• Energy Research

AbstractEcosystems in the North American Arctic-Boreal Zone (ABZ) experience a diverse set of disturbances associated with wildfire, permafrost dynamics, geomorphic processes, insect outbreaks and pathogens, extreme weather events, and human activity. Climate warming in the ABZ is occurring at over twice the rate of the global average, and as a result the extent, frequency, and severity of these disturbances are increasing rapidly. Disturbances in the ABZ span a wide gradient of spatiotemporal scales and have varying impacts on ecosystem properties and function. However, many ABZ disturbances are relatively understudied and have different sensitivities to climate and trajectories of recovery, resulting in considerable uncertainty in the impacts of climate warming and human land use on ABZ vegetation dynamics and in the interactions between disturbance types. Here we review the current knowledge of ABZ disturbances and their precursors, ecosystem impacts, temporal frequencies, spatial extents, and severity. We also summarize current knowledge of interactions and feedbacks among ABZ disturbances and characterize typical trajectories of vegetation loss and recovery in response to ecosystem disturbance using satellite time-series. We conclude with a summary of critical data and knowledge gaps and identify priorities for future study.

Abstract Accurate estimation of aboveground forest biomass stocks is required to assess the impacts of land use changes such as deforestation and subsequent regrowth on concentrations of atmospheric CO2. The Global Ecosystem Dynamics Investigation (GEDI) is a lidar mission launched by NASA to the International Space Station in 2018. GEDI was specifically designed to retrieve vegetation structure within a novel, theoretical sampling design that explicitly quantifies biomass and its uncertainty across a variety of spatial scales. In this paper we provide the estimates of pan-tropical and temperate biomass derived from two years of GEDI observations. We present estimates of mean biomass densities at 1 km resolution, as well as estimates aggregated to the national level for every country GEDI observes, and at the sub-national level for the United States. For all estimates we provide the standard error of the mean biomass. These data serve as a baseline for current biomass stocks and their future changes, and the mission’s integrated use of formal statistical inference points the way towards the possibility of a new generation of powerful monitoring tools from space.

This paper presents an overview of the state of measurement and monitoring capabilities for forests in the context of REDD+ needs, with a focus on what is currently possible, where improvements are needed, and what capabilities will be advanced in the near-term with new technologies already under development. We summarize the role of remote sensing (both satellite and aircraft) for observational monitoring of forests, including measuring changes in their current and past extent for setting baselines, their carbon stock density for estimating emissions in areas that are deforested or degraded, and their regrowth dynamics following disturbance. We emphasize the synergistic role of integrating field inventory measurements with remote sensing for best practices in monitoring, reporting and verification. We also address the potential of remote sensing for enforcing safeguards on conservation of natural forests and biodiversity. We argue that capabilities exist now to meet operational needs for REDD+ measurement, reporting, and verification and reference levels. For some other areas of importance for REDD+, such as safeguards for natural forests and biodiversity, monitoring capabilities are approaching operational in the near term. For all REDD+ needs, measurement capabilities will rapidly advance in the next few years as a result of new technology as well as advances in capacity building both within and outside of the tropical forest nations on which REDD+ is primarily focused.

Nature Sustainability, 2 (7) ISSN:2398-9629

AbstractThe snow‐masking effect of vegetation exerts strong control on albedo in northern high latitude ecosystems. Large‐scale changes in the distribution and stature of vegetation in this region will thus have important feedbacks to climate. The snow‐albedo feedback is controlled largely by the contrast between snow‐covered and snow‐free albedo (Δα), which influences predictions of future warming in coupled climate models, despite being poorly constrained at seasonal and century time scales. Here, we compare satellite observations and coupled climate model representations of albedo and tree cover for the boreal and Arctic region. Our analyses reveal consistent declines in albedo with increasing tree cover, occurring south of latitudinal tree line, that are poorly represented in coupled climate models. Observed relationships between albedo and tree cover differ substantially between snow‐covered and snow‐free periods, and among plant functional type. Tree cover in models varies widely but surprisingly does not correlate well with model albedo. Furthermore, our results demonstrate a relationship between tree cover and snow‐albedo feedback that may be used to accurately constrain high latitude albedo feedbacks in coupled climate models under current and future vegetation distributions.

Here we response to a Letter to the Editor by Timoney (2022) and maintain our conclusion that "there have been systematic trends in vegetation greenness during recent decades that are consistent with an emerging boreal biome shift associated with ongoing climate warming."

Le changement climatique et les taux élevés d'émissions mondiales de carbone ont attiré l'attention sur la nécessité de systèmes de surveillance de haute qualité pour évaluer la quantité de carbone présente dans les systèmes terrestres et son évolution dans le temps. Le choix du système à adopter doit être guidé par une bonne science. Il existe un nombre croissant d'informations scientifiques et techniques sur les méthodes de mesure du carbone au sol et par télédétection. L'adéquation et la comparabilité de ces différents systèmes n'ont pas été pleinement évaluées. Un examen systématique comparera les méthodes d'évaluation des stocks de carbone et des changements des stocks de carbone dans les principales catégories d'utilisation des terres, y compris les terres forestières, les terres cultivées, les prairies et les zones humides, dans les réservoirs de carbone terrestres qui peuvent être pris en compte dans le protocole de Kyoto (biomasse aérienne, biomasse souterraine, bois mort, litière et carbone du sol). L'évaluation du carbone dans les produits ligneux récoltés ne sera pas prise en compte dans cette revue. L'élaboration de stratégies d'atténuation efficaces pour réduire les émissions de carbone et de stratégies d'adaptation équitables pour faire face à l'augmentation des températures mondiales reposera sur des informations scientifiques solides et exemptes de biais imposés par les intérêts nationaux et commerciaux. Un examen systématique des méthodes utilisées pour évaluer les stocks de carbone et les variations des stocks de carbone contribuera à l'analyse transparente d'une science complexe et souvent contradictoire. El cambio climático y las altas tasas de emisiones globales de carbono han centrado la atención en la necesidad de sistemas de monitoreo de alta calidad para evaluar cuánto carbono está presente en los sistemas terrestres y cómo cambian con el tiempo. La elección del sistema a adoptar debe guiarse por la buena ciencia. Existe un creciente cuerpo de información científica y técnica sobre los métodos de medición de carbono basados en tierra y de teledetección. La idoneidad y comparabilidad de estos diferentes sistemas no se han evaluado completamente. Una revisión sistemática comparará los métodos de evaluación de las reservas de carbono y los cambios en las reservas de carbono en las categorías clave de uso de la tierra, incluidas las tierras forestales, las tierras de cultivo, los pastizales y los humedales, en los depósitos de carbono terrestre que se pueden contabilizar en virtud del protocolo de Kyoto (biomasa sobre el suelo, biomasa subterránea, madera muerta, basura y carbono del suelo). La evaluación del carbono en los productos de madera recolectada no se considerará en esta revisión. El desarrollo de estrategias de mitigación efectivas para reducir las emisiones de carbono y estrategias de adaptación equitativas para hacer frente al aumento de las temperaturas globales se basará en información científica sólida que esté libre de sesgos impuestos por intereses nacionales y comerciales. Una revisión sistemática de los métodos utilizados para evaluar las reservas de carbono y los cambios en las reservas de carbono contribuirá al análisis transparente de la ciencia compleja y, a menudo, contradictoria. Climate change and high rates of global carbon emissions have focussed attention on the need for high-quality monitoring systems to assess how much carbon is present in terrestrial systems and how these change over time. The choice of system to adopt should be guided by good science. There is a growing body of scientific and technical information on ground-based and remote sensing methods of carbon measurement. The adequacy and comparability of these different systems have not been fully evaluated. A systematic review will compare methods of assessing carbon stocks and carbon stock changes in key land use categories, including, forest land, cropland, grassland, and wetlands, in terrestrial carbon pools that can be accounted for under the Kyoto protocol (above- ground biomass, below-ground biomass, dead wood, litter and soil carbon). Assessing carbon in harvested wood products will not be considered in this review. Developing effective mitigation strategies to reduce carbon emissions and equitable adaptation strategies to cope with increasing global temperatures will rely on robust scientific information that is free from biases imposed by national and commercial interests. A systematic review of the methods used for assessing carbon stocks and carbon stock changes will contribute to the transparent analysis of complex and often contradictory science. ركز تغير المناخ وارتفاع معدلات انبعاثات الكربون العالمية الاهتمام على الحاجة إلى أنظمة مراقبة عالية الجودة لتقييم كمية الكربون الموجودة في الأنظمة الأرضية وكيفية تغيرها بمرور الوقت. يجب أن يسترشد اختيار النظام الذي يجب اعتماده بالعلم الجيد. هناك مجموعة متزايدة من المعلومات العلمية والتقنية حول طرق الاستشعار الأرضي وعن بعد لقياس الكربون. لم يتم تقييم مدى كفاية هذه الأنظمة المختلفة وقابليتها للمقارنة بشكل كامل. ستقارن المراجعة المنهجية طرق تقييم مخزونات الكربون وتغيرات مخزون الكربون في الفئات الرئيسية لاستخدام الأراضي، بما في ذلك أراضي الغابات والأراضي الزراعية والمراعي والأراضي الرطبة، في مجمعات الكربون الأرضية التي يمكن حسابها بموجب بروتوكول كيوتو (الكتلة الحيوية فوق الأرض والكتلة الحيوية تحت الأرض والحطب والقمامة وكربون التربة). لن يتم النظر في تقييم الكربون في منتجات الخشب المقطوع في هذه المراجعة. سيعتمد وضع استراتيجيات تخفيف فعالة للحد من انبعاثات الكربون واستراتيجيات التكيف المنصفة للتعامل مع ارتفاع درجات الحرارة العالمية على معلومات علمية قوية خالية من التحيزات التي تفرضها المصالح الوطنية والتجارية. ستساهم المراجعة المنهجية للطرق المستخدمة لتقييم مخزونات الكربون وتغيرات مخزون الكربون في التحليل الشفاف للعلوم المعقدة والمتناقضة في كثير من الأحيان.