Satellite-based Illegal logging Detection with Amnesty International
Figure 1.The area of interest is the two protected areas of Cambodia: Prey Preah Roka wildlife sanctuary ( 13°57'35.72"N, 105° 9'15.45"E), Prey Lang Rainforest ( 13°18'31.58"N, 105°35'37.41"E)
New research from Amnesty International conducted in 2021 reveals how illegal logging of protected forests is destabilizing human rights and destroying the traditions of indigenous peoples in Cambodia. The report revealed insights into how pervasive deforestation combined with corruption and government restrictions of access to protected areas have ‘threatened indigenous communities’ cultural survival, land rights, livelihoods, and reduced their ability to protect the forest’. Cambodia is home to around 24 different indigenous peoples while also experiencing some of the highest rates of deforestation, losing around 64% of its tree cover since 2011 [source]. To add to this dynamic, the rate of deforestation in Cambodia is growing rapidly. A report produced by the University of Maryland in partnership with GFW (Global Forest Watch) revealed that over 9,000 hectares of forest were lost during 2020. Additionally, around 20% more trees were lost in 2020 than in 2019 [source].
In the face of increasing concerns, Amnesty International collaborated with Space4Good to leverage earth observation technology to detect recent deforestation in two of the protected areas of Cambodia: Prey Preah Roka wildlife sanctuary and Prey Lang Rainforest (Fig. 1). Our results estimated that at least 6,025 hectares of forest were logged in Prey Lang and 246 hectares in Preah Roka over that 12-month period (Fig. 2).
Figure 2 Deforestation detected in 2021 using ESA Sentinel-1 data.
Due to a lack of access to the protected areas, Amnesty International reached out to Space4Good to conduct an analysis with remote sensing data to detect deforestation in 2021 in both protected areas. In order to detect the deforested areas with very high confidence, our remote sensing team used a combination of radar and optical satellite imagery mosaic analytics. Deforestation detections were issued using European Space Agency (ESA) Copernicus Synthetic Aperture Radar (SAR) Sentinel-1 20m spatial resolution data to determine a baseline. An adaptive thresholding method was applied to the multi-temporal images. We then cross-verified these detections using a Normalized Difference Vegetation Index (NDVI) with Planet Labs’ Planetscope Surface Reflectance Mosaics with 4.77m spatial resolution.
To ensure accuracy, when areas were only partially overlapping (for example, the Sentinel detection covered a larger area than the Planetscope detection), the detected areas were adjusted to achieve the higher accuracy needed to determine and report deforestation. It is important to note that in other cases, using higher-resolution remote sensing data sources combined with ground surveys could have revealed even higher rates of deforestation. We believe that as more insights become available using additional datasets (for example, Capella), further deforestation is likely to be revealed and work to prevent this crime can become more effective.
We thank Amnesty International for including us in this important work and look forward to supporting similar projects seeking insights and predictions into illegal logging. A more detailed report about the project has been published by Amnesty International [link] and further expanded on by articles from the Guardian and Radio Free Asia.
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