Land Use Effects on Climate: Current State, Recent Progress, and Emerging Topics

Abstract

Purpose of Review As demand for food and fiber, but also for negative emissions, brings most of the Earth’s land surface under management, we aim to consolidate the scientific progress of recent years on the climatic effects of global land use change, including land management, and related land cover changes (LULCC). Recent Findings We review the methodological advances in both modeling and observations to capture biogeochemical and biogeophysical LULCC effects and summarize the knowledge on underlying mechanisms and on the strength of their effects. Recent studies have raised or resolved several important questions related to LULCC: How can we derive CO2 fluxes related to LULCC from satellites? Why are uncertainties in LULCC-related GHG fluxes so large? How can we explain that estimates of afforestation/reforestation potentials diverge by an order of magnitude? Can we reconcile the seemingly contradicting results of models and observations concerning the cooling effect of high-latitude deforestation? Summary Major progress has been achieved in understanding the complementarity of modeling, observations, and inventories for estimating the impacts of various LULCC practices on carbon, energy, and water fluxes. Emerging fields are the operationalization of the recently achieved integration of approaches, such as a full greenhouse gas balance of LULCC, mapping of emissions from global models to country-reported emissions data, or model evaluation against local biogeophysical observations. Fundamental challenges remain, however, e.g., in separating anthropogenic from natural land use dynamics and accurately quantifying the first. Recent progress has laid the foundation for future research to integrate the local to global scales at which the various effects act, to create co-benefits between global mitigation, including land-based carbon dioxide removal, and changes in local climate for effective adaptation strategies.

Global Carbon Budget 2021

“…The rising number of pan-tropical or global estimates of carbon stock changes based on satellite remote sensing of carbon densities and forest cover changes (Fan et al, 2019;Qin et al, 2021;Xu et al, 2022;Feng et al, 2022) may seem a promising path for independent evaluation of the land-use emissions term. However, comparison of satellitederived fluxes to global model estimates is hampered for several reasons discussed by Pongratz et al (2021). Most importantly, satellite-based estimates usually do not distinguish between anthropogenic drivers and natural forest cover losses (e.g.…”

“…Lastly, satellite-based fluxes typically quantify committed instead of actual emissions, i.e. legacy CO 2 fluxes from potentially slow processes such as slash, soil carbon or product decay, or forest regrowth are not captured at the time they actually occur but are attributed to the time of the land-use change event (Pongratz et al, 2021). Using data on drivers of forest cover loss to isolate fluxes from agricultural expansion, and looking into gross emissions instead of the net land-use change flux, Feng et al (2022) suggest a stronger increase in global gross emissions (though generally a smaller flux) than the bookkeeping models do (see gross fluxes in Fig.…”

“…Further studies are needed to robustly estimate the trend of global net land-use emissions. Progress is also needed on accurate quantifications of land-use dynamics, including less well observable management types such as shifting cultivation and wood harvesting, and their distinction from natural disturbances (Pongratz et al, 2021).…”

Process-oriented analysis of dominant sources of uncertainty in the land carbon sink

“…. Second, DGVMs are missing carbon losses associated with degraded forests, which can exceed deforestation losses, indicating simulated LULCC losses could be underestimated [40][41][42] . Finally, uncertainty exists with LULCC maps used to drive DGVMs as historical land-use is not perfectly known and products differ in the land cover types and transitions included 40 .…”

Soil Restoration Practices on Priming Effect Intensity and Carbon Fluxes

“…Soil carbon depends on vegetation cover. Any change in land use may signi cantly alter related source or sink characteristics for atmospheric carbon dioxide CO 2 and other GHGs [1,2]. Changes in tropical natural ecosystems are likely to cause reductions in carbon inputs depending on the use, management, physical, chemical, and biological soil [3].…”