Secuestro de carbono en arrozales costeros para la mitigación y adaptación al cambio climático. El delta del ebro como caso de estudio

Resumen

Agriculture has contributed to climate change, which in turn has affected agricultural production. To resolve this situation, agricultural management must adopt measures that jointly meet the challenge of mitigating and adapting to climate change in order to ensure food security. Rice cultivation is important for humans, but its production in coastal areas is threatened by rising sea levels. Paddy rice has great potential to sequester carbon, although with current agronomic practices it produces large amounts of greenhouse gases (GHG), contributing to global warming. The mechanisms involved in carbon sequestration and the determining factors in the emission of greenhouse gases are well known, however, the effective application of farming schemes to optimize carbon sequestration in a territory requires a comprehensive knowledge of its specific conditions. The objective of this PhD Thesis aims to provide insight into the mechanisms influencing soil formation and carbon stabilization in the rice field soil, and to identify crop management measures addressed to improve carbon sequestration and reduce the warming potential in the rice fields, using the Ebro Delta as a study case. For this purpose, three studies were conducted applying complementary analysis methodologies. First, key environmental factors related to soil organic carbon content were analyzed; second, the effect of crop management during post-harvest on GHG emission and carbon balance was evaluated, and third, soil formation associated with inorganic and organic matter was modelled, including carbon sequestration. The results obtained indicate that the carbon content in paddy soils is influenced by the physicochemical characteristics of the soil, such as texture and conductivity, which have a spatial component determined by the marine-fluvial gradient. Regarding the effect of crop management, avoiding post-harvest flooding significantly reduced the global warming potential of the crop without affecting carbon sequestration. Finally, the model simulated paddy soil formation successfully, highlighting that sediment input facilitated vertical accretion in paddy fields, promoting at the same time carbon sequestration. Under the current situation of sea level rise and low sediment input, the simulations indicate that it is essential to restore sediment inputs from the river to the rice fields in order to compensate for sea level rise. This sediment management measure is both an adaptive and mitigation measure, as it would favour vertical accretion, avoid losses in rice production due to soil salinization and promote carbon sequestration. The overall analysis of these results enables an assessment of rice fields' impact on the mitigation capacity of the ecosystems and agro-systems of the Ebro Delta.