Mopane Trees in the Kruger National Park

Jul 18, 2009

Mission: Identify research sites, and search for dead fish and crocodiles
Date: 18 July 2009
Requesting person/organisation: Tony Swemmer of the South African Environmental Observation Network (SAEON)
Location: Kruger National Park
Pilot: Jeremy Woods

In July 2009 we were asked by Tony Swemmer of the South African Environmental Observation Network (SAEON) if we could provide a flight to identify research sites along the southern boundary of the Kruger National Park, and also to search for dead fish and crocodiles in the Olifants River.  Jeremy Woods volunteered to fly this mission for The Bateleurs and SAEON and here is his version of events on the day, followed by a report from Tony Swemmer.

Mopane Trees and Dead Crocodiles
by pilot Jeremy Woods

“Finding AVGAS at a reasonable price in the Limpopo Province is not as easy as you might think.  This I discovered while doing my planning for the mission for SAEON.  The mission was to comprise two separate flights, from Phalaborwa or alternatively Hoedspruit, over the Kruger National Park. None of these places had AVGAS on the field over weekends, and special deliveries from one of the local suppliers would have cost as much as R21.00 a litre – more than double the cost at Rand Airport.  Eventually I located fuel at Tzaneen – 20 minutes flying time to the west, away from the park, and they had fuel at a price cheaper than at Rand!

Our planned departure from Rand to Phalaborwa on Saturday morning didn’t start quite as early as we had hoped.  During our run-up just prior to departure we discovered the right magneto was out.  My son William  was flying with me and he found and fixed the fault – a loose wire to the condenser.  So we took off on the 233nms trip to Phalaborwa and one hour and thirty-three minutes later we were greeting all our passengers in the arrival hall of Phalaborwa Airport.  Tony Swemmer was accompanied by four other observers:  Alan Knapp, Jesse Nippet and Gene Kelly (no, seriously!) from Colorado State University, plus Rodney Landela, the Section Ranger from Kruger Park over whose section we would be flying.

The SAEON mission team, from the left: 
Pilot Jeremy Woods, William Woods, Tony Swemmer (SAEON), Gene Kelly, Alan Knapp, Rodney Landela (KNP), and Jesse Nippet. 
Gene, Alan and Jesse are from Colorado State University.

The first flight was probably a bit rough from a passenger point of view. We flew the entire length of the Olifants River from just inside Kruger all the way to the Mozambique border, and then also a large part of the Timbavati River within the Park. The objective for this flight was to try and spot any dead crocodiles as a result of the ‘hard fat syndrome’ (that’s my name for it) which was highlighted on the 50/50 TV programme a short while ago. This flight would have been uncomfortable for someone who doesn’t fly often.  We were travelling at a height of about 100’ AGL and following the river closely at speeds between 100 knots (185kph) and 130 knots (240 kph). This meant that we were constantly turning sharply and pulling additional G’s in order to keep the river bed visual at all times, as it meanders backwards and forwards through the flat country. When we approached the Mozambique border the river then ‘descends’ into a gorge with high cliffs on either side, and this required rapid height changes as well, causing even more discomfort for our passengers.

The second flight was a little more sedate. The objective for this mission was to survey areas where the Mopane Veld changed to other types of vegetation.  This required flying at heights between 500’ and 1000’ AGL, and sometimes down to about 200’.  At this time of year the Mopane trees were easily identified by their greenish/orange tinge, contrasting with the beige/brown of dry grass and other vegetation.  After a bit of coaching,  my spotting the subtle differences in colour improved.  It appears that specific areas had to be identified where a ‘ground station’ could be located in order to study and monitor the conditions that are causing the spread of the Mopane Veld.  For this flight we were not required to do steep, hard turns:  the slow, sweeping turns with very little additional G forces made for a much more comfortable ride and nobody felt nauseous.  

The two flights together (not including the flights to and from Phalaborwa) amounted to approximately three hours in total.  Tony Swemmer and Rodney Landela accompanied us on both flights, with Jesse Nippet on the first flight and Alan Knapp on the second flight.  The first flight was cut slightly short in the morning because of severe passenger discomfort, but I believe that they obtained all the information they required.

William and I set off for home via Tzaneen in a bit of a rush, hoping that we could still get AVGAS there late on a Saturday afternoon.  We arrived on the ground at Tzaneen well after 16h00 to find the airport totally deserted. We had flown about six hours in total without refuelling and just when we were wondering how we would get into town to overnight there, the petrol attendant appeared.  Hallelujah!  After paying for the fuel and landing fees we headed off on 06, the downhill runway heading away from the mountains, this time routing south to Rand Airport.

By this time I was beginning to feel really tired and I was very pleased to have someone else taking the responsibility for flying home.  We passed over the mountains at Flight Level 085 just before it got dark. Still feeling drained, I was grateful also to have someone strong with me to help push the plane into the hangar when we got back to Rand in the dark. Sleeping in my own bed that night was a bonus, and although  in my dreams I continued to adjust the manifold pressure, DI, mixture, power settings and trim, all night long, I slept the sleep of the righteous.”

A Better Understanding of Mopane Trees and Crocodile Mortalities
by passenger Tony Swemmer


There were two objectives to our Bateleurs-supported flight in July:  The first was to identify suitable research sites along the southern boundary of Mopane trees (Colophospermum mopane) in the Kruger National Park. This was to assist with designing a scientific research project to better understand what factors control the current distribution of Mopane, and make predictions about whether Mopane will spread southwards as global climate change intensifies.  The second objective was to search for dead fish and crocodiles in the Olifants River, within the Kruger National Park. Over the past two years, large numbers of crocodiles and barbel have been dying in this stretch of the Olifants River. The exact cause of these mortalities is not yet known, and rapid detection of new deaths is required both to manage and research this phenomenon.  Aerial reconnaissance is a huge help in searching for dead crocodiles and fish in the more remote parts of Kruger and consequently a Bateleurs-supported flight was arranged for Saturday 18th July 2009.  The research team was hosted by myself, representing the local branch of SAEON, based in Phalaborwa.

The team of visiting scientists from the USA and Rodney Landela (Section Ranger for the Phalaborwa region of the Kruger National Park) were understandably disappointed on the morning of the flight when we were informed that the flight would have to be cancelled due to engine trouble with the aircraft. However, Bateleurs pilot Jeremy Woods called back an hour later to say that the problem had been fixed and after a few hours delay he arrived in Phalaborwa.

From the left:  Alan Knapp, Gene Kelly, Tony Swemmer and Rodney Landela discussing the flight plans for the two routes over Kruger.

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Discussion of the flight plans for two routes over Kruger soon began.  Rodney and I  participated on both flights to assist with navigation over the park. On the first flight, the fourth place in the 4-seater Piper Commanche was taken by Dr Jesse Nippert, an ecologist from Kansas State University. It was decided that we would first check the Olifants River for dead fish and crocodiles as there had recently been a spate of mortalities in the river, particularly in the eastern stretch close to the Mozambique border.

Jeremy headed south from Phalaborwa airport and intercepted the Olifants close to the western boundary of the park. He then carefully navigated along the course of the river, flying at only 100 or 200 feet above the ground.  While Jeremy kept an eye out for eagles and vultures (a potential danger when flying at that height), the rest of the crew scanned the river. Hundreds of hippo were seen sunning themselves on the banks of the river, but very few crocodiles were observed.  Happily no dead crocodiles or fish were seen, but the number of live crocodiles counted (about 15) is cause for concern.  No carcasses have been reported in the river since the flight and the results of this part of the mission confirmed that the spate of fish and crocodile deaths is over (for now).

After flying along the Olifants as far as the Mozambique border, we turned around and flew up the Letaba River from its confluence with the Olifants to the main tar road in Kruger.  Again no carcasses were seen. We then headed north to search for areas on the Kruger’s basaltic plains where dense Mopane vegetation gives way to open grassland. However, the constant banking and turning required to follow the rivers was too much for the two passengers in the back seats, and we decided to re-route back to Phalaborwa to save them from further suffering.

The second flight included Jeremy, Tony and Rodney, again, plus Professor Alan Knapp, an ecologist from Colorado State University, and again the flight initially followed the Olifants River eastwards.  At the confluence of the Olifants and Timbavati rivers, we turned south and began to track the boundary between the Mopane-dominated vegetation and ‘Combretum-acacia’ vegetation which is more typical in the south of the park. The time of the year turned out to be perfect for this exercise, as the orange-tinted leaves of the Mopane trees contrasted clearly with other tree species which had already dropped all their foliage. This enabled us to determine the southern boundary of the Mopane trees from the air.  The extreme south tip of the distribution of Mopane trees (in Africa) was located near Orpen Gate, and after circling this area, Jeremy put us on a course back to Phalaborwa.

Seen from the air the boundary can clearly be seen between Mopane trees,
which dominate vegetation in the northern half of the Kruger National Park,
and the more typical bushveld of the southern half of the Park.

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Mopane-dominated vegetation gives way to riparian trees on the banks of the Olifants River.

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A handheld GPS was used to map patches of Mopane along the boundary, and this information enabled the research team to find suitable research sites on the ground.  There are vast areas of the Kruger that are not accessible by road, and it would have been impossible to identify good research sites along the Mopane boundary from the ground.

This map shows the flight path of Flight 1 (in dark red) that tracked the length of the Olifants River. 
The flight path of Flight 2 is shown in green, and followed the Mopane boundary to the south. 
For Flight 2 the blue flags show patches of Mopane at the edge of its distribution, marked by a handheld GPS. 
Red flags show the location of sites subsequently located for collecting leaf and soil samples.

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Later, at the sites located from the air, samples of Mopane tree leaves and soils beneath them were taken, and the data obtained from the analysis of these samples will be incorporated into a research proposal that the team will submit to the National Science Foundation in the USA.  If successful, the proposal will lead to the creation of a large research project that will run for a minimum of three years and will involve both American and South African scientists. The project will focus on determining why Mopane trees do not occur any further south than they currently do, and whether they are likely to start spreading south as global climate change progresses.  Due to the large negative influence that Mopane trees have on the diversity of ecosystems in the Kruger Park (and the neighbouring private nature reserves), any southward migration of this species will have important consequences for the eco-tourism industry in the Lowveld.

Both objectives of our flight were achieved:  Suitable research sites were found, and the Olifants River was surveyed.  However, more flying will be necessary to accurately map the entire boundary of Mopane trees within the Kruger National Park.”

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