Tropical forests are often located in difficult-to-access areas, which make high-quality forest structure information difficult and expensive to obtain by traditional field-based approaches. LiDAR (acronym for Light Detection And Ranging) data have been used throughout the world to produce time-efficient and wall-to-wall structural parameter estimates for monitoring in native and commercial forests. In this study, we compare products and aboveground biomass (AGB) estimations from LiDAR data acquired using an aircraft-borne system in 2015 and data collected by the unmanned aerial vehicle (UAV)-based GatorEye Unmanned Flying Laboratory in 2017 for ten forest inventory plots located in the Chico Mendes Extractive Reserve in Acre state, southwestern Brazilian Amazon. The LiDAR products were similar and comparable among the two platforms and sensors. Principal differences between derived products resulted from the GatorEye system flying lower and slower and having increased returns per second than the aircraft, resulting in a much higher point density overall (11.3 ± 1.8 vs. 381.2 ± 58 pts/m2). Differences in ground point density, however, were much smaller among the systems, due to the larger pulse area and increased number of returns per pulse of the aircraft system, with the GatorEye showing an approximately 50% higher ground point density (0.27 ± 0.09 vs. 0.42 ± 0.09). The LiDAR models produced by both sensors presented similar results for digital elevation models and estimated AGB. Our results validate the ability for UAV-borne LiDAR sensors to accurately quantify AGB in dense high-leaf-area tropical forests in the Amazon. We also highlight new possibilities using the dense point clouds of UAV-borne systems for analyses of detailed crown structure and leaf area density distribution of the forest interior.

Protected areas are key to biodiversity conservation and ranger-based monitoring, and law enforcement is the cornerstone upon which effective protected areas are built. Frontline practitioners, however, are often asked to protect large swathes of land or sea with limited resources, support, infrastructure, capacity, and/or training. Technology, when applied effectively and appropriately, has the capacity to empower practitioners, revolutionize ranger operations, improve ranger safety, and enhance wildlife protection and conservation outcomes. To do so, technology must be recognized, from the frontlines through to key decisionmakers, as a force multiplier, but only when it is fit for purpose, accessible, cost-effective, and supportive of rangers' needs. In this paper we detail the general state of conservation technology and innovation within the ranger context and provide a series of detailed recommendations to help the Universal Ranger Support Alliance (URSA) meet the needs of rangers around the world, including: demystifying technology and clarifying what it can and cannot do, connecting the right technology with the right people and places, focusing technology development and investment on substantive improvements and support, broadening ranger familiarization with technology, building technology capacity in rangers, fostering greater community building and creating opportunities around technologies, engaging the technology sector to innovate and design technology to support rangers, and supporting technology as a complement to traditional knowledge and skills, rather than a replacement. These recommendations constitute an ambitious vision which cannot be delivered by URSA in isolation. Rather, we propose URSA leverages existing efforts to ensure rangers are supported around the world.

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