Combining UAV thermography, point cloud analysis and machine learning for assessing small‐scale evapotranspiration patterns in a tropical rainforest

Microclimate and vegetation structure control evapotranspiration (ET) from land surfaces at stand and landscape scales. Tropical rainforests are among the most diverse and complex terrestrial ecosystems, harbouring vast plant and animal species throughout their dense multistory canopy. They contribute substantially to global precipitation through their high ET. However, there is little information about ET influences at very small spatial scales under given climatic conditions. In a tropical rainforest on Sumatra, we studied the relationship between pixel‐level ET as derived from high‐resolution (~10 cm), near‐surface thermography from an unmanned aerial vehicle (UAV) and canopy structure as derived from red–green–blue (RGB) image and three‐dimensional (3D) point cloud analyses. The 16 derived potential predictors encompassed vegetation height, height variability, vegetation density and reflectance variables. Using regression models, several of the studied variables had a significant linear relationship with ET, but the explained variance was only marginal. However, applying a random forest algorithm including forward feature selection and target oriented cross validation explained substantial parts of the pixel‐level variance in ET (<jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.56–0.65), thus indicating multiple non‐linear relationships with interactions among predictor variables. Therein, green leaf index, leaf area density and vegetation height were often the most important variables for the prediction outcome, but their sequence varied among the four study plots. Overall, combining canopy structure variables derived from RGB photogrammetry explained relatively large parts of spatial ET variations. Our study thus indicates the large potential of combining UAV‐based thermography and photogrammetry techniques with machine learning approaches to better understand ET but also suggests that more work remains to be done in explaining ET patterns at very small spatial scales

Faire compter les arbres en Afrique: Une meilleure stratégie de MRV de l’agroforesterie pour satisfaire aux ambitions de l’Afrique

Messages clé ◼ L’Action commune de Koronivia pour l’agriculture, adoptée dans le cadre de la CCNUCC, est une opportunité pour faire de l’agroforesterie un élément clé de la réponse africaine aux changements climatiques. ◼ Nous avons évalué la visibilité de l’agroforesterie dans les processus de MRV de la CCNUCC en examinant les communications nationales, les CDN, la documentation REDD+ et les MAAN des pays en développement, en particulier l’ensemble des pays d’Afrique. ◼ L’agroforesterie est plus largement répandue en Afrique que dans toute autre région et de nombreux pays africains entendent l’utiliser pour atteindre leurs objectifs climatiques. Mais en raison d’obstacles techniques et institutionnels, l’agroforesterie est souvent sous-représentée dans les processus de mesure, notification et vérification (MRV) de la CCNUCC. ◼ Le fait que l’agroforesterie échappe souvent aux systèmes nationaux de MRV a des conséquences sérieuses. Ce n’est qu’en mesurant correctement les ressources agroforestières qu’il sera possible de donner au secteur un accès aux sources de financement et autres soutiens, pour faire de l’agroforesterie une pièce centrale de la riposte aux changements climatiques. ◼ Le soutien considérable accordé à l’agroforesterie tend à suggérer qu’en réponse à l’Action commune de Koronivia pour l’agriculture, les pays africains devraient miser sur l’agroforesterie comme stratégie centrale de leur réponse climatique

Hacer que los árboles cuenten en América Latina y el Caribe: Medición, reporte y verificación (MRV) de agroforestería en la CMNUCC

Alrededor de un tercio de los países de América Latina han expresado la intención de utilizar la agroforestería para cumplir con sus compromisos climáticos nacionales. A pesar de este interés, barreras técnicas e institucionales a menudo impiden que la agroforestería sea incluida y tomada en cuenta por los procesos de MRV de la CMNUCC, tales como los inventarios nacionales de gases de efecto invernadero (GEI) y REDD+. ◼ El hecho de que la agroforestería a menudo no sea tomada en cuenta por los sistemas de MRV tiene serias implicaciones. Solo midiendo y reportando adecuadamente los recursos agroforestales, estos podrán obtener acceso a financiamiento y otros tipos de apoyo, logrando que asuman un rol prominente como agentes de respuesta al cambio climático. ◼ Algunos países han encontrado formas de superar estas barreras y hacer notar a la agroforestería en sus sistemas de MRV, proporcionando lecciones que otros pueden seguir

Making trees count in Africa: Improved MRV is needed to meet Africa’s agroforestry ambitions

Key messages ◼ The UNFCCC’s Koronivia Joint Work on Agriculture creates an opening for agroforestry to take on an important role in Africa’s response to climate change. ◼ We reviewed measurement, reporting and verification (MRV) of agroforestry under the United Nations Framework Convention on Climate Change (UNFCCC) by examining national communications, nationally determined contributions (NDCs), REDD+ and Nationally Appropriate Mitigation Actions (NAMAs) in developing countries, including all African nations. ◼ Support for agroforestry was stronger in Africa than any other region, and many African nations plan to use agroforestry to meet climate goals. However, technical and institutional barriers often prevent agroforestry from being represented in UNFCCC MRV processes. ◼ The fact that agroforestry often isn’t counted in national MRV systems has significant implications. Only if agroforestry resources can be properly measured will countries gain access to sources of finance and other support for agroforestry as a response to climate change. ◼ Widespread and strong support for agroforestry suggests that, in responding to the Koronivia Joint Work on Agriculture, African nations should emphasize agroforestry as a central strategy in the continent’s climate change strategies

Making Trees Count in Latin America and the Caribbean: Measurement, reporting and verification (MRV) of agroforestry in the UNFCCC

Key messages ◼ About one-third of countries in Latin America express an intent to use agroforestry to meet national climate commitments. ◼ Despite this interest, technical and institutional barriers often prevent agroforestry from being represented and counted in United Nations Framework Convention on Climate Change (UNFCCC) MRV processes such as national greenhouse gas (GHG) inventories and REDD+. ◼ The fact that agroforestry often isn’t counted in MRV systems has serious implications. Only if agroforestry resources can be properly measured and reported will they gain access to finance and other support, and thereby assume a prominent role as a response to climate change. ◼ Countries in the Americas that have found ways to make agroforestry visible in MRV have coordinated institutional environments, improved technical capacity in land use classification and tracking, and developed programs such as NAMAs to direct attention and resources to the issue

Making trees count in non-Annex I countries: Measurement, reporting and verification (MRV) of agroforestry in the UNFCCC

Key messages ◼ Many developing countries recognize that agroforestry offers benefits for both people and planet and have integrated it into national policy to help meet development and climate goals. ◼ Despite this interest, technical and institutional barriers often prevent trees outside forests and agroforestry from being recognized in United Nations Framework Convention on Climate Change (UNFCCC) measurement, reporting and verification (MRV) processes, such as national greenhouse gas inventories and REDD+. ◼ This lack of inclusion means agroforestry is less likely to receive financial investments and other support to match its potential significance in addressing climate change. ◼ Some countries have found ways to overcome these barriers, providing lessons for others to follow. Successful arrangements include: development of policy and regulations directly addressing agroforestry; farmer and producer groups are involved in the process; there is a collaborative research environment; and coordination among the diverse institutions involved with land use

Making trees count: Measurement and reporting of agroforestry in UNFCCC national communications of non-Annex I countries

Agroforestry—the integration of trees with crops and livestock—generates many benefits directly relevant to the UNFCCC\u27s Koronivia Joint Work on Agriculture, including: (i) building resilience, (ii) increasing soil carbon and improving soil health, (iii) providing fodder and shade for sustainable livestock production and (iv) diversifying human diets and economic opportunities. Despite its significance to the climate agenda, agroforestry may not be included in measurement, reporting and verification (MRV) systems under the UNFCCC. Here we report on a first appraisal of how agroforestry is treated in national MRV systems under the UNFCCC. We examined national communications (NCs) and Nationally Determined Contributions (NDCs) of 147 countries, REDD + strategies and plans of 73 countries, and 283 Nationally Appropriate Mitigation Actions (NAMAs), as well as conducted interviews with representatives of 12 countries in Africa, Asia and Latin America. We found that there is a significant gap between national ambition and national ability to measure and report on agroforestry. Forty percent of the countries assessed explicitly propose agroforestry as a solution in their NDCs, with agroforestry being embraced most widely in Africa (71%) and less broadly in the Americas (34%), Asia (21%) and Oceania (7%). Seven countries proposed 10 agroforestry-based NAMAs. Of 73 developing countries that have REDD + strategies, about 50% identified agroforestry as a way to combat forest decline. Despite these intentions, however, agroforestry is not visible in many MRV systems. For example, although 66% of the countries reported non-forest trees in the national inventory, only 11% gave a quantitative estimate of number of trees or areal extent. Interviews revealed institutional, technical and financial challenges preventing comprehensive, transparent inclusion of agroforestry in MRV systems. The absence has serious implications. If such trees are not counted in inventories or climate change programs, then a major carbon sink is not being accounted for. Only if agroforestry resources are measured, reported and verified will they gain access to finance and other support. We discuss four recommendations to better match ability to ambition

Making trees count: Measurement, reporting and verification of agroforestry under the UNFCCC

About half of developing countries express ambition to use agroforestry—the integration of trees with crops, livestock and other non-forest timber products—for adaptation and mitigation of climate change. In order for agroforestry contributions to be recognized and rewarded, however, countries need reliable systems for measurement, reporting and verification (MRV). Here we review, through key informant interviews and examination of official documents, how agroforestry is addressed in national MRV under the United Nations Framework Convention on Climate Change (UNFCCC). Our review highlights significant gaps between national ambition and national action and capabilities. These gaps are smaller in some countries than in others, but not even one country systematically includes agroforestry in all of its relevant MRV systems. Barriers to the inclusion and explicit representation of agroforestry in MRV systems include: (1) technical barriers, such as exclusion of agroforestry from definitions of land use and lack of access to high-resolution satellite imagery; (2) institutional barriers, such as overlapping or contradictory institutional mandates and lack of human capacity to use available tools; and (3) financial barriers that prevent consistent measurement and inclusive processes. The fact that agroforestry often is not counted in UNFCCC MRV systems has serious implications: If agroforestry trees aren’t counted in MRV systems, then in many ways they don’t count. Only if agroforestry resources are measured, reported and verified will countries gain access to the financial and other support they need to effectively include agroforestry in climate change adaptation and mitigation. Based on emerging lessons, we recommend six ways to support countries to improve MRV of agroforestry

UAV-based thermography reveals spatial and temporal variability of evapotranspiration from a tropical rainforest

Evapotranspiration (ET) from tropical forests plays a significant role in regulating the climate system. Forests are diverse ecosystems, encompass heterogeneous site conditions and experience seasonal fluctuations of rainfall. Our objectives were to quantify ET from a tropical rainforest using high-resolution thermal images and a simple modeling framework. In lowland Sumatra, thermal infrared (TIR) images were taken from an uncrewed aerial vehicle (UAV) of upland and riparian sites during both dry and wet seasons. We predicted ET from land surface temperature data retrieved from the TIR images by applying the DATTUTDUT energy balance model. We further compared the ET estimates to ground-based sap flux measurements for selected trees and assessed the plot-level spatial and temporal variability of ET across sites and seasons. Average ET across sites and seasons was 0.48 mm h–1, which is comparable to ET from a nearby commercial oil palm plantation where this method has been validated against eddy covariance measurements. For given trees, a positive correlation was found between UAV-based ET and tree transpiration derived from ground-based sap flux measurements, thereby corroborating the observed spatial patterns. Evapotranspiration at upland sites was 11% higher than at riparian sites across all seasons. The heterogeneity of ET was lower at upland sites than at riparian sites, and increased from the dry season to the wet season. This seasonally enhanced ET variability can be an effect of local site conditions including partial flooding and diverse responses of tree species to moisture conditions. These results improve our understanding of forest-water interactions in tropical forests and can aid the further development of vegetation-atmosphere models. Further, we found that UAV-based thermography using a simple, energy balance modeling scheme is a promising method for ET assessments of natural (forest) ecosystems, notably in data scarce regions of the world

Carbon Stocks in Miombo Woodlands: Evidence from over 50 Years

Miombo woodlands are extensive dry forest ecosystems in central and southern Africa covering ≈2.7 million km2. Despite their vast expanse and global importance for carbon storage, the long-term carbon stocks and dynamics have been poorly researched. The objective of this paper was to present and summarize the evidence gathered on aboveground carbon (AGC) and soil organic carbon (SOC) stocks of miombo woodlands from the 1960s to mid-2018 through a literature review. We reviewed the data to find out to what extent aboveground carbon and soil organic carbon stocks are found in miombo woodlands and further investigated if are there differences in carbon stocks based on woodland categories (old-growth, disturbed and re-growth). A review protocol was used to identify 56 publications from which quantitative data on AGC and SOC stocks were extracted. We found that the mean AGC in old-growth miombo (45.8 ± 17.8 Mg C ha−1), disturbed miombo (26.7 ± 15 Mg C ha−1), and regrowth miombo (18.8 ± 16.8 Mg C ha−1) differed significantly. Data on rainfall, stand age, and land-use suggested that the variability in aboveground carbon is site-specific, relating to climatic and geographic conditions as well as land-use history. SOC stocks in both old-growth and re-growth miombo were found to vary widely. It must be noted these soil data are provided only for information; they inconsistently refer to varying soil depths and are thus difficult to interpret. The wide range reported suggests a need for further studies which are much more systematic in method and reporting. Other limitations of the dataset include the lack of systematic sampling and lack of data in some countries, viz. Angola and Democratic Republic of the Congo