Climate change

October 27, 2010

Who crippled the Murray Darling Basin?

Filed under: Climate Change, Water Resources — buildeco @ 11:32 pm

Guest Post by Geoff  Russell.

Geoff is a mathematician and computer programmer and is a member of Animal Liberation SA. His recently published book is CSIRO Perfidy.

If I see another fruit tree, I’ll throw up!

I guess that most people have seen information about the eco-footprint of different foods. It takes so many litres of water to produce a kilo of this or that food. Or figures about how much energy is consumed in the production of meat, coffee, chocolate or rice. But there are much bigger aspects to the environmental footprints of animal product that are rarely considered in such studies. This blog piece will end up at a great piece of Australian scientific research from the University of Queensland (with software from CSIRO) on the big picture impacts, the regional impacts of choosing to eat large amounts of animal products.

Placing that research in context will take some time, but before we get started on these big issues, let’s have a quick quiz.

  1. How many news reports have you seen about the water shortages in the Murray Darling Basin (MDB) without fruit trees being the dominant image? Rows of citrus fill the frame like Matt Preston’s gourmet gut. I guess it’s more convenient for TV film crews than battling the high seas of manure at a dairy.
  2. How many of the 13,700 billion litres of water extracted from the waters of the Murray Darling Basin go to fruit trees?

The fruit industry, according to a 2004 CSIRO report used 2.6 percent of water extracted in the basin. The vegetable industry is even smaller at about half that … 1.3 percent. The four biggest users were, in order, dairy (34 percent), cotton (24 percent) and rice (16 percent) and beef (7 percent).

You could cynically argue that it is quite accurate to feature fruit trees in the MDB stories. The fruit growers may be the smallest in the list of people causing the problems in the MDB, but they will, individually, be paying a major price.

Now let’s slow down, take a step back and look at the bigger picture behind the MDB problems.

Global warming “gone” … but the Murray crisis continues

Global warming has largely vanished from center stage in Australian political life. The old Prime Minister was too poll-driven to take tough decisions and the new one is transparently disinterested in such matters.  The boredom in her voice even overwhelms the dry monotone delivery and becomes palpable as she goes through the motions of feigning Government commitment to de-carbonising our lifestyles.

So concern over global warming has cooled precisely as its impacts in the Murray Darling Basin conspire with greed and stupidity to cause a problem that will be evident in foreclosures, suicide and despair in coming years. But we have a new report. There is always another report. This one is 260 pages of detail called “Guide to the Basin Plan”. It is floating a reduction of about 4,000 billion litres in water extractions from the basin. This would roll back total water use to about 1995 levels (as estimated on page 73 of this 2004 CSIRO report … pdf).

Post 1995 expansion … placing the straw on the camel’s back

It won’t take much longer before we get to the science that shows that land clearing impacted the regional climate and prepared the MDB system of water allocations for failure. But in the short term, it was expansion of the dairy industry in the late 1990s that made the current retraction in water use in the Murray Darling Basin inevitable.

Between 1995 and 2000, there was a huge expansion in water extraction in the basin starting at a baseline of 9,300 billion litres and rising to 12,000 billion litres. The current figure is a little higher at 13,700 billion. Some 1,700 of that 2,700 billion litre increase was for the dairy industry, and about 700 billion extra for cotton with rice and grapes picking up a couple of hundred billion each. By 2000/1 the dairy industry was using about 9 times more water than fruit and vegetables combined.

Let me repeat. The dairy industry got a 1,700 billion litre increase, bringing its total water use to 4,200 billion litres, while the fruit industry got a 67 billion litre increase to bring its total to just 310 billion litres.

Now everybody pays

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

I remember seeing an Advertiser story about the Murray with a dairy farmer standing next to his water sucking pipe and looked down at the river far below. The picture was taken to drive your focus to the low level of the river, but all I could think about was what a huge mother of a pipe!

The bigger picture behind the regional climate shift

It is now 2010 and the end of the hottest decade on record in Australia. But the wet winter, the floods and media talk of breaking droughts should lead everybody to ask whether the weather has returned to “normal” or whether we have moved to a new drier climate normal in which this winter is actually abnormally wet. The Guide to the Basin report lists the maximum inflow to the basin’s rivers as 117,907 billion litres in 1956 and the minimum of just 6,740 billion litres in 2006. The last 15 years have seen the lowest flows in over 100 years of record keeping at Wentworth near Mildura with an average during the past decade well below that of the long term average.

The change in climate in Australia, 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 causes and local causes

So we know what is happening … the climate is changing. The important questions are why and what can we do about it.

There are two kinds of contributing causes that we know about.

  1. The long range causes relate to the extra heat that has been warming the oceans and reducing sea ice. The sea ice is important because it reflects large amounts of heat. Lose the ice and that heat warms up the ocean. You can estimate some critical climate variables by thinking of the earth as a huge sphere and just count the proportion of the sphere that is ice covered and therefore highly reflective. The estimates using this crude modelling can be quite close to highly complex modern methods done with supercomputers.
  2. A more imediate influence on the climate is how humans change the landscape. This is a boomerang that returns to wallop us twice. Deforestation not only puts carbon dioxide and trace gases like methane and nitrous oxide into the atmosphere, it also has more immediate impacts.Appreciating the difference being in full sun and under a shady tree takes us all some way to an appreciation of deforestation’s impacts. Climate change sceptics are fond of trying to use the urban heat island effect to support claims that the climate isn’t really changing. They say that the apparent rise in temperature is because too many thermometers are too close to big built up areas. There is indeed such an effect. It has been understood for a long time. In Australia there are less that 2 million hectares of urban areas dotted in a land mass of 770 million hectares. The urban heat island impact is modest and localised. What isn’t at all modest or localised is the impact of massive deforestation during the last hundred or so years.

A number of Australian scientists have looked at the impact of deforestation on climate. The mechanisms by which deforestation changes things have been understood quite well understood at a qualitative level for decades but measuring the crucial variables properly has had to wait for good satellite data which has recently enabled solid results.

How does land clearing change the regional climate?

When you shine the sun’s rays on something with a mirror, it heats up. When you shine the sun’s rays on water it not only heats up, but some of it evaporates. Now what happens when you perspire? Perspiration is just evaporating sweat and it makes you feel cooler. This is because it takes a little extra energy to turn the water into a gas and that extra heat comes from your body. When plants sweat, it is called transpiration and it cools the plant, just like us. The details are different, but the impacts are similar. 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 do at home to drive home how big an impact that vegetation changes can have. Fill two containers with soil and then 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 exactly how much you add, but the more you add, the bigger 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 grams per hour of water and the unmulched container lost 28.2 grams per hour. Wow!

Vegetation works like mulch in shading an area, but if it is growing, it will transpire water. Transpiration and evaporation are often talked about together and called evapotranspiration. The two mechanisms add together to determine water loss in an area. A related mechanism occurs when there is plenty of water in an area. More of the sun’s energy ends up evaporating that water rather than making the area hotter.

So how can you measure and accurately calculate vegetation and water cover in an area? Drive around in a ute counting leaves and measuring puddles? That would be impossible. But satellites can now measure green-ness and other necessary details accurately enough to do the job and determine the impacts which vegetation change is having on the regional climate.

Quantifying the changes

So at last we come to the remarkable study published last year in a top scientific journal by Ravinesh Deo and colleagues at the University of Queensland (UQ) and the National Center for Atmospheric Research (NCAR) in the US. They looked at the satellite data, worked out the details and, were able to put some tentative numbers to all this. Sometimes with modelling like this, you may qualitatively have a strong idea of what is happening but when you put numbers on things you find that the result is negligable. This shows your intuition is deficient. In this case, the modelling gave numbers that are close to those that are being actually measured on the ground so we can be fairly sure that the modelling is reasonable. The paper didn’t look at the South West in Western Australia, but I’d be guessing the results would have been similar.

Here’s a rough explanation of what they did. They used a CSIRO climate model (Mark 3) (link is pdf download). The input was the sea surface temperature and sea ice history between 1951 and 2003. The output from the model is the climate. Their use of the model 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.

Put simply, we wouldn’t have had as much warming with the forest cover of 200 years ago. 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?

A fuller account of this deforestation will need another blog piece, but for now a simple table of land use data will reveal the deforestation drivers. Here’s some official figures from the Bureau of Rural Sciences

Land Use Category Million Hectares
Urban Intensive 1.4
Rural residential 0.9
Cropping 23.0
Irrigated pastures and crops 2.5
Grazing native vegetation 419.4
Mining 0.1
Plantation Forestry 1.6
Forestry 13.3

Australian have cleared about 100 million hectares since white arrival. This is a net clearing figure. Add up the urban areas and the cropping and we come to 25.3 million hectares. Almost all other land clearing has been to run sheep and cattle.

So the causes of the Murray Darling Basin predicament are 3 fold:

  1. In the long term, climate change is the ultimate driver and we all have a responsibility here.
  2. In the medium term, deforestation has been and will continue to be a major driver and this is down to meat and wool consumers.
  3. In the short term, the main driver has been dairy with a little assistance from cotton.

Note that the drivers of the MDB problems are, for the most part, the extensive livestock industries. They are not, in particular, the factory farm industries. Factory farms drive land clearing for feed cropping but this is relatively small compared to land clearing for extensive livestock production. The muddle headed romantics who think there is some kind of environmentally benign meat production system only have to look at the results of our extensive livestock industries in Australia. They have driven the majority of species extinctions, and underly the regional climate shifts causing so much of the pain and suffering (human and non-human) in rural Australia.


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