Workshop highlights the importance of satellites in Kruger’s conservation

By Melissa Wray and Izak Smit In Kruger National Park

Imagine being able to effectively monitor any changes in the vegetation across the whole of the Kruger National Park’s two million hectares, seeing the effect of fires or spots of bush encroachment or erosion patches or many other things – from the comfort of an air-conditioned office in Skukuza, Johannesburg or in fact anywhere in the world. 25 scientists from around South Africa met in Skukuza on November 13, 2006 to discuss just this possibility, in a pioneering remote sensing workshop for the park. Remote sensing is the gathering of information about things on the earth’s surface without actually setting foot in the area. For decades Kruger has been developing a remote sensing archive in the form of aerial and fixed point photographs.

The photos are taken from the same places year after year, making it possible to see changes in the park’s landscapes over time. However, Kruger’s scientific services have been moving with the times, and that means supplementing the tried and true methods of remote sensing with new technology - satellite imagery. Since Sputnik 1 was launched into space in 1957, becoming the first man-made object to orbit the earth, the sky above us has become littered with hundreds of satellites. These satellites are sent into space by different countries and with different missions in mind, from predicting the next thunderstorm to predicting the next world war.

For the last several years Kruger has been using data sent from a satellite called MODIS to map the scars that fires make in the park’s vegetation. The GIS (Geographic Information Systems) and remote sensing laboratory gets data from the MODIS satellite twice a day, and can verify quite accurately how much of each section of the park has been burnt without setting foot outside the office. But this ability to map fire scars in air-conditioned comfort is still based on some initial work done walking over blackened stubble under the hot sun to verify the link between the reality on Kruger’s soil and the image beamed down from the sky. This is known as ‘ground truthing’ and is an important step in turning remotely sensed data into userfriendly information.

ADVANTAGES

For an area the size of Kruger, the advantages of remote sensing become obvious. If a ranger had to be sent out into the field after every fire to go and check exactly where it stopped so that they could better predict where other fires might start up, no one would get much other work done in fire season. Training a computer to recognise fire scars from a satellite image speeds up the process significantly, and allows management to coordinate planned burns and other issues. In much the same way, remote sensing boffins can use data sent from satellites to reveal many other things, from rivers drying up to the planting of cocaine in the rainforests of South America.

According to Izak Smit, Kruger’s research manager for GIS and remote sensing, the scientists present at the workshop were confident that using current technology, remote sensing could contribute to monitoring the woody vegetation structure (ie horizontal coverage of trees on the ground and their height structure classes), the herbaceous layer (the ground coverage and relative amount of grasses and other small plants that are not bushes or trees) and fire in Kruger. “It was also recognised that remote sensing techniques would never be able to replace fieldbased monitoring, but would be able to contribute to monitoring on space and time scales previously not possible.”

Remotely sensed data can also allow one to see the whole of Kruger at any given time at a glance, as well as offering the opportunity to monitor what is going on in the areas neighbouring Kruger. This includes adjoining protected areas like the Limpopo National Park and the private nature reserves to the west of Kruger, but also the communities and developments on the park’s boundaries. This ability to see and think outside of Kruger’s fences is helpful for such issues as the state of the rivers in the park, as what goes on outside Kruger has a huge effect on river health in the park.

Scientists can use satellite data in many different ways, partly because there are many types of data that are generated by the ‘eyes in the sky’. Kruger already has an archive of data sets, or images, from seven different satellite systems, and more can be expected in future. The satellites all have different orbit times, passing over Kruger anywhere from once every 12 hours to once a month. They also have different abilities. One of the satellite images that Kruger has for the Skukuza area can produce a black and white image that is so detailed that the lines in the golf course’s parking lot are visible, while another reduces one kilometre on the ground into a single dot on a computer screen.

LINKING DATA

One of the many virtues of satellite imagery is that a single satellite will normally record more than just the equivalent of a digital photograph of the earth (like Google Earth uses) but also information from many of the different wavelengths of the electromagnetic spectrum from the shorter wave visible blue light to the longer wave thermal infrared. By linking this information up with data on the ground, such as that gathered by the section rangers in their regular vegetation monitoring, the data sets can be manipulated to reveal what is going on in areas of the park where no monitoring is done, or where there is no access.

The more data the park has, the easier it is to see trends over space and time, and therefore to enlighten debates on management issues. Bearing this in mind, the remote sensing workshop brought together some of the top remote sensing people in the country to create a framework that “will ensure a more directed, coordinated and collaborative approach is followed in future remote sensing research in the park, specifically focussing on using remote sensing for addressing some of Kruger’s monitoring priorities on different scales and in a cost effective manner.”

The Skukuza GIS lab is a central repository of remotely sensed data about Kruger, which supplies imagery to scientific services and researchers who have registered projects in the park. A clearly defined framework of the way forward for Kruger in terms of remote sensing monitoring will be finalised early next year. As Izak comments, “This workshop and the efforts evolving from it provides a clear message that Kruger, even though it is one of the oldest proclaimed protected areas in the world, embraces new technology