BUFFER ZONES ROUND LAKES, RIVERS AND STREAMS NO LONGER A REQUIREMENT AT 1080 POISON DROPS
By Carol Sawyer
Someone has just asked me if having GPS in a helicopter means 1080 poison baits do not need to be dropped into waterways – i.e.that streams and waterways could be avoided.
Well, yes, but ag pilots tell me, and Murray Dench also explains this quite well in the post below) that, even with GPS, bait-dropping can only be accurate with some certainty to within a minimum of 200 metres, and even then, so-called ” overflies” happen (i.e. baits land outside the drop zone).
A good example of an “overfly” was the Kepler Mountains drop at Lake Manapouri in Spring 2016 when a 200 ha area outside the drop zone was covered in 1080 baits by HeliOtago.
(Even though protestors were initially blamed for this, HeliOtago later admitted the cause was that their pilots were under pressure to finish the job).
However the new government rules are that NO stream or waterway needs to be avoided by helicopters dropping 1080 poison, so the question of GPS accuracy and bait-dropping is somewhat academic!
Even when buffer zones are set around waterways, they tend to be woefully inadequate. In Febuary 2017, at the 1080 poison drop at Makarora, a 20 metre buffer zone was applied to the Makarora and Wilkin Rivers, yet baits were found in these rivers after the poison drop.
Below is Murray Dench’s report:
DROPPING 1080 POISON FROM THE SKY IS NOT AN ACCURATE PROCESS
In 2007, following the ERMA Review, Murray Dench wrote to Andrea Eng, General Manager Hazardous Substances, ERMA on Differential Global Positioning Systems with regard to dropping 1080 baits. What he wrote is very interesting. Here it is :
“The distribution of the baits from a helicopter is far from certain. While DGPS has allowed more accurate placement of the aircraft there are other factors involved :-
1. The groundspeed of the machine during the delivery run.
Over level terrain this is quite easily controlled but over steep terrain (where the helicopter is most ‘useful’) every act of climbing and descending to match the contour changes the ground speed.
This is difficult to control because the pilot (if he’s smart) will be concentrating on terrain avoidance and personal welfare to the detriment of accurate groundspeed monitoring.
Another negative factor is wind speed and its degree of crosswind (or even tail wind) component. Again, in level terrain the crosswind component is relatively constant and can be allowed for but in broken country wind changes are legendary including lift, lee turbulence, rotor action, and a raft of others which sensible pilots do their best to avoid.
The changing wind speeds and directions rapidly change the aircrafts airspeed indication for which the pilot must compensate to maintain the target groundspeed. It also rapidly changes the aircraft direction of travel and rate of climb which has to be constantly corrected. When you combine terrain avoidance with constant altitude changes and violently changing wind speed and direction it is not hard to see that accurate distribution of baits is not likely.
2. The height of the machine above the ground during the delivery run.
It is assumed that the hopper delivery system is designed to produce a certain pattern on the ground when delivered from a certain height. If the delivery is from a lesser height then the pattern will not have reached its full dimension and a narrow strip of high bait concentration will be laid. If the delivery is from a greater height than the target then the delivery pattern may be wider with reduced bait density. If delivery from the ideal height results in the baits falling vertically downwards then distribution from a greater height is okay except that the baits are longer in the air and are therefore more susceptible to wind currents moving them out of the intended delivery zone. Trying to maintain an accurate height above ground in steep and broken country while trying to maintain groundspeed and avoid terrain creates a scenario ripe for failure.
3. Accurate delivery relies on the baits exiting the hopper and dropping onto the spinning distribution disc at a constant rate.
This is highly unlikely. The greater the head (weight) of baits in the hopper the greater is the pressure available to push the bottom baits out. As the hopper level reduces the pressure reduces and so the flow of baits also reduces. It is possible that there is some compensation for this negative affect provided by the reducing friction losses against the hopper walls as the hopper level falls but given slippery carrots and free flowing cereal baits it is hard to imagine this mitigation being enough. It is a pretty safe bet that the distribution density of baits at the start of a run is greater than at the end.
4. Overlap.
If a circle of material is continuously dropped while in motion then the path along the centre line of the circle will receive twice as much material as the edges. This is because the material which is thrown forward is added to by the material which is thrown backwards over exactly the same path whereas the material thrown to the extreme edges cannot be duplicated. This provides a distribution pattern with the highest concentration along the centreline of the direction of travel gradually reducing to the minimum distribution density along both edges. It is not possible to produce an even distribution density from a moving 360° rotating disc. It is assumed the applicators mitigate against this effect by overlapping each delivery run so the low distribution density strips along the edges are ‘double dosed’ to achieve the target density.
Again it is assumed this need to overlap is programmed into the tracks to be flown under GPS guidance but is another error inherent in the entire delivery system.
Unintended by-kill is closely correlated with bait distribution.
Having a DGPS in the cockpit of the delivery aircraft is certainly a help but many other factors need assessment and controls added to improve the chance of accurate delivery.
ERMA failed to investigate and understand the variables associated with bait delivery and how poor distribution might easily result and instead nominated DGPS as a ‘cure all’ which it cannot be.”
Look closely at the photo above in the header image and you will see baits flying in all directions. This helicopter is low to the bush. Imagine that same helicopter at height and you can start to realize the inaccuracy of a bait drop.
Environmental Health Watch NZ 