BG3.14

Recent controversies about the climatic consequences of forestation and deforestation have centered on the carbon storage potential of forests and the local or global thermodynamic impacts due to biogeophysical effects. So far, not much attention has been given to the changes that biogeophysical effects of forestation and deforestation impose on the atmospheric and ocean circulation and consequently on remote weather and climate.  Here we discuss how the changes in the Earth's energy balance following global-scale forestation and deforestation alter the global atmospheric circulation patterns and even have profound effects on the ocean circulation. We perform multicentury coupled climate model simulations in which preindustrial vegetation cover is either completely forested or deforested and carbon dioxide mixing ratio is kept constant. Forestation leads to global warming of +0.5 K, which is most pronounced over northern extratropical land. Consequently, the meridional heat transport in the Northern Hemisphere decreases in the forestation simulation. The reduction mainly occurs in the ocean as a result of a weakened Atlantic meridional overturning circulation (AMOC). Extratropical land-warming results further in weaker and poleward shifted weather systems, which, via momentum feedback to the mean flow leads to an attenuation and poleward displacement of the extratropical jet stream. Deforestation leads to global cooling of -1.6 K, a stronger AMOC and extratropical jet stream, a southward shift of the intertropical convergence zone and a stronger Hadley cell in boreal winter, and a weaker Hadley cell in boreal summer. In many aspects, deforestation causes the reverse patterns compared to forestation but with larger amplitudes. These larger amplitudes are mostly related to a strong snow-ice-albedo feedback in high latitudes. Both land surface changes substantially affect regional precipitation, temperature, and surface wind patterns across the globe. The design process of large-scale forestation projects thus needs to take into account global circulation adjustments and their influence on remote climate.

How to cite: Portmann, R., Beyerle, U., Davin, E., Fischer, E., De Hertog, S., and Schemm, S.: Changes to the Earth’s energy budget due to global forestation and deforestation affect remote climate via adjusted atmosphere and ocean circulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1815, https://doi.org/10.5194/egusphere-egu22-1815, 2022.

Land use/cover change is central to understanding the global sustainability challenges of climate change, biodiversity loss, and food security. Yet, while the magnitude of global land use has often been studied, little is known about land use transitions and their drivers, and how these vary across the world. A major obstacle has been the lack of consistent long-term data with sufficiently high resolution.
Here we analyse the drivers of major global land use transitions based on a novel high-resolution land use reconstruction, HILDA+ (Historic Land Dynamics Assessment+). We (1) identify key land use transitions and their spatiotemporal patterns and (2) correlate national time series of annual land use transitions with a range of influencing variables that represent indirect drivers (demography, politics and economics) and direct drivers (production and environment) across the globe.
We identify 12 major land use transitions and find that agricultural expansion accounted for the largest share of global land use change (~7.6 million km²), an area as large as Greece every year between 1960 and 2019. A major portion of this land is made up of pasture/rangeland expansion, mainly used for nomadic pastoralism. Areas of cropland expansion are mainly located in the Global South, particularly in South America (Argentina, Brazil), Africa (Ethiopia, Nigeria, Uganda), India and Thailand. Here we notice a shift of agricultural expansion from South America to Africa since the late 1980s. Globally, forest loss (~3.6 million km²), including deforestation for pasture/rangelands or cropland and forest degradation to shrub/grassland, outweighed forest expansion (~2.6 million km²) during 1960-2019. Whereas forestry, crop-pasture dynamics and cropland abandonment dominated in the Global North, deforestation, forest degradation and agricultural expansion are major transitions of the Global South.
Our driver analysis reveals that economic factors are the largest indirect drivers of global land use transitions in terms of area (~6.7 million km²). Of these, Gross Domestic Production (GDP) is the strongest driver in the Global North, mainly for forest expansion, forestry and urban growth. In contrast, wage and cereal price lead the list in the South, mostly related to agricultural expansion. Indirect-direct driver combinations of economy with production (~4.7 million km²), politics with production (~3.2 million km²) and demography with production (~2.3 million km²) affected the largest areas. We find that environmental indicators have a greater influence on land use change in the South, related to deforestation or desertification, than in the North, linked to crop-pasture dynamics. Indirect drivers show higher correlations than direct drivers, which underlines the importance of social systems on the extent and speed of land use change.
Giving new data-driven and quantitative insights into a largely untouched field, we reveal the importance of indirect drivers from economy, politics and demography for land use transitions across the globe. Learning from the recent past, understanding how socio-economic and environmental factors affect the way humans use the land surface is essential for estimating impacts of land use change and implementing measures of climate mitigation and sustainable land use policies. With our findings, we can make a contribution to this.

How to cite: Winkler, K., Fuchs, R., Rounsevell, M., and Herold, M.: Global land use transitions and their drivers during 1960-2019, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9145, https://doi.org/10.5194/egusphere-egu22-9145, 2022.

Drought is a complex climatic hazard with major impacts on both human and natural system. It is very likely leading to agricultural loss, forest mortality and drinking water scarcity. In recent years, the occurrence frequency and intensity of droughts has been increasing within a warming climate. This poses serious threats to future food security, ecosystem (e.g., changing the forest structure and carbon content) and fresh water stress for small islands. Precipitation, temperature and other atmospheric factors have an influence on the drought conditions. Furthermore, the impact of land cover change on climate mostly on precipitation and temperature has been established in previous studies. To our best knowledge, the effect of change in land cover, especially in large forest cover, on droughts is largely unexplored. This, however, is important to understand the impact of land cover on climate variability and the sensitivity of the droughts to changes in the climate. This study aims at quantifying the effect of forest cover change and changing meteorological factors  on long-term and short-term droughts across four different climate regions (i.e. equatorial, arid, temperate and snow region).

We analyse the influence of forest cover changes to droughts. Meteorological data (precipitation and temperature), land cover dataset, and drought indices (the Palmer Drought Severity Index and the Standardized Precipitation Evapotranspiration Index) for almost 30 years are used to study the influence of forest cover fraction variability on droughts for different time scales and across different climate zones. Linear model and analysis of variance (ANOVA) have been used in the analysis to explore how forest cover changes impact on the drought occurrence frequency and intensity. Our findings can be used in making policy decision involved in forest management and water resource planning. 

How to cite: Li, Y. and Rust, H. W.: Assessment of drought index response to changes in forest cover across different climate zones, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3518, https://doi.org/10.5194/egusphere-egu22-3518, 2022.

Recent observation-based and modelling studies have highlighted the impacts of irrigation on near-surface climate, and it has been stressed that irrigation can alleviate hot extremes, change precipitation patterns and increase air moisture. However, most of the previous studies only focused on historical periods, while potential climate change, land cover conversions and irrigation method advances may alter both the magnitudes and patterns of irrigation-induced effects, thus the influence of irrigation in the future remains uncertain. To address this question, we will employ version 2 of the Community Earth System Model (CESM2) with an updated irrigation scheme considering different irrigation techniques, to detect the impacts of irrigation on near-surface climate under different future scenarios. To include the influence of climate, land cover and irrigation method, several Representative Concentration Pathways (RCP) and Shared Socio-economic Pathways (SSP) scenarios will be selected, and different scenarios of Irrigation Method Distribution (IMD) evolvement will be designed in line with SSP scenarios for this study. Different combinations of RCP, SSP and IMD scenarios will be used to force the model, and the outputs of these experiments will be analysed and compared. We anticipate that our results will reveal how irrigation-induced impacts on near-surface climate will evolve under different scenarios.

How to cite: Yao, Y. and Thiery, W.: Evolvement of irrigation-induced impacts on near-surface climate under future scenarios, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1465, https://doi.org/10.5194/egusphere-egu22-1465, 2022.

Blue-Green Infrastructure (BGI) is a framing concept concerning the connectivity of ecosystems, founded on nature-based solutions and a multi-functionality approach, which includes contributions by nature to disaster risk reduction, infrastructure resilience, erosion control, land formation, and other ecosystem services (World Risk Report, 2012). The study reviews the potential of areas of BGI to mitigate climate change (EEA Report, 2009) and produces maps showing fragmentation areas along the Estonian coast using UAVs and satellite imagery. This allows a more detailed and objective evaluation of the indicators of the conservation state and potential improvement of future connectivity between BGI elements, ensuring coverage of appropriate protection status for coastal habitats. Reliable estimation and understanding of the ecological integrity of habitats and species on the effectiveness of the Natura 2000 network, including analysis of valuable coastal areas to define missing indicators and formulate essential markers for its resilience in Estonia. A disconnected series of inefficiently managed natural components produce far fewer public benefits than they have the potential for.

A comprehensive study of the Estonian coastal zone is based on Estonian legislation, Integrated Coastal Zone Management, the CORINE Land Cover (CLC) system, natural protected areas (NPA), the Estonian Green Network, Agricultural Registers, and Information Board (ARIB), Natura 2000, and benthic habitats datasets that apply to land use regulation in the development planning process to identify the appropriate intensity of land-use and conflicts of interest to be resolved. National BGI strategies, either independently or integrated into broader national policies, identify blue and green assets, corridors, and areas of particular importance outside protected areas that would help the policy instruments. Estonia has been actively planning a blue-green infrastructure approach since 1983, at least in the ecological network sense on a national level, and elaborates the model into a comprehensive plan and implementation program.

How to cite: Kaskevich, V., Villoslada Peciña, M., Ward, R., and Sepp, K.: Mapping Blue-Green infrastructure to evaluate conditions in the Estonian coastal zone, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1739, https://doi.org/10.5194/egusphere-egu22-1739, 2022.

The Alps are experiencing large climatic and socio-economic changes. Climate change is leading to an above-average increase in temperatures and subsequent changes in the timing and duration of snow cover. In parallel, socio-economic changes are affecting land use in the Alpine region. Both, snow cover duration/timing and land use changes directly affect the surface albedo of this landscape and therefore the energy balance of this region. Globally, changes in surface albedo due to land use changes and changes in snow/ice cover affect surface albedo, and thus radiative forcing, in opposite directions.
In this study, we investigated the impact of four different future land use scenarios, 12 future snow cover scenarios on the surface albedo in the alpine region of South Tyrol (Italy) in the year 2100 compared to conditions in 2010. Both, the individual effects of changes in land use and future snow cover patterns were investigated, as well as the interactive effects of these two processes.
The hypothetical changes in albedo until 2100 associated with changes in land and/or snow cover were assessed by establishing a surface albedo model based on remotely sensed albedo (MODIS MCD43A1), snow cover data (MODIS MOD10A1), land cover data, as well as geographical information (ASTER ASTGTM).  Potential future land covers were developed on the basis of likely socio-economic pathways and their spatial distribution was mapped. Snow cover scenarios for 2100 are based on EURO CORDEX RCP 2.6 and 8.5 climate scenarios.
Snow cover was by far the most important predictor for albedo, followed by the occurrence of needle leaf forests using a regression tree algorithm. This algorithm exhibited excellent skill in modelling current albedo conditions based on the above-mentioned predictors.
Likely future snow cover conditions lead to a decrease in average albedo, the magnitude of which depended on the chosen RCP and combination of global/regional climate model. Likely future land cover scenarios caused changes in spatially averaged albedo of the study domain in the same order of magnitude like the RCP 2.6 snow cover scenarios. Simulations with factorial combinations of land cover and snow cover scenarios showed the compounding effect of these two processes. 

How to cite: Hammerle, A., Tasser, E., Matiu, M., and Wohlfahrt, G.: Albedo-mediated interactive effects of land- and snow cover changes on the radiative forcing in Northern Italy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12746, https://doi.org/10.5194/egusphere-egu22-12746, 2022.

The effect of municipal solid waste landfills over the surrounding environment is often understood to be highly critical, even greatly modifying the existing land use. However, objective evaluations of this environmental impcts are seldom being performed. This work shows results obtained when evaluating the land use change induced by MSW landfills applying the Weighted Environmental index (WEI). WEI is based on the use of GIS techniques accounting for different information sources (digital cartography, aerial photographs and satellite images). WEI assigns environmental values to land use based on the degree of anthropogenic intervention and its occupation surface.

A georeferenced multitemporal statistical analysis is performed considering the values of WEI previously assigned to every land use. The methodology has been applied to analyze the land use change near all the existing MSW landfills in operation of Valencia Region (Spain).  Data have been obtained from the Spanish Land Occupation Information System (SIOSE) public database and integrate the more recent GIS information about land use/land cover. 

How to cite: Rodrigo-Ilarri, J., Rodrigo-Clavero, M.-E., Romero, C. P., and Suárez-Romero, P.: Do solid waste landfills really decrease the environmental value? The case of the Valencia Region (Spain), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6264, https://doi.org/10.5194/egusphere-egu22-6264, 2022.

Land management and anthropogenic land cover change (LMLCC) plays a key role in the global carbon budget. For example, approximately half of the terrestrial biomass has been removed by LMLCC to date. Conversely, large potentials for carbon dioxide removal are invoked when vegetation-based negative emission technologies such as afforestation are discussed. Previous studies on LMLCC effects on the carbon cycle focused on the direct effect of tree removal or regrowth on carbon fluxes. However, a suite of studies has shown that LMLCC has an important influence on climate via biogeophysical effects through changes in energy and water fluxes. This influence can reach far beyond the location of LMLCC, called the "nonlocal effect" of LMLCC on climate. This raises the question if LMLCC can also have non-negligible effects on the carbon cycle remote from the LMLCC location itself. Our study establishes the concept how to investigate strength and patterns of the unintended nonlocal side-effects of LMLCC on carbon stocks and fluxes.

Therefore, we conducted three different fully-coupled atmosphere-ocean-land experiments of idealized global cropland expansion with and without cropland irrigation as well as global re-/afforestation starting from today's state over a 150-year period under present day solar and trace gas forcing. All experiments were simulated by three different earth system models (MPI-ESM, EC-EARTH and CESM) to additionally quantify inter-model uncertainty and potentially uncover specific model biases. Here only CESM and MPI-ESM results are presented. To separate the local and nonlocal effects we use a checkerboard approach of grid boxes with and without LMLCC as proposed by Winckler et al., 2017. That is, we separate the carbon stock changes due to LMLCC at the location of LMLCC (local effect) from those induced by climate change caused by remote LMLCC (nonlocal effect). The total effect is the sum of both, the local and nonlocal effect.

The results of MPI-ESM (CESM) show that the global nonlocal effect on vegetation carbon (cVeg) accounts for 6% (3%) and 4% (0.6%) of total cVeg changes for crop expansion and afforestation simulation, respectively. Additionally, applying irrigation to crop expansion strongly increases the nonlocal climate induced cVeg change by 52% (610%) of total cVeg change for MPI-ESM (CESM).  The nonlocal effect of regions with largest carbon changes exhibit partly much larger nonlocal/total ratio. For instance, the nonlocal cVeg change in the Congo basin after cropland expansion accounts for more than 30% of total cVeg change. Furthermore, in some regions, the nonlocal effect of cVeg can be opposite to the local effect, and may thus reduce the total effect of the LMLCC practice compared to what would be expected from the local effect alone.

Overall, the results from MPI-ESM and CESM indicate that the nonlocal carbon effect is important in key regions and can even become globally important for the irrigation practices. In addition to local effects, these unintended nonlocal effects need to be considered when the impacts of a LMLCC practice on the entire carbon cycle (e.g., also with regard to a potential carbon dioxide removal method) will be assessed.

How to cite: Guo, S., Havermann, F., De Hertog, S., Thiery, W., Luo, F., Manola, I., Coumou, D., Lejeune, Q., Schleussner, C.-F., and Pongratz, J.: Simulated unintended biogeochemical effects of idealized land cover and land management changes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11533, https://doi.org/10.5194/egusphere-egu22-11533, 2022.