Nam Et-Phou Louey National Park is a conservation priority for Lao PDR, serving as habitat for many of the nation’s top priority species and as a model of protected area management (Government of Lao PDR 2021). It covers 5,007km2 in the north of Lao PDR; divided into two zones, a 3,000km2 totally protected zone where access and harvest is restricted and a 2,007km2 controlled use zone which is intended for sustainable use by the park’s human communities (Johnson 2012; Government of Lao PDR 2021). The landscape is a mountainous mosaic of forests, bamboo, and grasslands shaped by a long history of human settlement and shifting cultivation (Johnson 2012). There are 91 villages in and bordering the park with a combined population of 42,600 people made up of 8 different ethnic groups, primarily Khamu, Hmong, and Lao (Government of Lao PDR, 2021). The park has been habitat to a wide array of large fauna, many globally threatened; including six species of felid; seven species of primate; two species of bear; Asian elephants Elephus maximus; and over 300 species of birds (Davidson, 1998; Johnson et al., 2006; unpublished observational data). While tiger and leopard have been extirpated from the landscape, the park remains vital to a strong population of clouded leopard Pardofelis nebulosa and dhole Cuon alpinus (Rasphone et al. 2019). A 2015 localized gibbon survey and a subsequent park-wide survey in 2021 revealed a low density but widespread population of northern white-cheeked gibbon Nomascus leucogenys, probably one of the most significant populations of this Critically Endangered primate in the world (Syxaiyakhamthor et al., 2020; unpublished 2021 survey).
Since 2015, Nam Et-Phou Louey National Park management unit, under the Lao Department of Forestry, has mapped deforestation across the landscape using manual digitization of Landsat and Sentinel imagery, digitizing forest clearings by comparing cloud-free images on an annual basis. The fine scale of Sentinel-2 imagery (10 meters) allows it to effectively locate and measure small clearings in forested areas (Lima et al. 2019). Clearings for opium poppy in Nam Et-Phou Louey are typically small (0.15–10 hectares, mean of 0.8 ha) and cleared in areas of remote forest and, unique to crops of the area, planted between September and November (US Department of Justice, 1992; NEPL NP database; author's observations). With knowledge of this trend and with feedback from ranger teams, the park’s spatial data managers have gained confidence in distinguishing opium poppy from clearings for licit crop cultivation and from landslides.
To demonstrate the growth of opium poppy cultivation and its impact on globally threatened species, we selected a rectangular area 704km2 (primarily area legally classed as totally protected zone) in the east of the park and carefully measured the opium fields cleared inside it from 2018 to 2023 using Sentinel-2 satellite imagery. We compared this with encounter rates of cable snares by ranger patrols inside that same rectangle to quantify the hunting threat associated with this cultivation. We also assessed the hunting behaviour of the cultivators from ranger observations and videos posted online by someone associated with this cultivation. Finally, we assessed the comparative risk of extirpation from the hunting which accompanies this cultivation to 61 different faunal species known or suspected to be in the area.
All clearings were digitized from Sentinel-2 images taken between February and April, when opium is harvested, and downloaded from the European Space Agency (ESA) Copernicus Portal (https://scihub.copernicus.eu/dhus/#/home). The method of manual digitization we used was the same as is used by the park management unit. Cloud-free Sentinel-2 images from the same season of two adjacent years are compared with the Swipe Layer Tool, in the Effects toolbar on ArcGIS 10.6, to find changes in pixel colour from dark-green to brown or bright-green (representative of young cultivation). These brown or bright-green pixels are then traced as polygons, tracing the edge of the pixel indicating vegetative conversion from forest. Clearings were selected as opium based on ranger visitations and or timing of clearing. Unvisited clearings near roads and in areas known to be areas of primarily licit cultivation were excluded. Additionally, narrow light-brown/white clearings on the sides of steep slopes are typically representative of landslides and were omitted from the selection. Fields still brown or bright-green the following year were digitized again for that year’s selection; fields having turned dark-green the following year were considered fallow and not digitized.
Field data was collected by trained ranger teams using standardized data collection forms and GPS, stored and analysed using the Spatial Management and Reporting Tool (SMART - https://smartconservationtools.org/). These ranger teams typically operate on 7- or 8-day patrols, on foot, following pre-planned routes but diverge off these routes in the pursuit of confronting violations of natural resource law in the vicinity of their patrols. Examples of events of interest to patrol teams include gun shots, chainsaws, camps, human trails, forest clearing, and snares. These patrol operations have been in place since 2009 and while there have been some changes to strategy and personnel turnover since that time, there were no such major events in strategy, training or personnel during this reporting period. In several cases, opium poppy fields were visited when cultivators were present which revealed where the cultivators were from. From this knowledge we made informed assumptions on which village the cultivator of each field was from and used Point Distance Analysis on ArcGIS 10.6 to calculate the straight-line distance of all fields from the suspected village of their cultivators. Snare encounter rate was calculated for each year as the number of snares encountered by all patrols inside the selected area over 12 months (January – December), divided by the total kilometres of foot patrol inside the same area selection over the same months.
To monitor the behaviour and practice of the opium cultivators, we followed the YouTube channel of someone associated with this cultivation, created in the United States, Hmoob Xamneua (https://www.youtube.com/channel/UCwuM-SPZO6NcCrCZKoN-c9A/videos). Posted on this channel, videos show the owner and colleagues at poppy fields and hunting protected species. Many of these video locations were identified as being in the area of focus through dialogue and distinguishing landmarks.
To bring attention to the species of fauna in this area, at risk of extirpation, we made a list of 61 species known or suspected to be in the area (from biodiversity surveys, opportunistic camera trapping, and ranger encounters). We then combined individual qualitative assessments (from persons familiar with local hunting habits, familiar with the status of the species in question in NEPL, and from experts in the species’ biology and conservation) to rank their comparative risk and identify the threats putting them in that placement. For example, we know clouded leopard to be in the area from opportunistic camera traps installed there in 2021; we know the species to be a target of hunting due to high international demand (Nijman and Shepherd 2015; D’Cruze and Macdonald 2015; Ghimirey and Acharya 2020); we know that the species is susceptible to snaring, hunting with firearms and hunting dogs, and to explosive traps placed inside baited carcasses; from ranger observational data, social media, and past research (Johnson et al. 2006, 2016; Rasphone et al. 2021) we know all these threats to exist in our selected area. Therefore, we rank the risk of extirpation to clouded leopard to be severe, the danger posed by snares to be high, the danger posed by explosives and hunting dogs to be high, and its value as a subsistence food or local-market wildlife meat to be low, but its international demand to be high. This was carried on for all large- and medium-sized terrestrial vertebrates confirmed or highly suspected to be inside the selected area of focus. This table needs to be viewed as an informed speculation on the faunal biodiversity in the area and the risks posed to it from hunting as opposed to the results of a rigorous study.
To undo the sense of secrecy of these fields, the management unit of Nam Et-Phou Louey worked to educate local communities about the effective use of satellite imagery to locate opium cultivation and trained district police agencies in forest navigation and finding of remote fields. Over two cultivation seasons, park rangers posted small, laminated signs in fields notifying the cultivators of (1) the unlawfulness of clearing forest in the totally protected zone and of cultivating opium poppy and (2) of the park’s ability to locate all clearings through satellite imagery. In August and September of 2022, prior to the annual time of preparing fields for planting, Nam Et-Phou Louey management unit visited 15 villages around the park associated with this cultivation with the police of the relevant district and held meetings with representation from every household. On a projector, satellite imagery was displayed and the process for finding fields was explained so that it was understood by all how any clearing made in the forest of the park could be immediately located. Following this outreach, the management unit trained the personnel of these district police units in the use of GPS and maps. Finally, the management unit invited these police personnel to accompany ranger patrols to these fields, giving them practice in forest navigation and teaching them the most efficient routes to all the fields in the area of the park overlapping their respective districts.