Historical Land Cover Change Research Articles

Flood Hazard Mapping of a Rapidly Urbanizing City in the Foothills (Birendranagar, Surkhet) of Nepal

Flooding in the rapidly urbanizing city of Birendranagar, Nepal has been intensifying, culminating in massive loss of life and property during July and August 2014. No previous studies have monitored underlying land-cover dynamics and flood hazards for the area. This study described spatiotemporal urbanization dynamics and associated land-use/land-cover (LULC) changes of the city using Landsat imagery classifications for five periods between 1989 and 2016 (1989–1996, 1996–2001, 2001–2011, 2011–2016). Areas with high flood-hazard risk were also identified on the basis of field surveys, literature, and the Landsat analysis. The major LULC changes observed were the rapid expansion of urban cover and the gradual decline of cultivated lands. The urban area expanded nearly by 700%, from 85 ha in 1989 to 656 ha in 2016, with an average annual growth rate of 23.99%. Cultivated land declined simultaneously by 12%, from 7005 ha to 6205 ha. The loss of forest cover also contributed significantly to increased flood hazard. Steep topography, excessive land utilization, fragile physiographic structure, and intense monsoonal precipitation aggravate hazards locally. As in Nepal generally, the sustainable development of the Birendranagar area has been jeopardized by a disregard for integrated flood-hazard mapping, accounting for historical land-cover changes. This study provides essential input information for improved urban-area planning in this regard.

Land-Cover Change Analysis and Simulation in Conakry (Guinea), Using Hybrid Cellular-Automata and Markov Model

In this study, land-cover change in the capital Conakry of Guinea was simulated using the integrated Cellular Automata and Markov model (CA-Markov) in the Geographic Information System (GIS) and Remote Sensing (RS). Historical land-cover change information was derived from 1986, 2000 and 2016 Landsat data. Using the land-cover change maps of 1986 and 2000, the land-cover change map for 2016 was simulated based on the Markov model in IDRISSI software (Clark University, Worcester, MA, USA). The simulated result was compared with the 2016 land-cover map for validation using the Relative Operating Characteristic (ROC). The ROC result showed a very strong agreement between the two maps. From this result, the land-cover change map for 2025 was simulated using CA-Markov model. The result has indicated that the proportion of the urban area was 49% in 2016, and it is expected to increase to 52% by 2025, while vegetation will decrease from 35% in 2016 to 32% in 2025. This study suggests that the rapid land-cover change has been led by both rapid population growth and extreme poverty in rural areas, which will result in migration into Conakry. The results of this study will provide bases for assessing the sustainability and the management of the urban area and for taking actions to mitigate the degradation of the urban environment.

Inconsistent Responses of Hot Extremes to Historical Land Use and Cover Change Among the Selected CMIP5 Models

AbstractLand use and cover change (LUCC) is an important anthropogenic forcing of the climate system. Previous studies have demonstrated that LUCC significantly impacts both mean and extreme temperatures. In this study, we explored the multimodel performance of simulating LUCC‐induced asymmetric effects on the different percentiles of maximum temperatures (Tmax) as well as the possible reasons for these effects using results from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Four state‐of‐art Earth system models (which provide the necessary data) are selected for investigating this issue. In general, all the cases of the model from the Geophysical Fluid Dynamics Laboratory show robust asymmetric responses between the 90th (TX90P) and 10th percentiles (TX10P) of Tmax, mainly due to cropland expansions, especially over India, the Sahel, and some parts of North America. However, weak and insignificant responses are shown for both the TX90P and TX10P in other models. The different changes in the Tmax variability among the models are primarily responsible for the occurrence of asymmetric features. Furthermore, by decomposing the Tmax changes over three typical regions, we analyze the potential causes for the inconsistencies among these models' results and find two crucial processes, that is, the repartitioning of the turbulent heat fluxes and the changes of the diurnal cycle variability due to LUCC. Whether these processes are pronounced determines the occurrence of the asymmetric Tmax responses. Overall, this study provides a critical clue for reducing the uncertainties of the LUCC effects on temperature extremes, which should be evaluated against observations.

Hydrologic impacts of changing land use and climate in the Veneto lowlands of Italy

Abstract The Po valley in northern Italy is one of Europe’s largest and most anthropogenically-modified lowland areas, where intensifying climate and land transformation are increasingly causing water management problems. In this study, the Wageningen Lowland Runoff Simulator (WALRUS) is calibrated, validated, and applied to a reclaimed basin in the Veneto region (Italy) in order to assess the hydrologic impacts of land use and climate change scenarios. First-time model calibration for Mediterranean lowlands resulted in reasonable performance during the training year (NSE 0.77), but lower validation performance (NSE 0.53), while potential for improved calibration was limited by data availability. Scenario analysis covers the historical and future changes in land cover and climate throughout a century (1951–2060), based on aerial imagery analysis, hydrologic measurements, COSMO-CLM regional climate projections and demographics. WALRUS simulations illustrate how land use transformation (i.e. expanded built-up zones and a diminished drainage network) have a strong potential to increase discharge intensities from the catchment, mostly evident in summer peak flow (past −34%; future +48%). A historical scenario of combined land use and climate shows even stronger deviations from the present (annual discharge −19%; summer peak flow −45%), resulting from an observed increase in rainfall intensity and seasonality over the past 50 years. With drier future climate projections, however, the discharge response is moderate in the combined future scenario. Despite the non-optimal model calibration, the presented work in the Veneto region illustrates the directional impact of processes typical of anthropogenic lowlands. Particularly, the impact of observed land transformation seems to diminish the buffering and storage capacity of the catchment, thereby enhancing the hydrologic risks in modern times.

Landscape changes in a 19th century wood pasture and grazing forest

The Bukk Mountains were covered by continuous forests even in the 18th century. First plans for exploitation originate from the late 1700’s; thus, this is the time when planned forest management in the Bukk Mountains started. Our aim is to shed light on land use and historical land cover changes of the grazing forest and wood pasture on the Magas Hill Forest (Ozd–Egercsehi Basin, NE-Hungary) since the 18th century, describe its current state (based on ethnographical data, maps, and field research), and give suggestions on its reconstruction and conservation management. The hills around Egercsehi and Mikofalva villages were once covered by 808.5 ha continuous grazing forest. This forest has almost totally disappeared, and one-time oak forests show no continuity with today’s black locust stands, despite for a 35.3-ha patch in the southern slope of Magas Hill. This remnant is a various mosaic of closed forest, degraded grazing forest, wood pasture, clearing, and grassland, with old (150–200 year) veteran trees. As a consequence of no management (abandonment of forest grazing), original vegetation has almost totally been abolished by invasive alien species. Area of mowed, open grassland is 5.3 ha, while 20.1 ha commemorates on the one-time wood pasture, the remaining is shrubby (spontaneously) with afforestation. The area is not listed in the Hungarian cadastre of wood pastures. This register lists 6 wood pastures in Heves County; this current one is the 7th. The unique stand of veteran trees is still visible and the process of scrub encroachment might by stopped by adequate management, therefore, valuable habitats can be conserved. In favour of reconstruction of the wood pasture – grazing forest mosaic and maintenance of the desirable state, we suggest beef and sheep grazing, combined with mowing, depending on the state of afforestation.

Development of a cellular automata model using open source technologies for monitoring urbanisation in the global south: The case of Maputo, Mozambique

Cities throughout the world are expanding, and globally we are witnessing a significant amount of urbanisation. Currently, 54% of the world's population lives in cities, and an increase of 66% is expected by 2050. Based on the World Urbanisation Prospects' report, most of this growth is projected to concentrate in Asia and Africa. The resulting uncontrolled urbanisation can lead to many issues with profound impacts on health, poverty, and social inequality. Monitoring our global landscapes in the most rapidly growing regions particularly in the global south becomes thus an important endeavour. The estimation of future urban patterns become thus part of important topics that foresight the necessary support systems that efficiently cope with the carrying capacity of these urban regions. In this sense, this paper aims to i) monitor historical land cover changes in one of such major cities - Maputo, Mozambique, and, ii) project future patterns of urban fabric in its metropolitan region. To achieve this, satellite imagery from Landsat between 2000 and 2015 was collected and classified using a maximum likelihood algorithm. Spatiotemporal monitoring of urban settlements showed that within the proposed temporal scope, massive urban development took place while depleting a substantial amount of other land use types. Based on this spatiotemporal cognisance, a customized cellular automaton (CA) model was built that embeds the trends of changes while predicting future patterns. Our predictions exposed a significant amount of urbanisation will evolve over the next years if no significant controlling mechanism to cope with rapid urbanisation is integrated. Our findings, as well as conclusions, aim to aid local urban planners and policy makers in the course of urban planning in the region while taking advantage of novel open source methodologies that offer cost reduction and enable efficient monitoring for large urban extents.

Land use and land cover dynamics in Dendi-Jeldu hilly-mountainous areas in the central Ethiopian highlands

The central Ethiopian highlands where most human and livestock populations concentrated have experienced a drastic change in land use and land cover (LULC) of the landscapes. This study was aimed to define the rate and pattern of LULC changes in Dendi-Jeldu hilly-mountainous areas in the central Ethiopia. Aerial photographs of years 1957 and 1995, and Landsat images taken at 1995 and 2014 were used to analyze the historical land use and land cover (LULC) changes. The study covered an area of about 438km2. The analysis extracted from these remote sensing data revealed that, in 1957, the dominant LULCs were pastureland, cultivated land (cropland) and forestland covering 49, 25 and 20% of the total area, respectively. Remarkable LULC change dominated by cultivated land expansion (now covering 68% of the total area), however, claimed vast areas under pastureland (main), forestland and woodland. Deforestation in particular, would have been greater if Chilimo forest (remnant afro-montane forest) was not under state control. Plantation forestry exclusively dominated by eucalyptus species also showed substantial expansion into pastureland in the period between 1957 and 1995, and cultivated land between 1995 and 2014. In the period 1957 to 2014 cultivated land, plantation land and settlement were increased by 170%, 13,674% and 172% respectively, while pastureland, forestland and woodland declined by 67%, 73% and 100%, respectively. Change from natural habitat (pastureland, forestland and woodland) to other land uses (cultivated, plantation and settlement lands) is likely to have a large impact on biodiversity, land degradation and beyond.

Land-Surface Characteristics and Climate in West Africa: Models’ Biases and Impacts of Historical Anthropogenically-Induced Deforestation

Land Use Land-Cover Change (LULCC), such as deforestation, affects the climate system and land-atmosphere interactions. Using simulations carried out within the LUCID (Land Use and Climate, IDentification of robust Impacts) project framework, we first quantify the role of historical land-cover change induced by human activities on surface climate in West Africa. Focusing on two contrasted African regions, we find that climate responses of land-use changes are small but they are still statistically significant. In Western Sahel, a statistically significant near-surface atmospheric cooling and a decrease in water recycling are simulated in summer in response to LULCC. Over the Guinean zone, models simulate a significant decrease in precipitation and water recycling in autumn in response to LULCC. This signal is comparable in magnitude with the effect induced by the increase in greenhouse gases. Simulated climate changes due to historical LULCC could however be underestimated because: (i) the prescribed LULCC can be underestimated in those regions; (ii) the climate models underestimate the coupling strength between West African surface climate and leaf area index (LAI) and (iii) the lack of interactive LAI in some models. Finally, our study reveals indirect atmospheric processes triggered by LULCC. Over the Western Sahel, models reveal that a significant decrease in solar reflection tend to cool down the surface and thus counteract the atmospheric feedback. Conversely, over the Guinea zone, models reveal that the indirect atmospheric processes and turbulent heat fluxes dominate the climatic responses over the direct effects of LULCC.

The role of protected areas in land use/land cover change and the carbon cycle in the conterminous United States.

Protected areas (PAs) cover about 22% of the conterminous United States. Understanding their role on historical land use and land cover change (LULCC) and on the carbon cycle is essential to provide guidance for environmental policies. In this study, we compiled historical LULCC and PAs data to explore these interactions within the terrestrial ecosystem model (TEM). We found that intensive LULCC occurred in the conterminous United States from 1700 to 2005. More than 3 million km2 of forest, grassland and shrublands were converted into agricultural lands, which caused 10,607Tg C release from land ecosystems to atmosphere. PAs had experienced little LULCC as they were generally established in the 20th century after most of the agricultural expansion had occurred. PAs initially acted as a carbon source due to land use legacies, but their accumulated carbon budget switched to a carbon sink in the 1960s, sequestering an estimated 1,642Tg C over 1700-2005, or 13.4% of carbon losses in non-PAs. We also find that PAs maintain larger carbon stocks and continue sequestering carbon in recent years (2001-2005), but at a lower rate due to increased heterotrophic respiration as well as lower productivity associated to aging ecosystems. It is essential to continue efforts to maintain resilient, biodiverse ecosystems and avoid large-scale disturbances that would release large amounts of carbon in PAs.

Land Cover Changes (1963–2010) and Their Environmental Factors in the Upper Danube Floodplain

To analyze the changes in the Upper Danube Floodplain, we used aerial photos to quantify the change of landscape pattern from 1963 to 2010. We focused on typical floodplain habitats, i.e., riparian forest and floodplain grassland. We used landscape metrics and transformation matrix to explore changes in land cover structure and composition. The active floodplain experienced increasing fragmentation from 1963 to 2010. Despite an increase of aggregation, riparian forest suffered a 2.3% area loss from 1995 to 2010. Arable land in the active floodplain declined by 28.5%, while its patch size significantly increased. Elevation, distance to river and soil quality were the most relevant environmental factors for the land cover change in the floodplain. Higher soil quality or longer distance to river led to an increase of conversion from grassland into arable land; grassland patches with poorer soil quality were likely to change into riparian forest; riparian forest closer to the river and with a lower height above mean water level tended to remain stable. This comprehensive understanding of historical land cover change and environmental factors is needed for the enhancement of landscape functions and sustainable development in the floodplain.

Diversification and democracy

Does diversification of an economy improve the chances of democracy? In theory, diversification may reduce elite cohesion and improve citizens’ outside options, making democracy more likely. This paper estimates the effect of export diversification on democracy, using data from 143 countries. We use variability within countries in fertile soil as an instrument for diversification, controlling for country size. To address the possibility that current fertile soil variability may have been influenced by historical country characteristics that could also have affected democracy today, we control for historical changes in land cover. We identify a statistically significant, positive effect of diversification on democracy.

Sensitivity of land use change emission estimates to historical land use and land cover mapping

AbstractThe carbon emissions from land use and land cover change (ELUC) are an important anthropogenic component of the global carbon budget. Yet these emissions have a large uncertainty. Uncertainty in historical land use and land cover change (LULCC) maps and their implementation in global vegetation models is one of the key sources of the spread of ELUC calculated by global vegetation models. In this study, we used the Organizing Carbon and Hydrology in Dynamic Ecosystems terrestrial biosphere model to investigate how the different transition rules to define the priority of conversion from natural vegetation to agricultural land affect the historical reconstruction of plant functional types (PFTs) and ELUC. First, we reconstructed 10 sets of historical PFT maps using different transition rules and two methods. Then, we calculated ELUC from these 10 different historical PFT maps and an additional published PFT reconstruction, using the difference between two sets of simulations (with and without LULCC). The total area of forest loss is highly correlated with the total simulated ELUC (R2 = 0.83, P < 0.001) across the reconstructed PFT maps, which indicates that the choice of transition rules is a critical (and often overlooked) decision affecting the simulated ELUC. In addition to the choice of a transition rule, the initial land cover map and the reconstruction method for the reconstruction of historical PFT maps have an important impact on the resultant estimates of ELUC.

Impacts of Land-Use/Land-Cover Change on Afternoon Precipitation over North America

Abstract This study investigates the impacts of historical land-cover change on summer afternoon precipitation over North America using the Community Earth System Model. Using land–atmosphere coupling metrics, this study examines the sensitivity of afternoon atmospheric conditions to morning land surface states and fluxes that are altered by land-cover changes before and since 1850. The deforestation in the eastern United States prior to 1850 leads to increased latent but decreased sensible heat flux during the morning and a reduction in afternoon precipitation over the southern regions of the U.S. East Coast. The agricultural expansion over the Great Plains since preindustrial times shows similar effects on surface fluxes but results in a significant widespread increase in precipitation over the crop area. The coupling metrics exhibit a strong positive soil moisture–precipitation relationship over the Great Plains. Impacts of land-cover change on precipitation manifest through changes in rainfall frequency, rather than intensity, that are largely controlled by the distribution of CAPE as the trigger of convective precipitation. However, deforestation and later reforestation over the eastern United States, where coupling properties are different than the Great Plains, do not have as dominant an effect on afternoon precipitation. Additionally, precipitation over parts of the U.S. Southwest decreases in this model during the earlier period of East Coast deforestation, owing to changes in the large-scale circulation over North America driven by land-use changes prior to 1850.

Historical Land-Cover Change Impacts on Climate: Comparative Assessment of LUCID and CMIP5 Multimodel Experiments

Abstract During the industrial period, many regions experienced a reduction in forest cover and an expansion of agricultural areas, in particular North America, northern Eurasia, and South Asia. Here, results from the Land-Use and Climate, Identification of Robust Impacts (LUCID) and CMIP5 model intercomparison projects are compared in order to investigate how land-cover changes (LCC) in these regions have locally impacted the biophysical land surface properties, like albedo and evapotranspiration, and how this has affected seasonal mean temperature as well as its diurnal cycle. The impact of LCC is extracted from climate simulations, including all historical forcings, using a method that is shown to capture well the sign and the seasonal cycle of the impacts diagnosed from single-forcing experiments in most cases. The model comparison reveals that both the LUCID and CMIP5 models agree on the albedo-induced reduction of mean winter temperatures over midlatitudes. In contrast, there is less agreement concerning the response of the latent heat flux and, subsequently, mean temperature during summer, when evaporative cooling plays a more important role. Overall, a majority of models exhibit a local warming effect of LCC during this season, contrasting with results from the LUCID studies. A striking result is that none of the analyzed models reproduce well the changes in the diurnal cycle identified in present-day observations of the effect of deforestation. However, overall the CMIP5 models better simulate the observed summer daytime warming effect compared to the LUCID models, as well as the winter nighttime cooling effect.

Paying the colonization credit: converging plant species richness in ancient and post-agricultural forests in NE Germany over five decades

Massive historical land cover changes in the Central European lowlands have resulted in a forest distribution that now comprises small remnants of ancient forests and more recently established post-agricultural forests. Here, land-use history is considered a key driver of recent herb-layer community changes, where an extinction debt in ancient forest remnants and/or a colonization credit in post-agricultural forests are being paid over time. On a regional scale, these payments should in theory lead toward a convergence in species richness between ancient and post-agricultural forests over time. In this study, we tested this assumption with a resurvey of 117 semi-permanent plots in the well-studied deciduous forests of the Prignitz region (Brandenburg, NE Germany), where we knew that the plant communities of post-agricultural stands exhibit a colonization credit while the extinction debt in ancient stands has largely been paid. We compared changes in the species richness of all herb layer species, forest specialists and ancient forest indicator species between ancient and post-agricultural stands with linear mixed effect models and determined the influence of patch connectivity on the magnitude of species richness changes. Species richness increased overall, but the richness of forest specialists increased significantly more in post-agricultural stands and was positively influenced by higher patch connectivity, indicating a convergence in species richness between the ancient and post-agricultural stands. Furthermore, the richness of ancient forest indicator species only increased significantly in post-agricultural stands. For the first time, we were able to verify a gradual payment of the colonization credit in post-agricultural forest stands using a comparison of actual changes in temporal species richness.

Fragmentation metric proxies provide insights into historical biodiversity loss in critically endangered grassland

Landscape transformation causes habitat loss and fragmentation, which poses the greatest threat to biodiversity globally. In a fragmented landscape the persistence of species is affected by the amount of habitat and the spatial attributes of individual habitat patches. As baseline biodiversity information is often unavailable to assess the effects of transformation on biodiversity, quantifying changes in patch metrics over time could be a useful indicator of biodiversity changes in fragmented landscapes. We investigate historical land cover changes due to increased anthropogenic land uses in a highly fragmented, critically endangered grassland, the Woodbush Granite Grassland, South Africa. We test how the spatial attributes of habitat patches were affected by habitat loss and fragmentation over two extended time-periods, and use these results to infer likely threats to biodiversity over these periods. We used repeat aerial photography to analyse the drivers and extent of land cover loss and the changes in five fragmentation metrics over a 60year period. The overall grassland extent decreased significantly over the 60-year period, mainly due to increased timber plantations, with an estimated 6.1% of the original extent of the grassland remaining in 2008. Increases in patch isolation due to habitat loss were most pronounced between 1948 and 1977, while between 1977 and 2008 patch sizes decreased and edge effects increased. This extensive habitat loss and increase in fragmentation are likely to have had considerable impacts on the biodiversity of the region, which is supported by anecdotal evidence of species extinctions and local extinctions. Because so little of the vegetation type remains, it is imperative that the last vestiges of this vegetation type are protected from transformation and further habitat degradation. In summary, we show how, faced with a lack of biodiversity data, fragmentation patch metrics can be used to quantify threats to biodiversity.

Agricultural cropland mapping using black-and-white aerial photography, Object-Based Image Analysis and Random Forests

Land-use and land-cover (LULC) conversions have an important impact on land degradation, erosion and water availability. Information on historical land cover (change) is crucial for studying and modelling land- and ecosystem degradation. During the past decades major LULC conversions occurred in Africa, Southeast Asia and South America as a consequence of a growing population and economy. Most distinct is the conversion of natural vegetation into cropland. Historical LULC information can be derived from satellite imagery, but these only date back until approximately 1972. Before the emergence of satellite imagery, landscapes were monitored by black-and-white (B&W) aerial photography. This photography is often visually interpreted, which is a very time-consuming approach. This study presents an innovative, semi-automated method to map cropland acreage from B&W photography. Cropland acreage was mapped on two study sites in Ethiopia and in The Netherlands. For this purpose we used Geographic Object-Based Image Analysis (GEOBIA) and a Random Forest classification on a set of variables comprising texture, shape, slope, neighbour and spectral information. Overall mapping accuracies attained are 90% and 96% for the two study areas respectively. This mapping method increases the timeline at which historical cropland expansion can be mapped purely from brightness information in B&W photography up to the 1930s, which is beneficial for regions where historical land-use statistics are mostly absent.

Forestland-cover changes in China’s tropical area: Historical patterns, implications, and policy options—a case study from Xishuangbanna

ABSTRACTTo effectively conserve tropical forested areas, it is useful to study and understand historical land-cover changes and local people’s attitudes toward the current land-uses. Using forest inventory data, and data collected from a survey of 145 households, we explored the forestland-cover changes, within the past 50 yr, in Xishuangbanna, China, and assessed the local residents’ perceptions toward the existing forestland management schemes. Our analysis showed that although forestland coverage has increased during the time-period studied, the increase can be mostly attributed to the expansion of rubber plantations. Forest degradation continues to be an issue in the area studied. The government’s attempts to mitigate the effects of rubber monocultures, by promoting environment-friendly plantations, have been proven challenging, which was mainly due to locals’ unfavorable view of the plan. Also, because of the recent decreasing prices of dry rubber, many locals have lost their interest in managing the forest plots they own, hindering further the successful implementation of the plan. Considering these challenges, and the strong negative effects of rubber monocultures on biodiversity, we argue that the current incentives should be further strengthened to promote more efficiently the government’s “Environment-Friendly Ecological Rubber Plantations” plan, and the joint management of the locals’ forest plots.

Impacts of historical climate and land cover changes on fine particulate matter (PM<sub>2.5</sub>) air quality in East Asia between 1980 and 2010

Abstract. To examine the effects of changes in climate, land cover and land use (LCLU), and anthropogenic emissions on fine particulate matter (PM2.5) between the 5-year periods 1981–1985 and 2007–2011 in East Asia, we perform a series of simulations using a global chemical transport model (GEOS-Chem) driven by assimilated meteorological data and a suite of land cover and land use data. Our results indicate that climate change alone could lead to a decrease in wintertime PM2.5 concentration by 4.0–12.0 µg m−3 in northern China, but to an increase in summertime PM2.5 by 6.0–8.0 µg m−3 in those regions. These changes are attributable to the changing chemistry and transport of all PM2.5 components driven by long-term trends in temperature, wind speed and mixing depth. The concentration of secondary organic aerosol (SOA) is simulated to increase by 0.2–0.8 µg m−3 in both summer and winter in most regions of East Asia due to climate change alone, mostly reflecting higher biogenic volatile organic compound (VOC) emissions under warming. The impacts of LCLU change alone on PM2.5 (−2.1 to +1.3 µg m−3) are smaller than that of climate change, but among the various components the sensitivity of SOA and thus organic carbon to LCLU change (−0.4 to +1.2 µg m−3) is quite significant especially in summer, which is driven mostly by changes in biogenic VOC emissions following cropland expansion and changing vegetation density. The combined impacts show that while the effect of climate change on PM2.5 air quality is more pronounced, LCLU change could offset part of the climate effect in some regions but exacerbate it in others. As a result of both climate and LCLU changes combined, PM2.5 levels are estimated to change by −12.0 to +12.0 µg m−3 across East Asia between the two periods. Changes in anthropogenic emissions remain the largest contributor to deteriorating PM2.5 air quality in East Asia during the study period, but climate and LCLU changes could lead to a substantial modification of PM2.5 levels.

Is extensive terrestrial carbon dioxide removal a ‘green’ form of geoengineering? A global modelling study

Biological carbon sequestration through implementation of biomass plantations is currently being discussed as an option for climate engineering (CE) should mitigation efforts fail to substantially reduce greenhouse gas emissions. As it is a plant-based CE option that extracts CO2 from the atmosphere, it might be considered a ‘green’ CE method that moves the biosphere closer to its natural, i.e. pre-Neolithic, state. Here, we test this hypothesis by comparing the biogeochemical (water- and carbon-related) changes induced by biomass plantations compared to those induced by historical human land cover and land use change. Results indicate that large-scale biomass plantations would produce a biogeochemical shift in the terrestrial biosphere which is, in absolute terms, even larger than that already produced by historical land use change. However, the nature of change would differ between a world dominated by biomass plantations and the current world inheriting the effects of historical land use, highlighting that large-scale tCDR would represent an additional distinct and massive human intervention into the biosphere. Contrasting the limited possibilities of tCDR to reduce the pressure on the planetary boundary for climate change with the potential negative implications on the status of other planetary boundaries highlights that tCDR via biomass plantations should not be considered a ‘green’ CE method but a full scale engineering intervention.