Monitoring vegetation cover remotely

I'm completing my PhD with the Spatial Sciences Group in the School of Biological Sciences at The University of Adelaide in collaboration with Bush Heritage Australia. My research will be conducted at Bush Heritage’s Bon Bon and Boolcoomatta reserves in South Australia.

Remote sensing is a method of collecting information about an area without needing to collect direct on-ground measurements. Photographs provide an easy to understand example of remote sensing - typical platforms used to collect this data include satellites, aircraft and drones. There are several benefits to observing a site with these techniques – including the large area that can be measured and the lack of observer error and bias.

In arid regions, satellite images are commonly used for monitoring land condition. However, monitoring programmes generally focus on condition from the perspective of pastoralism. While an area may be healthy from the perspective of promoting high pastoral productivity, this doesn’t necessarily indicate that the condition of the area is good from a conservation or biodiversity perspective.

This is where my research sits – looking at how remote sensing can be used for monitoring arid land condition for the purpose of conservation.

Boolcoomatta

Visiting Boolcoomatta for the first time in October, soon after the station had received close to 80 mm of rain over the previous month, was a great experience. There was vigorous vegetation growth and birds were present in abundance.

The uncharacteristic condition of the landscape on my first trip became clear when I returned in March, with early responding vegetation now posing as dry, thorny obstacles. Disappointingly, the comparative lack of bird calls was also clear.

This time I was working with the Unmanned Research Aircraft Facility at Adelaide University. We were looking at mapping erosion gullies using drone imagery – a pertinent topic for consideration following such significant rainfall.

We used LiDAR (Light Detection and Ranging) as well as regular red-green-blue (RGB) imagery to map erosion gullies in 3D. By taking several measurements over time, the change in the land surface between dates can be determined. We will test the potential of both methods for providing data that would allow the progression of erosion to be monitored.

Bon Bon – drone-based vegetation surveys

My first trip to Bon Bon was also in March, where I collected the first data for my research - drone surveys of several one-hectare plots around the reserve.

As mentioned earlier, current remote sensing programmes for rangeland vegetation monitoring don’t necessarily take biodiversity and conservation into account. This is partially because the assessment of indicators for biodiversity, such as species diversity, tree canopy health, shrub cover, etc., requires relatively high-resolution imagery. This is difficult to achieve with freely available satellite imagery.

Flying the drone at 30 m above the ground, a one-hectare area was able to be captured in around seven minutes. The image captured had individual pixels that each represent less than one square centimetre on the ground.

Into the future

In the first written component of my project, I'm looking at traditional indicators for ecological diversity and assessing the current development of remote sensing methods for each. Remote sensing methods can range from fully operational (employed in monitoring programmes), through to purely conceptual. Identifying which indicators can benefit from remote sensing is essential in pushing research and development and ensuring the progression of new techniques through research and testing phases into operational monitoring programmes.

Based on the drone data collected at Bon Bon, in another section of my research I will make a comparison between the information that can be extracted from this imagery and information that is collected using Bush Heritage’s line-intercept monitoring protocol.

I will also use remotely sensed data to observe how vegetation at Bon Bon and Boolcoomatta has changed since their acquisition by Bush Heritage. I'll then investigate how any change in vegetation is related to management actions and climatic variables. If this research can provide a better understanding of how different management and natural variables affect vegetation and biodiversity it will assist Bush Heritage and other management groups in managing land to maintain and restore natural conditions.

This project is being partially supported by the Thyne Reid Foundation