• Energy Research

La biomasse forestière est un indicateur essentiel pour la surveillance des écosystèmes et du climat de la Terre. Il s'agit d'une contribution essentielle à la comptabilisation des gaz à effet de serre, à l'estimation des pertes de carbone et de la dégradation des forêts, à l'évaluation du potentiel des énergies renouvelables et à l'élaboration de politiques d'atténuation du changement climatique telles que REDD+, entre autres. La cartographie mur à mur de la biomasse aérienne (AGB) est maintenant possible avec la télédétection par satellite (RS). Cependant, les méthodes RS nécessitent des données in situ existantes, à jour, fiables, représentatives et comparables pour l'étalonnage et la validation. Nous présentons ici l'initiative Forest Observation System (Fos), une coopération internationale visant à établir et à maintenir une base de données mondiale sur la biomasse forestière in situ. Les estimations de la hauteur de l'AGB et de la canopée avec leurs incertitudes associées sont dérivées à une échelle de 0,25 ha à partir de mesures sur le terrain effectuées dans des parcelles de recherche permanentes à travers les forêts du monde. Toutes les estimations des placettes sont géolocalisées et ont une taille qui permet une comparaison directe avec de nombreuses mesures RS. Le Fos offre le potentiel d'améliorer la précision des produits de la biomasse à base de RS tout en développant de nouvelles synergies entre la RS et les communautés de recherche sur les écosystèmes terrestres. La biomasa forestal es un indicador esencial para monitorear los ecosistemas y el clima de la Tierra. Es un insumo crítico para la contabilidad de gases de efecto invernadero, la estimación de las pérdidas de carbono y la degradación forestal, la evaluación del potencial de energía renovable y para el desarrollo de políticas de mitigación del cambio climático como REDD+, entre otras. El mapeo de pared a pared de la biomasa sobre el suelo (AGB) ahora es posible con la teledetección satelital (RS). Sin embargo, los métodos de RS requieren datos in situ existentes, actualizados, confiables, representativos y comparables para la calibración y validación. Aquí, presentamos la iniciativa del Sistema de Observación Forestal (FOS), una cooperación internacional para establecer y mantener una base de datos global de biomasa forestal in situ. Las estimaciones de altura de AGB y dosel con sus incertidumbres asociadas se derivan a una escala de 0,25 ha a partir de mediciones de campo realizadas en parcelas de investigación permanentes en los bosques del mundo. Todas las estimaciones de parcelas están geolocalizadas y tienen un tamaño que permite la comparación directa con muchas mediciones de RS. El FOS ofrece el potencial de mejorar la precisión de los productos de biomasa basados en RS al tiempo que desarrolla nuevas sinergias entre las comunidades de investigación de ecosistemas basados en RS y en tierra. Forest biomass is an essential indicator for monitoring the Earth's ecosystems and climate. It is a critical input to greenhouse gas accounting, estimation of carbon losses and forest degradation, assessment of renewable energy potential, and for developing climate change mitigation policies such as REDD+, among others. Wall-to-wall mapping of aboveground biomass (AGB) is now possible with satellite remote sensing (RS). However, RS methods require extant, up-to-date, reliable, representative and comparable in situ data for calibration and validation. Here, we present the Forest Observation System (FOS) initiative, an international cooperation to establish and maintain a global in situ forest biomass database. AGB and canopy height estimates with their associated uncertainties are derived at a 0.25 ha scale from field measurements made in permanent research plots across the world's forests. All plot estimates are geolocated and have a size that allows for direct comparison with many RS measurements. The FOS offers the potential to improve the accuracy of RS-based biomass products while developing new synergies between the RS and ground-based ecosystem research communities. الكتلة الحيوية للغابات هي مؤشر أساسي لرصد النظم الإيكولوجية للأرض ومناخها. وهو مدخل حاسم في المحاسبة المتعلقة بغازات الدفيئة، وتقدير خسائر الكربون وتدهور الغابات، وتقييم إمكانات الطاقة المتجددة، ووضع سياسات للتخفيف من آثار تغير المناخ مثل المبادرة المعززة لخفض الانبعاثات الناجمة عن إزالة الغاباتوتدهورها، من بين أمور أخرى. أصبح من الممكن الآن رسم خرائط من الجدار إلى الجدار للكتلة الحيوية فوق الأرض (AGB) باستخدام الاستشعار عن بعد عبر الأقمار الصناعية (RS). ومع ذلك، تتطلب طرق RS بيانات موجودة وحديثة وموثوقة وتمثيلية وقابلة للمقارنة في الموقع للمعايرة والتحقق من الصحة. نقدم هنا مبادرة نظام مراقبة الغابات، وهو تعاون دولي لإنشاء وصيانة قاعدة بيانات عالمية للكتلة الحيوية للغابات في الموقع. يتم اشتقاق تقديرات ارتفاع AGB والمظلة مع أوجه عدم اليقين المرتبطة بها على مقياس 0.25 هكتار من القياسات الميدانية التي تم إجراؤها في قطع البحث الدائمة عبر غابات العالم. جميع تقديرات المخطط محددة جغرافيًا ولها حجم يسمح بالمقارنة المباشرة مع العديد من قياسات RS. يوفر نظام التشغيل الحر إمكانية تحسين دقة منتجات الكتلة الحيوية القائمة على RS مع تطوير أوجه تآزر جديدة بين RS ومجتمعات أبحاث النظام الإيكولوجي الأرضية.

AbstractForest biomass is an essential indicator for monitoring the Earth’s ecosystems and climate. It is a critical input to greenhouse gas accounting, estimation of carbon losses and forest degradation, assessment of renewable energy potential, and for developing climate change mitigation policies such as REDD+, among others. Wall-to-wall mapping of aboveground biomass (AGB) is now possible with satellite remote sensing (RS). However, RS methods require extant, up-to-date, reliable, representative and comparable in situ data for calibration and validation. Here, we present the Forest Observation System (FOS) initiative, an international cooperation to establish and maintain a global in situ forest biomass database. AGB and canopy height estimates with their associated uncertainties are derived at a 0.25 ha scale from field measurements made in permanent research plots across the world’s forests. All plot estimates are geolocated and have a size that allows for direct comparison with many RS measurements. The FOS offers the potential to improve the accuracy of RS-based biomass products while developing new synergies between the RS and ground-based ecosystem research communities.

The accurate prediction of forest above-ground biomass is nowadays key to implementing climate change mitigation policies, such as reducing emissions from deforestation and forest degradation. In this context, the coefficient of determination ($${R^2}$$) is widely used as a means of evaluating the proportion of variance in the dependent variable explained by a model. However, the validity of $${R^2}$$ for comparing observed versus predicted values has been challenged in the presence of bias, for instance in remote sensing predictions of forest biomass. We tested suitable alternatives, e.g. the index of agreement ($$d$$) and the maximal information coefficient ($$MIC$$). Our results show that $$d$$ renders systematically higher values than $${R^2}$$, and may easily lead to regarding as reliable models which included an unrealistic amount of predictors. Results seemed better for $$MIC$$, although $$MIC$$ favoured local clustering of predictions, whether or not they corresponded to the observations. Moreover, $${R^2}$$ was more sensitive to the use of cross-validation than $$d$$ or $$MIC$$, and more robust against overfitted models. Therefore, we discourage the use of statistical measures alternative to $${R^2}$$ for evaluating model predictions versus observed values, at least in the context of assessing the reliability of modelled biomass predictions using remote sensing. For those who consider $$d$$ to be conceptually superior to $${R^2}$$, we suggest using its square $${d^2}$$, in order to be more analogous to $${R^2}$$ and hence facilitate comparison across studies.

The European Union (EU) ensures the conservation of biodiversity through the Natura 2000 Network, which establishes the classification and selection of protected areas at European level. Unfortunately, member countries cannot make the best zoning decisions for biodiversity conservation because there are no clear and uniform parameters to designate Natura 2000 sites. Due to this, it is convenient to evaluate the importance of the criteria for biodiversity conservation through a general assessment, which could establish relevant criteria that can be analysed through geostatistical methods combined in multicriteria analysis. This paper aims to consider biodiversity importance values taking into account land use, so that it is possible to develop a zoning proposal which verifies or corrects the suitability of the designated areas for the Natura 2000 Network in Castilla y León, Andalucía and Madrid (Spain). The choice of these regions allows us to compare areas with a high variability of population density, making possible to compare the potential protected areas with respect to the population living in each area. This assessment has been performed using basic and easily adaptable criteria of biodiversity conservation, so it could be applied in other European territories. In this way, clear and uniform parameters for zoning will be used, being possible to detect the best protected areas. One of the most important purposes of the Natura 2000 Network is to increase connectivity between territories; our work proposes new areas that could be linked to currently protected territories, to favour the achievement of this purpose of the Natura 2000 Network.