Climate-Change-Driven Droughts and Tree Mortality: Assessing the Potential of UAV-Derived Early Warning Metrics

Abstract

Protecting and enhancing forest carbon sinks is considered a natural solution for mitigating climate change. However, the increasing frequency, intensity, and duration of droughts due to climate change can threaten the stability and growth of existing forest carbon sinks. Extreme droughts weaken plant hydraulic systems, can lead to tree mortality events, and may reduce forest diversity, making forests more vulnerable to subsequent forest disturbances, such as forest fires or pest infestations. Although early warning metrics (EWMs) derived using satellite remote sensing data are now being tested for predicting post-drought plant physiological stress and mortality, applications of unmanned aerial vehicles (UAVs) are yet to be explored extensively. Herein, we provide twenty-four prospective approaches classified into five categories: (i) physiological complexities, (ii) site-specific and confounding (abiotic) factors, (iii) interactions with biotic agents, (iv) forest carbon monitoring and optimization, and (v) technological and infrastructural developments, for adoption, future operationalization, and upscaling of UAV-based frameworks for EWM applications. These UAV considerations are paramount as they hold the potential to bridge the gap between field inventory and satellite remote sensing for assessing forest characteristics and their responses to drought conditions, identifying and prioritizing conservation needs of vulnerable and/or high-carbon-efficient tree species for efficient allocation of resources, and optimizing forest carbon management with climate change adaptation and mitigation practices in a timely and cost-effective manner.

The Detection of Tree of Heaven (Ailanthus altissima) Using Drones and Optical Sensors: Implications for the Management of Invasive Plants and Insects

“…The temperature of both the background and the seed clusters appeared similar, with no temperature distinction being observed. The NDVI sensor was not able to detect A. altissima in any season of the year, but it holds potential for evaluating the effectiveness of A. altissima control [41]; after successful control, causing the death of A. altissima, it should be detectable via the use of the NDVI sensor, as there should be no healthy vegetation remaining. Drones can be flown when wind speed is below 27 kph, following the regulations of the Federal Aviation Administration (FAA) of the USA [42].…”

Influence of urban forests on residential property values: A systematic review of remote sensing-based studies

“…RS technologies - especially LiDAR and high-resolution imagery (e.g., Planet data) can be used to monitor and measure urban forests aboveground biomass, which is used to estimate the amount of sequestrated carbon and calculate the carbon credits of urban forest types, which can then be reflected in residential property prices. With UAVs, growth status of recently planted trees can also be derived, which could lead to tapping into ex-ante carbon credits [ 44 ].…”

“…UAVs imagery offers high spatial resolution data [ 44 , 116 , 118 ] in a cost effective and time efficient manner [ 118 ]. Isibue and Pingel [ 118 ] used UAV data to produce estimates of tree height in the urban environment and concluded that the results from UAVs is comparable to manual field measurement [ 118 ] and even better than conventional aerial LiDAR [ 116 , 118 ].…”

“…The accuracy of remote sensing-derived forest, tree and vegetation metrics have been improving with the advancements in machine learning algorithms combined with multi-temporal LiDAR (Light Detection and Ranging) point clouds and UAV (Unmanned Aerial Vehicles) images. It also allows for extracting finer details, patterns, and changes in information on forests, tree-level and vegetation characteristics and indices with lower costs [ [44] , [45] , [46] , [47] ]. Remote sensing-derived forests and tree-level data are important input variables for inclusion in hedonic pricing models to improve our understanding of the relationship between urban forests and residential property prices.…”

The Multidimensional Threats of Unmanned Aerial Systems: Exploring Biomechanical, Technical, Operational, and Legal Solutions for Ensuring Safety and Security

“…Unmanned aerial vehicles, also known as drones, are playing an increasingly significant role in the functioning of the modern world, becoming an integral part of numerous economic sectors. These devices are widely utilized, aiding in tasks such as military operations, surveillance, monitoring, transportation, data gathering, and entertainment (Bielawski et al, 2018;Perz et al, 2018;Ewane et al 2023, Pietrzykowski et al, 2022. The rising popularity of UAVs stems from their unique features, such as remote control capabilities, programmable flight trajectories, accident investigation as well as the ability to mount advanced monitoring and measurement instruments (Pompigna et al, 2022).…”