Global and Local Effect of Increasing Land Surface Albedo as a Geo-Engineering Adaptation/Mitigation Option: A Case Study of Mediterranean Greenhouse Farming

January 13, 2011 - 12:00pm
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In recent years, there is a growing interest in the design of geo-engineering strategies to offset warming exerted by greenhouse gases through radiative rebalancing of the Earth´s energy budget. The increase of land cover albedo or reflectivity appears as one of the few feasible geo-engineering options. In the case of farmland, greenhouse farming has empirically shown to be effective in warming offset, with a net cooling effect shown in the long term climatic data: this is the case of our recent study on the impact of changes in albedo on the surface air temperatures trends at the biggest concentration of greenhouses in the world - the province of Almeria, in southeast Spain. Here, climatic registry shows a cooling trend of -0.3 ºC/decade in the last 25 years, in an area surrounded by regional warming trends of +0.4 ºC/decade. Nevertheless, many gaps in knowledge and uncertainties remain in this study area, and the net long-term impact on other climate variables still need to be assessed. We have also estimated the carbon footprint of a representative Mediterranean greenhouse production by Life Cycle Assessment (LCA), making the integration of CO2-eq emissions and equivalent “negative emissions” due to albedo effect by the development of high reflective surfaces. We concluded that around 44% of emissions were offset by the albedo effect. However, there remain complex methodological issues when we express shortwave radiative forcing due to albedo change in terms of equivalent reduction in carbon emissions. In the Mediterranean area, the shift from an extensive use towards intensive greenhouse farming has resulted in the concentration of highly profitable farming activities in a limited portion of the territory, with an associated abandonment of low income extensive farming and grazing activities in an area that is around ten times larger. This has boosted a spontaneous recovery of natural vegetation, and allowed the development of forestry plans in the region, with the generation of huge carbon sinks in soils and biomass. These sinks should be accounted for when estimating the net environmental and climatic impact of greenhouse farming, urbanization processes or any intensification of land use. This pattern of land use change been named as “high yield conservation”, has a simple message – Growing more crops per acre leaves more land for Nature. This approach might become one key option for the sustainable use of the available surface of the Earth, as well as a key strategy for adaptation for both human settlements and biodiversity conservation. The narrated slides from this talk are available on Vimeo:

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