Drought impacts assessment in Brazil - a remote sensing approach

Climate extremes are becoming more frequent in Brazil; studies project an increase in drought occurrences in many regions of the country. In the south, drought events lead to crop yield losses affecting the value chain and, therefore, the local economy. In the northeast, extended periods of drought lead to potential land degradation, affecting the livelihood and hindering local development. In the southern Amazon, an area that experienced intense land use change (LUC) in the last, the impacts are even more complex, ranging from crop yield loss and forest resilience loss, affecting ecosystem health and putting a threat on the native population traditional way of living. In the studies here we analyzed the drought impacts in these regions during the 2000s, which vary in nature and outcomes. We addressed some of the key problems in each of the three regions: i) for the southern agriculture, we tackled the problem of predicting soybean yield based on within-season remote sensing (RS) data, ii) in the northeast we mapped areas presenting trends of land degradation in the wake of an extended drought and, iii) in southern Amazon, we characterized a complex degradation cycle encompassing LUC, fire occurrence, forest resilience loss, carbon balance, and the interconnectedness of these factors impacting the local climate. Advisor: Brian D. Wardlo

ARIDITY INDEX AND CLIMATIC RISK OF DESERTIFICATION IN THE SEMI-ARID STATE OF SERGIPE

The semi-arid is a region of high temperatures and low rainfall conditions, and can be the gateway to the establishment of climatic processes that aggravate this aridity condition. Therefore, the objective of the present study was to identify the areas most susceptible to desertification in the semi-arid state of Sergipe, through the application of the aridity index. The aridity index was generated from the input monthly data of precipitation and temperature, and the classification of the index was performed in: hyper-arid, arid, semi-arid, sub-humid dry and sub-humid and humid, with a subsequent classification of the risk level as being very high, high and moderate. The semi-arid region of the state of Sergipe has all the superior extension in prominence, since it shows the highest aridity index and, consequently, higher risk to desertification, especially the northwest with a classification of semiarid. Monthly, there is a condition of aridity in some regions, which magnifies the susceptibility to the processes of desertification

Desertification

IPCC SPECIAL REPORT ON CLIMATE CHANGE AND LAND (SRCCL) Chapter 3: Climate Change and Land: An IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystem

Impact of soil moisture on crop yields over Brazilian semiarid

The objective of this work was to investigate the relationship between soil water content and rainfall with rice, beans, cassava and corn yields in the semiarid region of Northeast Brazil. Precipitation and modeled soil water content were compared to yields recorded at the county levels in this region. The results were also integrated over the area of the nine States that lie within the officially recognized region of semiarid climate in Brazil. The influence of water balance components was quantified by calculating their correlation coefficient with yields of the different crop species over the municipalities of the region. It was found that rainfall had higher correlation to crop yields over most of the region, while soil water content had lower values of correlation. This result is consistent with the fact that average root depth is 40 cm, lower than the layer of soil used in the model used to estimate soil water content (100 cm). Plants respond better to the precipitation in the top layers of soil, while the water storage in the deep layer of soil might be important only in other temporal and spatial scales of the hydrological cycle.Peer ReviewedPostprint (published version

Ecological engineering projects increased vegetation cover, production, and biomass in semiarid and subhumid Northern China

Multiple ecological engineering projects have been implemented in semiarid and subhumid Northern China since 1978 with the purpose to combat desertification, control dust storms, and improve vegetation cover. Although a plethora of local studies exist, the effectiveness of these projects has not been studied in a systematic and comprehensive way. Here, we used multiple satellite-based time-series data as well as breakpoint analysis to assess shifts in leaf area index (a proxy for green vegetation cover), gross primary production, and aboveground biomass in Northern China. We documented increased vegetation growth in northwest and southeastern parts of the region, despite drought anomalies as documented by the standardized precipitation-evapotranspiration index during 1982–2016. Significant breakpoints in leaf area index were observed for over 72.5% of the southeastern and northwestern regions, and 70.6% of these breakpoints were detected after 1999, which correspond well to the areas with the highest ecological engineering efforts. Areas with negative trends were mainly located in the Inner Mongolian Plateau, Hulun Biur, Horqin Sand Land, and urban areas. The Loess Plateau had the largest increase in vegetation growth, followed by the north parts of Northern China where biomass increased more in the provinces of Shanxi, Liaoning, Shannxi, Hebei, and Beijing than Xinjiang, Inner Mongolia, Tianjin, and Qinghai. Our results show that multiple ecological engineering projects in the region have increased vegetation cover, production, and aboveground biomass that have led to improved environmental conditions in the study area

Climate change resilient development of family farmers in the brazilian semiarid : an analysis of public policies and of the coexisting with the semiarid paradigm

The Brazilian Semiarid region comprises the poorest people in the country, and one of the two biomes most vulnerable to climate change in Brazil. Public policies have been focused on droughts, but a more organized and articulated civil society in the 1980´s started to seek alternatives to addressing the complex challenges in the region, focusing on more holistic solutions for human coexistence with the Semiarid conditions. This thesis analyses public policies during three historical periods and the civil society-led paradigm Convivência com o Semiárido (CSA, Coexisting with the Semiarid) to verify if they promoted resilience to climate change for family farmers. The research follows a theoretical framework of Social-Ecological Systems and Resilience Thinking, and uses document analysis, fieldwork and interviews. It was found that recent public policies have assisted family farmers to improve living conditions and face droughts impacts, but they have not substantially promoted climate change resilience. Therefore, achievements gained through public policies are at risk, as the changes in climate create new environmental and economic conditions. Concurrently, CSA increases family farmers` climate resilience by applying social technologies through a participatory approach, building local knowledge and promoting the sustainable use of resources. In accordance to resilience theory, CSA is a social process with the potential to drive transformational change, which can be sustained into the future. It only succeeds, however, when several activities are combined. It focuses on civil society rather than the government sphere as pivotal agent of transformation.A região semiárida brasileira abriga a população mais desfavorecida economicamente do país e um dos dois biomas mais vulneráveis às mudanças climáticas no Brasil. Políticas públicas para a região estiveram concentradas nas secas, porém, a sociedade civil começou a buscar alternativas para enfrentar os desafios complexos da região, focada em soluções mais holísticas para a convivência humana com as condições semiáridas a partir da década de 1980. Esta tese analisa as políticas públicas para o semiárido durante três períodos históricos e o paradigma liderado pela sociedade civil, Convivência com o Semiárido (CSA), para verificar se eles promoveram resiliência às mudanças climáticas para os agricultores familiares. A pesquisa segue um quadro teórico de sistemas sócioecológicos e resiliência, e tem como metodologia análise de documentos, trabalho de campo e entrevistas. Os resultados da pesquisa indicam que as políticas públicas recentes contribuíram para a melhoria das condições de vida dos agricultores familiares e enfrentamento dos impactos das secas, mas não promoveram substancialmente resiliência às mudanças climáticas. Portanto, as conquistas obtidas através de políticas públicas estão em risco, uma vez que as mudanças no clima criam novas condições ambientais e econômicas. A CSA aumenta a resiliência climática dos agricultores familiares aplicando tecnologias sociais através de uma abordagem participativa, construindo conhecimento local e promovendo o uso sustentável dos recursos. No entanto, esses resultados apenas aparecem quando várias atividades são combinadas. A CSA foca na sociedade civil e não na esfera governamental como agente fundamental de transformação

Evaluación de la degradación del suelo y sequías en una región árida utilizando índices de sequía, índice de vegetación ajustado al suelo modificado y datos de sensores remotos Landsat

Ain Sefra is part of the Ksour Mountains and it's situated in southwestern Algeria, where the climate is arid. The study area is progressively facing regression and degradation exacerbated by climate change. These trends point to a significant acceleration of desertification and drought and the loss of production systems that play a critical social, ecological, and economic role in the region. To better understand the natural hazard of dryness in Ain Sefra and the impact of climate change, we used various drought indices and remote sensing data. Hence, analyzing precipitation records from 1965 to 2021, through several drought indices, droughts were identified as a recurring phenomenon. Moreover, the frequency of successive dry years is relatively high. There were three most extended continuous dry periods. The first phase lasted seven years from 1980 to 1987, the second twelve years from 1994 to 2006, and the third nine years from 2012 to 2021. Calculation of the Modified Soil-Adjusted Vegetation Index (MSAVI) for five multidate satellite images allowed us to follow the evolution of land use elements in this region from 1977 to 2017. Indeed, the study of these multi-temporal images reveals a considerable growth of sands, moving towards the north and northeast of the zone during the last decades. The combination of drought indices and remote sensing seems to be most promising; whose results are valuable tools for guidance and decision support to local and regional authorities.Ain Sefr, en las montañas Ksour, está situada en el suroeste de Argelia, donde el clima es árido. El área de estudio se enfrenta progresivamente a la regresión y degradación exacerbada por el cambio climático. Estas tendencias apuntan a una aceleración significativa de la desertificación y la sequía y a la pérdida de sistemas de producción que desempeñan un papel social, ecológico y económico crítico en la región. Para comprender mejor el peligro natural de la sequía en Ain Sefra y el impacto del cambio climático, se varios índices de sequía y datos de teledetección. Al analizar los registros de precipitación desde 1965 hasta 2021, a través de varios índices de sequía, se identificaron las sequías como un fenómeno recurrente. Además, la frecuencia de años secos sucesivos es relativamente alta. Hubo tres períodos secos continuos más prolongados. La primera fase duró siete años, de 1980 a 1987, la segunda doce años, de 1994 a 2006, y la tercera nueve años, de 2012 a 2021. El cálculo del Índice de Vegetación Ajustado al Suelo Modificado (MSAVI) para cinco imágenes satelitales multifecha nos permitió seguir la evolución de los elementos de uso del suelo en esta región desde 1977 hasta 2017. De hecho, el estudio de estas imágenes multitemporales revela un crecimiento considerable de arenas, moviéndose hacia el norte y noreste de la zona durante las últimas décadas. La combinación de índices de sequía y sensores remotos parece ser muy prometedores, pues sus resultados son valiosas herramientas de orientación y apoyo a la decisión de los entes locales y regionales.Financial support to perform this study was provided partially by the University Center Salhi Ahmed Naama (Argelia). Antonio Jodar-Abellan acknowledges financial support received form the XTREME Spanish National Project (Ref: PID2019-109381RB-I00/AEI/10.13039/501100011033)

Seasonal sub-basin-scale runoff predictions: A regional hydrometeorological Ensemble Kalman Filter framework using global datasets

Study region The São Francisco River Basin (SFRB) in Brazil Study focus In semi-arid regions, interannual variability of seasonal rainfall and climate change is expected to stress water availability and increase the recurrence and intensity of extreme events such as droughts or floods. Local decision makers therefore need reliable long-term hydro-meteorological forecasts to support the seasonal management of water resources, reservoir operations and agriculture. In this context, an Ensemble Kalman Filter framework is applied to predict sub-basin-scale runoff employing global freely available datasets of reanalysis precipitation (ERA5-Land) as well as bias-corrected and spatially disaggregated seasonal forecasts (SEAS5-BCSD). Runoff is estimated using least squares predictions, exploiting the covariance structures between runoff and precipitation. The performance of the assimilation framework was assessed using different ensemble skill scores. New hydrological insights for the region Our results show that the quality of runoff predictions are closely linked to the performance of the rainfall seasonal predictions and allows skillful predictions up to two months ahead in most sub-basins. The anthropogenic conditions such as in the Western Bahia state, however, must be taken under consideration, since non-stationary runoff time-series have poorer skill as such unnatural variations can not be captured by long-term covariances. In sub-basins which are dominated by little anthropogenic influence, the presented framework provides a promising and easily transferable approach for skillful operational seasonal runoff predictions on sub-basin scale