Proposal for scientifically based time aspects to bridge dLUC carbon footprint with current carbon accounting standards

Main Presenter:    Miguel Montero Alonso 

Co-Authors:   Miguel Brandão     Jorge Blanco Cejas      Jovita Moreno Vozmediano                                    

Original global forest cover has declined sharply in recent decades, a key indicator of transgression of the land-system change planetary boundary (Richardson, 2023). Given the increased attention to planetary boundaries in IPCC AR6, we propose a science-based alternative to the conventional 20-year amortization used to annualize land-use-change (LUC) emissions. This update is justified based on that most of global land use change from 1960 took place in the 90s’ decade and early 00s’.

To better understand dLUC modelling and data needs we conduct a literature review. It shows that top-down approach derived from statistics is used as gross validation whereas bottom-up data are more refined but more difficult to obtain. dLUC data reliability is key to correctly account carbon footprint since it strongly varies depending on the models and data used. For example (Batista, 2025) work on agricultural land in Brazil reveal that dLUC emissions are highly heterogeneous across municipalities and land uses. Nevertheless, these studies lack comprehensive sensitivity analyses for specific variables used in PAS 2050:2012.

We focus on PAS 2050:2012 dLUC accounting because it underpins widely used standards (e.g., PEF, GHG Protocol). Using traceable open data (FAO, Global Forest Watch), available from early 90s’, and IPCC carbon-stock guidance, we implement alternative time aspects (Gonçalves Maciel, 2022) and group them into three scenarios to test the effect of different inventory and amortization periods. Two scenarios with same 20-year amortization period (AP) while the inventory period (IP) varies from 1990-2010 and 2002-2022 to assess the influence of IP in dLUC. The third scenario covers 1990-2022 to better understand if cumulative dLUC emissions always increase for longer AP and if the same principle applies for the annualized values. This is, considering PAS 2012:2050 modelling features.

We conduct uncertainty and sensitivity analyses across selected crop–country case studies, varying key PAS 2050 drivers (land-area expansion/contraction shares and crop yield). Preliminary results show that PAS 2050 outcomes are highly sensitive to both temporal framing and cropland dynamics: annualized dLUC emissions differ markedly across scenarios within same crop. For example: soybean annualized emissions in Brazil (>70%) or for cumulative palm oil dLUC emissions in Indonesia (>30%). We provide a PAS 2050:2012-compliant automated Excel calculator and open Python code for uncertainty/sensitivity analysis, enabling practitioners to test additional crops and reduce “orphan” emissions outside the conventional 20-year window while remaining implementable in LCA inventories

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