Tuesday, September 15, 2009

Livestock in Riparian Zones - Reality vs Greenspin

How a picture can tell a thousand lies.

A green blogger recently provided a link to a NSW Catchment Management Authority web site as “evidence” of the degraded condition of “our” environment due to grazing of stock in riparian zones. But in reality, the site provides a very good example of how a few pictures and sloppy captioning can tell a thousand lies. See;
http://www.cw.cma.nsw.gov.au/pdf/Information/BMPs/CWCMA_Information_BMP_0288_ripariansheet_livestockmanagement.pdf
The introductory text said;
“Inappropriate livestock grazing is one of the most significant causes of degradation to the land-water interface in Australia. Livestock have long been part of the Australian landscape. Cattle, sheep, horses, goats and pigs arrived with the first settlers in the 1780s and moved with them across NSW into the Central West. Settlements sprang up along river systems supported by clean water and fertile floodplain soils. Since that time, livestock have caused damage to the most sensitive part of the landscape – our riparian lands.”

This picture was captioned;
"The access of livestock to waterways has many detrimental impacts on riverbank stability and water quality. (NSW DPI)"

True, we see cattle by a creek and some exposed soil which would lead most urban punters to conclude that this picture is representative of the entire length of the creek on that farm and representative of all grazed creek banks on all farms.

But we can be quite certain, given the proven MO of CMA’s and their staff, that the picture shows worse than average impacts. A random inspection of the first, second and third order farm streams that account for most of the riparian interface in the landscape is unlikely to provide a single example of conditions like those shown. It is also highly improbable that anything like those conditions would be replicated over the entire length of that particular stream. Indeed, there may be only one or two such examples on the entire property.

It is also quite certain that the conditions produced in the photo represent the sum of all cattle damage over a period of more than 100 years. Once the landform modification has been made by the stock to match their normal level of traffic, the rate of change (called degradation) will reduce to a minimum. Most of the modification shown in the photo would have been done in the first decade after settlement.

Stock can produce physical modifications to a small portion of a riparian zone when they are first introduced to a landscape or when a major increase in animal traffic at a particular point takes place. If the stocking rate has essentially remained the same and the number of access points is not reduced in a way that increases traffic on the remaining access points then there is minimal on-going impact. But the CMA text merely indicates that this “significant” damage has taken place “since that time” (ie implying it is on a continuous basis, in the past and in future). It converts an historical event as evidence of a future threat.

And it begs the question, do we regard a road culvert as evidence of land degradation? Or do we regard it as a piece of infrastructure that is a normal and necessary part of the prevailing use of the land as a road? Clearly, we view it as the latter. So why do we regard customary tracks (roads) made by cattle for their own continuing use as anything different to our own road culverts?

Both involve an initial excavation that exposes soil and both then involve only minimal soil disturbance for many decades after. And just like our road system, the more traffic cattle tracks have, the greater the visual impact. Do we begrudge Elephants or Caribou their right to shape creek crossings? No, only domestic stock.

To its credit, the site does include some helpful tools for minimising on-going soil movement. And just as for our own road culverts, this involves paving the most prone parts of the road with rock and concrete. The irony is that this simple, logical solution can only be carried out with the approval of DPI and the additional cost and effort that involves. And it is also fairly obvious that any approval for such works would only come with very significant and expensive conditions like fencing off the entire riparian zone and installing unnecessary watering points and piping.

Don’t get me wrong, additional watering points away from streams and dams make very good sense as they spread the grazing intensity more evenly over the entire area. But when faced with baseless, ideologically driven demands to render existing in-stream watering points redundant as a condition of approval for your voluntary good works, most farmers, justifiably, opt to let the authorities continue abusing themselves.


This photo was captioned;
"Sheep are said to have a greater impact than cattle in the riparian zone. (NSW DPI)"

It shows a fairly normal steep bank of a deep riverine cross section. Yes, there are sheep in the picture but one is left to wonder what, exactly, is the impact of those, or the past century of previous sheep, on the steepness of the river bank? Sure, they graze on the grass and may also graze on any tree seedlings that might germinate there. But the chances of such stems surviving the first flood event are quite low as they are more rigid than grass and much more likely to get tangled with passing debris.

Are we to seriously believe that without the sheep this river bank would be steeper? No.
Is there any evidence that the bank is not maintaining its form? No.
Would the bank structure be any different if there were trees atop the bank? No
In fact, if trees were present we would probably observe exposed roots as evidence that additional erosion had taken place. The area of exposed soil would be greater because the grasses would be competing for moisture with the trees and this would present a more erodible face to flood waters with greater potential for snags.


The third photo is just as misleading. We are told; “This creek was severely polluted with sediment and animal waste laden run-off. The rapid increase in nutrient levels caused a massive toxic blue-green algae bloom, rendering the creek water unusable for stock or domestic consumption.”
But what they do not tell us is that this is a temporary condition that starts at the beginning of a dry season and will only last until the pool dries up later in the season. More importantly, they do not mention that most high faecal E. coli counts and algal blooms are the result of self reproduction in the warm stagnant water. As was found to be the case with Canberra’s Lake Burley Griffin, most algae in a bloom is of a secondary or “regrowth” nature.

The severity of an algal bloom or the ultimate concentration of faecal E . coli, is not a function of the initial volume of coli being supplied to the pools in runoff. Rather, the longer the dry season, the warmer the temperature, the shallower the pools and the less frequent the intermittent runoff events take place, the greater the exponential rate of bacterial and algal growth becomes.
Algae reproduce faster and more often in favourable conditions, get used to it, folks.

The official CMA summary is in black type, below. It does not present a true and fair view so we have added a few comments in green to get closer to the truth about the impacts of grazing on riparian zones;

The real impacts of riparian grazing

On-site:
isolated, once-off loss of vegetation cover in the first few years exposure to grazing
once-off soil compaction at a few specific points and initial erosion
once-off bank instability followed by long term stability of the modified landforms
isolated instances of reduced water quality
no evidence of reduced property values from the presence of stock modifications
enhanced germination of native tree species in hoof depressions etc

Off-site:
localised instances of poor water quality (increased turbidity, nutrients and salinity)
very localised loss of in-stream habitat
isolated, once-off changes to river channel shape of minor consequence
minor silting of rivers and creeks compared to that produced by unsealed roads
enhanced natural regeneration of native trees along previously cleared creek banks

Clearly, a picture can, indeed, tell a thousand lies. And government and green pictures seem to tell the most lies of all.

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3 Comments:

At April 08, 2010 2:19 pm, Blogger Dixie said...

Hey Ian you would understand my frustration when I asked a DNR type, I think that was the department tag then, what was the impact of gravel roads in CQ on sediment loads to the GBR. He stated they hadn't thought of that or discussed it in a series of consultations they were involved in at the time on the matter of sediment loads. Did I think they would have one? Wonder why the local councils cart so much of the stuff if it doesn't move. And its getting worse. Our local council used to divert water from gravel roads, under sufferance but they would respect diversion banks and open chocked drains sometimes...but no more. Flat grading ASAP is the only way to go now. Consequently we are one of many landowners only able to use our roads now, since the rain which started on Christmas day. Easy to bog the 4WD before this on roads which are themselves now drains.xie0512

 
At April 08, 2010 4:14 pm, Blogger Ian Mott said...

I have similar problems, Dixie. The council contractors appear to be paid, in part, on the basis of how much additional roadbase they can pile on. And I routinely have to re-open the box drains after each grading. Worse, they routinely leave small bunds of roadbase on the roadside so water cannot flow off the road into the drains anyway. There is not the slightest doubt that few local council road systems would come within cooee of complying with the high standard road management prescriptions adopted by forest owners and managers in their Codes of Practise.
It is no surprise that they have not considered the impact of their own gravel roads on GBR sediment levels. The science has been very clear for nearly 2 decades that an area of gravel road delivers 100 times more sediment than the same area subjected to a clearfall timber harvest. And given that most private native forest harvesting is partial (selective) harvest, not clearfall, then the sediment from that would be 200 to 300 times less than the gravel road.

 
At April 20, 2010 8:12 pm, Blogger Matthew said...

That’s just an incredible landscape. Great photos, especially considering you took them from a plane. landscaping companies sydney

 

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