Friday, December 31, 2010

Are we really sure excluding cattle from the Barmah Forest is a good idea?

Are we really sure excluding cattle from the Barmah Forest is a good idea?

I would argue we can't be sure, and that the exclusion was done so fast & unilaterally that it likely to have a number of unforeseen affects.

Earlier this month I saw "Out of the Scientist's Garden" by Richard Stirzaker, CSIRO Land & Water Australia Senior Research Fellow at Cooperative Research Centre (CRC) for Irrigation Futures, in a local bookshop. Did a quiet skim in the bookshop and borough it.

Got I home and after a few more minutes browsing, I realised I'ld seen him speak & been to his then home in the early '90 to see his back yards 'Clever Clover' plot. There are photos of that back yard in the book.

On further reading I found the following passage on pages 171 & 172, in Chapter 20: Simplicity.

A couple of notes first. Roan are a large antelope that can get to over 250 kgs. The park being talked about is the Kurger National Park in South Africa.
Roan tend to favour area growing taller, less palatable grasses. They wander over large areas of savannah, picking the few tender young leaves from the grassy tussocks. Zebras and wildebeest are more like lawn mowers. They concentrate in huge numbers on the more fertile soils which more palatable grasses, and by grazing patches of the savannah heavily, they ensure a continuous supply of nutritious young leaves.

Roan must cover large distances to select their diet, but they are also very dependent on water. There are large area of park with grazing suitable for roan, but without rivers for the roan to drink. So park managers put in windmills to pump ground water into troughs. The plan worked spectacularly well. The roan spread out over a much larger area around the new sources of water. The still occurred at low densities because the grasses in the region tended to be of lower quality, but their numbers steadily increased.

Over the years, the new water attracted other grazers, particularly zebra and wildebeest. Although the dominant grass was not ideal for these species, they changed some areas with their constant heavy grazing, producing lawn-like areas of young, more palatable grass. In doing so, the density of herbivores increased, and this did not escape the attention of the loins.

Since zebra and wildebeest are the favoured prey of loins, they get a lot of practice spotting predictors and running to safety. Not so the roan. Hunting had been an unprofitable business for loins in the area prior to the new watering points, because of the low densities of prey. Now the loins switched their attention from the ever vigilant zebras to the unsuspecting roan. Roan numbers started to go down alarmingly.

The solution of adding new watering points was put into reverse. The bores were closed and, as predicted, the zebras drifted back to more favourable areas. As always the loins followed them, but not all the loins. A few prides took up residence in the roan areas. They changed their hunting habits. No longer could they hang around the plentiful herds and ambush them at waterholes on the short-grass plains. They started wandering widely, and met up frequently enough with the meandering roan to virtually wipe them out.

It all begs the question of is this being done just to satisfy political needs in Melbourne. The Kruger reversal was done after a few year. The Barmah reversal is being done after well over a century. The lesson of Kruger is that it should be done using a phased approach with control area to compare with. I don't mean little 10 by 10 metre experiments. That scale of research is just preliminary for the real experiment of introducing a new system to the forest.

Is removing the cattle a diversion for not getting water right? My understanding is that the Red Gums aren't getting inundated often enough and that particularly the higher areas are missing out. That cattle are only grazing pressure after the fact?

Cattle grazing would be removing fire fuel load too. Sound like swing-and-round-a-bouts to me.

Given the about story I would think the safest way to proceed is to divide the forest into many zones and spell zones from any grazing for 10 or 20 years after inundation in a long term rotation. Keep the fuel loads low while allowing long periods from germination & establishment after inundations.

What do you think?

1 comment:

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