Sunday, February 20, 2011

What's so special about NSF?

I found an interesting blog entry by Willem Vervoort, Associate Professor Hydrology and Catchment Management at the Faculty of Agriculture, Food and Natural Resources at the University of Sydney, he concludes:

So the core of Peter's ideas are embedded in existing and well established ideas about biological farming and about water harvesting. They are not controversial to me. It will work as long as you have low salinity soils, low salinity input water and a relatively flat landscape and you are close to a water source. It also will work better in grazing systems as the nutrient loss can be managed better. Wheat and other cropping systems would really have to think hard about rotations and carbon balances.

All the rest of the ideas from Peter are only layering around this core and some of it I really cannot see any use for, or I find a bit silly.

Saturday, February 12, 2011

Fun with numbers!

I was having some fun over at The Land the other week with one of the denizens claiming undersea volcanoes are responsible for the melting of the Arctic ice cap. While he wanted to rant about conspiracies and all that he does raise an interesting point which has made me think, just how much heat (and of course energy) do volcanoes need to add to the oceans to actually make any difference? So I figured I might do some calculations, there are a number of assumptions I will make and I’ll be quite open about them, I will however be generally erring on the conservative side.

It’s going to get a little complex but none of the calculations are all that difficult, grab a bit of paper and a pen.

We’ll assume a rise in average ocean temperature of 1 degree over 100years, assuming that this is constant throughout the water column (if it were due to volcanic activity the difference would be higher the lower you go as that’s where the heat source is but to make it easy I’ll stick with a one degree warming throughout the column), so how much energy does this take?

From basic physics we know that it takes 4.2 Joules of energy to raise the temperature of one gram of water by one degree Celsius (I’m assuming fresh water, I do know it’s salt water but the difference in the end will only be minor), from a quick Google search ( we find that the worlds ocean volume is around 1.3-1.4 billion cubic kilometres.

Assuming one gram of water equals one millilitre (yes, I do know the density will be a little different with salt water but in the end it really won’t make much difference), one cubic metre will equal one million millilitres (1 x 106 ml) , one cubic kilometre will equal one million billion millilitres (1x 1015 ml) and will require 4.2 x 1015 Joules to warm it by one degree, so the whole ocean will require 4.2 x 1015 x 1.3 x 109 or 5.46 x 1024 Joules of energy to raise it by one degree (this does make a very, very big assumption that there’s no energy lost from the system, counting in energy loss this figure would be much higher).

That’s a lot of joules, so what does this equate to? Another Google search on “world energy consumption” tells us the average annual energy consumption is roughly 5 x 1020 Joules (my search said 4.74 x 1020 but I rounded it up just for ease of calculation) so dividing or 5.46 x 1024 by 5 x 1020 gives us 10920 years of the worlds energy use would raise our oceans by 1 degree Celsius.
So what? I hear you quite rightly say, “the energy comes from cooling magma not from burning coal” so what we need to know are the melting point of magma and the specific heat capacity (specific heat capacity is how much energy it takes to raise one gram of a substance by one degree Celsius).

Another Google search on “magma melting temperature” gives an answer of between 700 and 1300 degrees to melt it depending on the makeup of the magma, in this case for ease of calculation we’ll pick a mid point of 1000 degrees. As for specific heat capacity, granite has a specific heat capacity of 790J/kg/degree or 0.79J/g/degree (we’ll round it up to 0.8J/g/degree for easier calculations, don’t worry this works out as more heat released for less weight which helps out the conservative nature of the calculations).

Time for a breather? Just to reiterate, we’ve figured out how much energy it would take to warm the world’s oceans by one degree Celsius, what we’re doing now is figuring out how much volcanic magma we would need to heat it by that much, as I’ve said, I’ve made a number of assumptions but they should result in a fairly conservative answer.

Ok, the amount of energy going into melting something should be the same as that released when it solidifies and cools so to raise 1 gram of granite to melting point of around 1000 degrees from a starting temperature of 50 degrees (it’s a lot hotter at the bottom of the oceanic crust than it is at the top so I figured 50 degrees would be a reasonable average), would require 950 (the temperature difference) multiplied by 0.8 (the specific heat capacity) or 760 Joules, that would also be released as it cools and solidifies.

So, what does that mean? Fair question, how many tonnes of magma would need to cool from 1000 degrees to 50 degrees to release that sort of energy?

Taking our 5.46 x 1024 Joules of energy needed divided by 760 gives us 7.2 x 1021 grams or 7.2 x 1015 Tonnes. Granite has a density of around 2.7T/m3 and basalt around 3T/m3, for ease of calculations I’ll go with the basalt density which gives 2.4 x 1015 cubic metres or 2.4 million cubic kilometres of magma needing to be produced by the worlds mid ocean ridges, volcanoes etc over 100 years to raise the oceans temperatures by 1 degree celcius (remember I’m assuming no loss, the actual number would be much higher).

As this mostly happens in the oceans and the oceanic crust is between 7 and 10km thick, we’ll assume a thickness of 10km giving 240 000 square kilometres of oceanic crust formed in 100 years.
Actually, it isn’t, that assumes all the action happens at the mid ocean ridges where the crust is formed and nothing at the subduction zones so I’ll halve it assuming (quite reasonably I think) that there’s as much energy released at the subduction zone as at the mid ocean ridges, so we’re looking for 120 000 square kilometres of new ocean crust formed in 100 years (remember, this is a conservative estimate, the actual number would be much more). Again using Google there’s around 80 000km of mid ocean ridge which means they’d have to widen by 1.5km in a century, or again being nice 750 metres either side meaning the continents would have to move at least 7.5 metres a year this is around 150 times faster than they are currently moving and to move 150 times faster you’d need 22 500 times the energy (remembering basic physics F=MV2).

These figures are very much in the lower end of the ballpark so if there is an influence from oceanic volcanoes on sea temperature and climate change we can see that it is very, very little.

Mr Toad will not be happy.

Willow species (Salix spp) with the exception of Weeping Willow, Pussy Willow and Sterile Pussy Willow (Salix babylonica, S.calodendron and S.x. reichardtiji) have been listed as one of twenty one Weeds of National Significance, these weeds have been listed due to:

the invasiveness of a weed species
a weed's impacts
the potential for spread of a weed
socio-economic and environmental values.

and are regarded as being a major threat to the Australian environment. In the cae of the Willow it has been listed because
Most species of Willow are Weeds of National Significance. They are among the worst weeds in Australia because of their invasiveness, potential for spread, and economic and environmental impacts. They have invaded riverbanks and wetlands in temperate Australia, occupying thousands of kilometres of streams and numerous wetland areas (CRC 2003).

Willows spread their roots into the bed of a watercourse, slowing the flow of water and reducing aeration. They form thickets which divert water outside the main watercourse or channel, causing flooding and erosion where the creek banks are vulnerable. Willow leaves create a flush of organic matter when they drop in autumn, reducing water quality and available oxygen, and directly threatening aquatic plants and animals. This, together with the amount of water willows use, damages stream health (CRC 2003).

The replacement of native vegetation (e.g. river red gums) by willows reduces habitat (e.g. nesting hollows, snags) for both land and aquatic animals (CRC 2003).

Willows have only invaded about 5% of their potential geographic range in temperate Australia (CRC 2003).

Tasfish has quite a good article on it. So you'd think that given the threat to the ecosystem that people wouldn't be promoting it's use? You'd think so but Natural Sequence Farming has been and is continuing to promote the planting of willows, even claiming they are the worlds number one riparian plant (whatever that means)!

Given that the results of the ARC Barramul Project were released last year and accoding to their website

proved Peter's NSF processes are what he has been saying all these years
you'd think the report would back them up. Well what does the report have to say?

* Casuarina cunninghamiana accelerates bench development and plays a synergistic role in channel contraction (P7)

* Clonal grasses, reeds and tree C. cunninghamiana assisted geomorpic processes.
* River training works were effective after 1981 because they coincided with the main period of natural channel contraction.
* Baramul NSF stream works assisted vegetation recovery but occurred after the main period of channel contraction. (P21)

* Significant positive feedback between C. cunninghamiana recruitment and the rate of channel contraction after extensive channel widening. (P23)

* The recolonisation of native vegetation such as Casuarina cunninghamiana (given appropriate seed source) plays an important and synergistic role in channel contraction, negating the use of such weeds as Salix spp in NSF (P44)

Native plants such as river oak (Casuarina spp) have proven extremely effective at stabilising stream beds and banks. Stock exclusion and limited grazing enhanced the establishment of native seedlings. The use of natives for this purpose is preferred over exotic weeds. (P48)

Well, nothing at all really, it gives a great wrap to Casuarinas and very little on willows. Mind you this all could be quite academic in a couple of years anyway as this year has been a fantastic year for the spread of the Willow Saw Fly, which now appears to be in a significant number of rivers and creeks in the Hunter Valley and in some areas causing significant damage (sorry, my camera batteries were flat but I'll get back out and get a few shots).

And see my previous post on weeds.