Australasian Science: Australia's authority on science since 1938

An Apple a Day Keeps the Drought Away

The fruit industry used 2.6% of water extracted from the Murray-Darling Basin.

The fruit industry used 2.6% of water extracted from the Murray-Darling Basin.

By Geoff Russell

Think twice the next time you see fruit trees portrayed in media reports about diminishing water allocations in the Murray–Darling Basin.

I imagine that most people have seen eco-footprint figures about the number of litres of water needed to produce a kilogram of this or that food. Or figures about how much energy is consumed during the production of meat, coffee, chocolate or rice.

Yet some significant aspects of the environmental footprints of different foods are rarely considered. A recent University of Queensland study has connected the current problems in the Murray–Darling Basin with the production of large per capita quantities of animal products.

Placing that research in context will take some time. Let’s begin with a quick quiz.

How many news reports have you seen about the water shortages in the Murray–Darling Basin without fruit trees being the dominant image? And how many of the 13,700 billion litres of water extracted annually from the Murray–Darling Basin go to fruit trees?

According to a 2004 CSIRO report, the fruit industry used 2.6% of water extracted from the Basin. The vegetable industry is even smaller at just 1.3%. The four biggest water users were dairy (34%), cotton (24%), rice (16%) and beef (7%).

But there is always another report. The Guide to the Basin Plan has foreshadowed a reduction of about 4000 billion litres of water extracted from the Basin. While this has been greeted with outrage, it would only roll back water use to about 1995 levels.

Allocation Increases Since 1995
The rollback to 1995 levels is no accident. Indeed it was the post-1995 expansion of water use that made just such a rollback inevitable.

Between 1995 and 2000 there was a huge expansion in water use in the Basin, starting at 9,300 billion litres and rising to 12,000 billion litres. The current figure used in the Guide is higher still at 13,700 billion litres, but there is no information about who is getting it.

The 2004 CSIRO report gives us clues. Some 1,700 of the 2,700 billion litre increase during the late 1990s was for the dairy industry, a further 700 billion litres was for cotton, with rice and grapes picking up the crumbs with a couple of hundred billion each.

By 2000–01, dairy was using nine times more water than fruit and vegetables combined. Dairy’s increase brought its total water use to 4,200 billion litres, while the fruit industry got a 67 billion litre increase to bring its total to 310 billion litres.

Now that the excrement is flying off the fan, everybody in the Basin will be paying a penalty for the unsustainable expansion of the dairy and cotton industries during the late 1990s. Even when the dry times hit, cotton and rice farmers stopped planting but dairy farmers continued sucking at the rivers with giant pipes until more than a few sold up, destocked or went broke. The Guide talks of increased dairy farmer debt, and the national dairy herd has declined by about 10% since the heady days of 2000–1.

Regional Climate Shift
It is now 2011, and the hottest decade on record in Australia has ended. But last year’s wet winter, spring’s floods and media talk of a broken drought should lead everybody to ask whether the weather has returned to “normal” or whether we have moved to a drier climate in which recent months were abnormally wet.

The Guide lists the maximum inflow to the Basin’s rivers as 117,907 billion litres in 1956, with a minimum of just 6,740 billion litres in 2006. The past 15 years have seen the lowest flows in more than 100 years of record-keeping at Wentworth near Mildura, with an average during the past decade that is well below the long-term average.

The change in Australia’s climate, particularly in the regions we care about, is well-documented. Droughts aren’t so much drier as hotter, with both maximum and minimum temperatures rising by a full degree over the past 60 years.

So while the droughts of 1982, 1994 and 2002 have had similar rainfall in total, the evaporation has been increasing so that less water runs into the rivers of the Basin.

Global and Local Causes
There are two kinds of contributing causes to our changing climate that we know about.

The global causes relate to the extra heat that has been warming the oceans and reducing the amount of sea-ice. The sea-ice is important because it reflects large amounts of heat. Lose the ice and that heat warms up the ocean.

A more immediate influence on the climate is how humans change the landscape. In Australia there are less than 2 million hectares of urban areas dotted within 770 million hectares. Cities aren’t the issue, but the deforestation to feed their populations is a boomerang that returns to wallop us twice. It not only puts carbon dioxide and trace gases like methane and nitrous oxide into the atmosphere, it also has more immediate climate impacts.

How Does Land Clearing Change the Regional Climate?
The mechanisms by which deforestation changes climate have been understood at a qualitative level for decades, but measuring the crucial variables properly has had to wait for good satellite data. When you change the amount and type of vegetation cover in an area you have an impact on both evaporation and transpiration.

Here’s a little experiment you can try to show how big an impact that vegetation changes can have. Fill two containers with soil and wet them both with the same amount of water. Get them good and soggy. Cover one container with 30–50 cm of mulch. It doesn’t matter how much you add, but the more you add, the bigger the impact you’ll see.

Now place the containers out in the sun. Weigh them from time to time and watch the weight change during the day as the soil dries out. When a friend of mine did this during a soil science course, the mulched container lost 4.5 g/hr while the unmulched container lost 28.2 g/hr. Use your imagination to scale up this effect.

So how can you measure vegetation and water flows in an area? Drive around in a ute counting leaves and measuring puddles? No, but satellites can now measure green-ness and other necessary details accurately enough to do the job and determine the impacts that reduced vegetation cover is having on regional climates.

Quantifying the Changes
In a remarkable study published in 2009, Ravinesh Deo and colleagues at the University of Queensland and the National Center for Atmospheric Research in the USA examined whether land cover change in Australia could have had a significant impact on regional climate.

Using a CSIRO climate model, they plugged in sea surface temperature and sea-ice history between 1951 and 2003 together with vegetation patterns. This allowed them to see what would have happened if Australia had been surrounded by the same ocean temperatures but with the land cover still as it was 200 years ago.

What they found was that we wouldn’t have had as much warming if the forest cover had remained as it was 200 years ago. They concluded that land cover change “has exacerbated climate extremes in eastern Australia, thus resulting in longer-lasting and more severe droughts”.

It isn’t only global warming that is changing our climate. It is the removal of our forests and woodlands.

How Much Land Have We Cleared, and Why?
The 2006 State of the Environment report estimates that Australians have cleared about 100 million hectares since white arrival. This is a net clearing figure. The official land use data from the Bureau of Rural Sciences is given in Table 1. Combining the two sources of data reveals who has been clearing land. Urban areas and cropping take up 25.3 million hectares. The other 70-plus million hectares has been cleared for sheep and cattle.

The causes of the Murray–Darling Basin’s predicament are threefold:

• climate change is a major driver at the global level, and we all must take some responsibility for this;

• deforestation has been a major driver at the regional scale, and this is due to demand by meat and wool consumers; and

• the main driver in the short term has been dairy with a little assistance from cotton.

The drivers of the Murray–Darling Basin problems are, for the most part, the extensive livestock industries rather than cattle feedlots or pig and chicken factory farms. Nevertheless the latter drive land clearing for feed cropping, outbid the world’s undernourished humans for food and typically consume five times more of our grain production than we do.

Those who think we have some kind of environmentally benign meat production system only have to look at the history of our extensive livestock industries. In addition to driving regional climate shifts they have driven the majority of species extinctions.

Rice-growing in Australia is frequently subjected to tirades without cost–benefit comparisons. Rice’s water use in the Murray–Darling Basin is small compared with dairy, and the food value of the
1.6 million tonnes of rice produced from 177,000 hectares during the industry’s peak in 2000–01 far exceeds the food value of the 2.5 million tonnes of cattle and sheep carcases produced from 440 million hectares under grazing. We have been a net importer of rice for a few years now, with an import excess of 130,000 tonnes in 2009–10.

The stress to the Murray–Darling Basin is a significant part of the eco-footprint of the meat and dairy industries that isn’t captured in the usual eco-footprint studies.

Geoff Russell is a member of Animal Liberation and author of CSIRO Perfidy, in which he argues that The CSIRO Total Wellbeing Diet is the most environmentally destructive diet on the planet. This article is a reworking of a piece originally published on bravenewclimate.com.