In open areas, like the African savannah, scientists often estimate wildlife populations through manned aerial surveys. However a new study in mongabay.com’s open access journal Tropical Conservation Science argues that using small drones may be more cost-effective, safer, and capable of reaching more remote areas. Researchers tested the accuracy of drone counts in Bazinga Game Ranch (NGR) in Burkina Faso.
Manned aerial surveys “are quite expensive for most African wildlife managers, and it is therefore difficult to plan long-term and regular surveys,” the paper’s authors write. “Consequently, in many African protected areas, the interval between two successive surveys can often be as great as 10 to 25 years. This makes it impossible to quantify accurately the change in wildlife populations. Consequently, some of them simply collapse between two surveys because no appropriate action have been taken.”
Drones have rapidly become a popular tool for conservationists, and have been used to count orangutan nests, monitor recent deforestation, and map out palm oil plantations. Recent test flights have also looked at the potential for drones to monitor marine ecosystems and uncover poachers.
While conducting traditional aerial surveys, researchers count animals along a designated sampling strip. Animals seen outside the strip are not counted, allowing researchers to make estimates based on solid data. However, how does one keep to a sampling strip while using drones? The researchers found that employing an image footprint projection (IFP) resulted in accurate counts. This method beat out using another means to georeference images, known as bundle block adjustments.
“The IFP method can be easily implemented in any GIS software and is not demanding in terms of image quality,” the researchers note. “Moreover, IFP accommodates aerial images with a low level of overlap or even without any overlap.”
However, the researchers cautioned that IFP may not perform so well in rugged region as the flatlands.
“The use of small drones for wildlife surveys as a surrogate for manned aerial surveys is becoming increasingly attractive and has already been implemented with some success,” the researchers write.
- Lisein, J., Linchant, J., Lejeune, P., Bouché P. and Vermeulen, C. 2013. Aerial surveys using an Unmanned Aerial System (UAS): comparison of different methods for estimating the surface area of sampling strips Tropical Conservation Science. Vol. 6(4):506-520.
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