A study conducted by Técnico researchers and published in the journal Sustainability points out some ways to mitigate climate change by improving Portugal’s agricultural soils. The study titled “Estimating Soil Carbon Sequestration Potential in Portuguese Agricultural Soils Through Land-Management and Land-Use Changes”, has revealed that improving degraded pastures has the greatest sequestration potential, representing around 4% of Portugal’s total greenhouse gas (GHG) emissions in 2021.
“Quantifying the GHG mitigation potential associated with pasture improvement is very important to help us understand and think about the various possible ways to mitigate climate change in Portugal. We can use a multitude of mitigating practices, and this could be one of them”, explains Mariana Raposo, a researcher at Técnico and at the Marine, Environment and Technology Center (MARETEC), and the lead author of the study. In addition to this theoretical potential, there is also the study of other issues that could affect the application of these changes in land use, “such as questions of financial incentives for farmers to make these improvements”.
The study estimated the mitigation capacity of various land-use and land-management changes. The practices and land-use conversions analysed include, among others, no-till farming, the conversion of annual crops to intensive permanent, the improvement of degraded pastures, and the abandonment of both permanent and annual crops, covering more than 7,000 unique agricultural sites across mainland Portugal. “When applied to all potentially available areas, the improvement of degraded pastures has the greatest sequestration potential at national level”, she explains.
For the first time in Portugal, this study applied the ‘tier 1’ methodology (a methodology described and made available by the Intergovernmental Panel on Climate Change (IPCC), which includes equations and predetermined emission factors for different climates and soil types) to estimate the sequestration potential of 7,000 agricultural points from the LUCAS network – a 2x2km georeferenced network of points in Europe – and combined it with data from agricultural areas managed for various crops. ‘In our study, we used this already georeferenced network of points and cross-referenced it with land use data in Portugal. This process resulted in a network of points that only includes agricultural areas under exploitation (annual crops, pastures, and permanent crops),’ explains Mariana.
Another conclusion of the study is that converting annual crops to permanent crops in the Baixo Alentejo and Alentejo Litoral regions – such as the process underway with the planting of almond trees in these regions – could lead to significant carbon losses, which means that it will not be a beneficial strategy (unlike improving pastures) for reducing GHG emissions.
The study is authored by Mariana Raposo and Tiago Domingos (Técnico / MARETEC) and Paulo Canaveira (Técnico / MARETEC / Instituto Superior de Agronomia / LEAF).
