlow said at the same time State departments of agriculture had objectives to double agriculture output and, while they might not meet their objectives, they could go close.

“But if you did that, doubled our agriculture production and everything else stays the same, then the greenhouse gas emissions attributable to agriculture becomes about a quarter of all emissions – about 28pc rather than about 14pc.

“If the energy sector’s emissions are halved to 30pc and agriculture production is doubled, suddenly agriculture’s share of greenhouse gas emissions has jumped to half.

“Is other industry, like mining, going to be happy decarbonising when agriculture doesn’t?

“There will be pressure from other industries, and there will be pressure from the electorate in general, for agriculture to explain how it is going to decrease its emissions.

“Our current Prime Minister (Malcolm Turnbull) was the champion of a thing called the Carbon Pollution Reduction Scheme in 2007 which was (then Prime Minister) John Howard’s proposal to do something about climate change – it was an emissions reduction scheme.

“In that scheme agriculture was included, it was actually signalled to become part of this Carbon Pollution Reduction Scheme by 2015.

“So it’s not as though it hasn’t been on the agenda before.

“When we start to look at global challenges one of them is agriculture needs to address some of the fundamental science underneath it that results in these greenhouse gas emissions,” Professor Barlow said.

Nitrous oxide and methane were agriculture’s main contribution to greenhouse gases and “on most occasions” addressing them was a “win-win situation”, he said.

“If you decrease greenhouse gas emissions you’ll probably see either an increase in productivity or a decrease in costs because you’ll invest less money in fertiliser, or see greater animal growth.”

Professor Barlow said significantly increased nitrogen fertiliser use by Australian farmers since 1960 – based on application rates they are now one of the world’s highest users – was behind agriculture’s nitrous oxide emissions.

He said apart from adding to greenhouse gases, nitrogen also had “off-site” consequences.

It could transform into ammonia, evident in depositions around intensive animal feed lots, or excessive use could lead to water pollution and green lakes and waterways.

Adding to the problem was evidence nitrogen fertiliser was diminishing in efficiency with higher application rates required to maintain response.

Professor Barlow said there was early evidence from Victorian tests of reduced nitrogen content in cereal crops and rice grown in an elevated carbon dioxide environment, which had implications for plant protein levels.

“What we think the plant is doing is taking up less nitrogen because it can use its machinery more efficiently (in an elevated carbon dioxide environment) and therefore doesn’t have as much RuBisCo (an enzyme that helps combine carbon dioxide with sugar during photosynthesis and makes up about half of the protein in a leaf),” he said.

“Nitrogen is so vital because it is a major component of chlorophyll, the compound by which plants use sunlight energy to produce sugars from water and carbon dioxide.

“It is also a major component of amino acids, the building blocks of proteins.”

Early research had shown a 10-15pc reduced nitrogen uptake in wheat and rice grown in elevated carbon dioxide levels, but legumes like field peas and soybeans, as well as maize, showed no change, he said.

“The world’s cereals provide probably half the protein our global population eats.

“If you decrease the amount of protein in cereals you decrease the diet of a lot of people.”

Professor Barlow said apart from nutritional changes with higher carbon dioxide levels, tests had also indicated changes to the baking quality of some wheat varieties, but not all varieties had been tested and results were not conclusive.

There was also evidence from United States of America sampling of forage crops over the past 20 years that plant zinc and iron levels also decreased with higher carbon dioxide.

Elevated carbon dioxide levels was an established consequence of climate change, he said, with atmospheric carbon dioxide increasing from just over 300 parts per million (PPM) in the 1950s to 400ppm now and projected to reach 550ppm by 2050.

The broad impact of elevated carbon dioxide levels had long been known with horticulture enriching carbon dioxide in commercial greenhouses to promote growth, but much more detailed research on its impact on nutrition, quality and genetic variability was required, Professor Barlow said.

“It is one of the most fundamental things in plant sciences, how we understand the response of plants to elevated carbon dioxide and because of its implications for quality and growth, I think we’ve got to do a lot more work on that.”

Early research had also started on reducing methane emissions – agriculture was responsible for 52pc of methane emissions, he said.

“We know ruminant animals probably lose 20pc of their energy through methane in their production cycle.

“We know that through feed supplements we can probably get that down to about 15-18pc if we’re lucky.

“Of course that depends on them being captive animals, you can’t feed these supplements to free-range animals which most of Australia’s beef industry are.

“There are some genetic approaches that are showing some action and there is some basic work in identifying some of the pathways that could be helpful.

“We have a proud history of agriculture research in Australia.

“If we are going to do something about these grand agricultural challenges that underlie our response to climate change, we are going to have to marshal a big research effort (and) it is probably going to have to come predominantly from the university sector,” Professor Barlow concluded.

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