Forestry in South Africa
Monday, August 8, 2022

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CSIR Articles : Detection of large-scale landscape changes in and around the Kruger National Park

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Detection of large-scale landscape changes in and around the Kruger National Park 

The Carnegie Airborne Observatory (CAO) - an integrated airborne hyperspectral and light detection and ranging (LiDAR) system based at Stanford University in the United States - recently completed a third mission to the Kruger National Park (KNP) in South Africa. This means that remote sensing specialists in South Africa now have access to three sets of biennial data dating back to 2008 and stretching over an area of 65 000 hectares.

The LiDAR system is mounted inside an aircraft and sends out a continuous flow of laser shots that provides maps of the height and internal structure of the vegetation in 3D, and at remarkably good resolutions.

 CSIR - Members of a team from the CAO, KNP, CSIR and Wits that detects change over the KNP area.

Working in collaboration with the CAO, SANParks and the University of the Witwatersrand, the CSIR's Earth observations research groups have achieved several milestones, changing the way large areas like the KNP and surrounding areas can be managed.

According to Prof Greg Asner, professor at the Department for Global Ecology at Stanford University and in charge of the CAO, their relationship with South Africa is quite unique: "It is one of the only places in the world where we work directly with local scientists on issues of management conservation. Working in South Africa with the Kruger National Park and the CSIR gives us the chance to have real impact," he said during an interview at the time of the CAO's third mission to the country in April 2012.

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This sentiment is echoed by SANParks' research manager for GIS and remote sensing, Dr Izak Smit: "We do not have the infrastructure, technology or expertise to deal with a project of this magnitude. Yet, working with external partners, we can leverage the expertise and funding, thereby enriching our work in transforming the science into management decisions and practices.

"We find ourselves at the interface between the science and the management of the parks. Collaboration with external partners like the CSIR, universities and the CAO is essential to the successful management of the parks, and has had impacts on how we manage the park when it comes to the provision of water holes and prescribed burning, for example."

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For Dr Renaud Mathieu, a CSIR principal scientist, the collaboration is also about building technical skills and capacity in South Africa to process large sets of data and developing remote sense technologies well suited to the South African savannah landscape.

"Historically, especially in Africa, most remote sensing-based approaches focused on tropical deforestation. However, more than half of the southern African subcontinent is covered with savannah with about 10 to 50% tree cover and undergoing mostly gradual changes such as bush encroachment or tree logging for fuelwood. Techniques developed for assessing woody biomass in tropical forests with dense canopies cannot simply be transferred to savannas and woodlands," he explains.

Futhermore, the long-term vision is to develop the whole LiDAR value chain, including the local capacity to operationally collect LiDAR data for environmental management and vegetation applications using local airborne survey companies. In this regard, the CSIR and SANParks are already working with a South African company to test the viability, as SANParks is considering using LiDAR surveys for long-term monitoring.

Research milestone: Sustainability of fuelwood for rural energy needs

The LiDAR data from the 2008 flight campaign have enabled researchers to map and measure woody biomass in rural areas such as Bushbuckridge, where harvesting of live wood is still the primary source of fuel for cooking and heating even when electricity is available.

Researchers combined the LiDAR data with socio-economic data collected from the area over the past 20 years by the Wits Rural Public Health and Health Transitions Research Unit, and the WITS programme for Sustaining Natural Resources in African Ecosystems.

This shows that at the current rate of fuelwood consumption - three to four tons per year per household - the woodland resources for some rural villages in Bushbuckridge may only last another 12 years. With the help of the LiDAR data and fieldwork, researchers have also found evidence of illegal commercial cutting of fuelwood in the communal rangelands.

"There is great concern that the current levels of utilisation are not sustainable, with direct negative impacts on the poor, as well as for biodiversity loss and conservation. Our findings to date regarding the sustainability of this ecosystem service warrant further investigation," says Dr Mathieu.

In all instances, improved estimates will be instrumental to poverty alleviation.

Research milestones: Loss of big trees in conserved areas

Another significant finding is that large herbivores and fires may have a bigger impact on the loss of big trees in conserved areas than in communal areas, where large trees like the Marula are valued for their fruits. Over five metres high, many of these trees have taken over 50 years to grow.

Dr Mathieu, "We have detected a 20% loss of big trees from research sites in a private game reserve next to the KNP in just two years,


compared to a 10% loss of big trees from research sites on communal land over the same time period." 

This was also the first time in his remote sensing career that he found a 100% correlation between prediction of a remote sensing system (the LiDAR) and ground verification.

But researchers are still puzzled about why and how this is happenin. 

"At the moment, we think it is because of different reasons," explains Dr Mathieu: "In the case of the private game reserve, field work shows that a combination of elephants and fire damage is involved. For instance, the elephants push and debark the big trees. The trees are weakened, and then burn more easily in veld fires."

In the communal areas, trees are cut for building posts for field fencing and fuel wood; however, it is a big taboo to cut big fruit-bearing trees like the Marula, and people mostly cut the lower-growing trees and bushes.

Again, this finding needs to be further investigated and interrogated. For the remote sensing specialists in South Africa, the recent 2012 CAO campaign will be useful to confirm or infirm these results over a wider area and a longer time span.