Abstract
Abstract. Over the past decade, Brazil has experienced severe droughts across its territory, with important implications for soil moisture dynamics. Soil moisture variability has a direct impact on agriculture, water security and ecosystem services. Nevertheless, there is currently little information on how soil moisture across different biomes responds to drought. In this study, we used satellite soil moisture data from the European Space Agency, from 2009 to 2015, to analyze differences in soil moisture responses to drought for each biome of Brazil: Amazon, Atlantic Forest, Caatinga, Cerrado, Pampa and Pantanal. We found an overall soil moisture decline of −0.5 % yr−1 (p<0.01) at the national level. At the biome level, Caatinga presented the most severe soil moisture decline (−4.4 % yr−1), whereas the Atlantic Forest and Cerrado biomes showed no significant trend. The Amazon biome showed no trend but had a sharp reduction of soil moisture from 2013 to 2015. In contrast, the Pampa and Pantanal biomes presented a positive trend (1.6 % yr−1 and 4.3 % yr−1, respectively). These trends are consistent with vegetation productivity trends across each biome. This information provides insights into drought risk reduction and soil conservation activities to minimize the impact of drought in the most vulnerable biomes. Furthermore, improving our understanding of soil moisture trends during periods of drought is crucial to enhance the national drought early warning system and develop customized strategies for adaptation to climate change in each biome.
Highlights
Drought is a natural and human-induced hazard common to all climate zones in the world (Sheffield and Wood, 2008), generally referred to as a sustained occurrence of belowaverage water availability due to precipitation deficit and soil moisture decline (Magalhães, 2016)
Since we cannot measure in situ soil moisture at high spatial resolution due to logistical constraints, we propose the use of multiple satellite remote sensing sensors as an alternative to obtain drought-relevant information on soil moisture at the national scale
The Caatinga biome had the most Municipal emergency declarations (MEDs) per municipality, followed by the Atlantic Forest, Cerrado, Pampa and Amazon biomes, respectively (Fig. 2)
Summary
Drought is a natural and human-induced hazard common to all climate zones in the world (Sheffield and Wood, 2008), generally referred to as a sustained occurrence of belowaverage water availability due to precipitation deficit and soil moisture decline (Magalhães, 2016). Precipitation deficit is the most studied driver of drought (Mishra and Singh, 2010; Smith, 2013; Villarreal et al, 2016) and has been furthering several drought indicators and models. Precipitation-based indicators are limited in the assessment of social and environmental responses to the lack of rain and not suitable for evaluating the impacts of drought when used alone. Drought indicators based on soil moisture are key to understanding the physical mechanisms of drought and useful for assessing how soil moisture decline can alter vegetation water availability and, agricultural production and ecosystem services (Smith, 2013; NWS, 2006). Lopes Ribeiro et al.: The impact of drought on soil moisture trends across Brazilian biomes
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