Uncertainties in the land-use flux resulting from land-use change reconstructions and gross land transitions

Land-use and land-cover (LUC) changes are a key uncertainty when attributing changes in measured atmospheric CO2 concentration to its sinks and sources and must also be much better understood to determine the possibilities for land-based climate change mitigation, especially in the light of human demand on other land-based resources. On the spatial scale typically used in terrestrial ecosystem models (0.5 or 1°) changes in LUC over time periods of a few years or more can include bidirectional changes on the sub-grid level, such as the parallel expansion and abandonment of agricultural land (e.g. in shifting cultivation) or cropland–grassland conversion (and vice versa). These complex changes between classes within a grid cell have often been neglected in previous studies, and only net changes of land between natural vegetation cover, cropland and pastures accounted for, mainly because of a lack of reliable high-resolution historical information on gross land transitions, in combination with technical limitations within the models themselves. In the present study we applied a state-of-the-art dynamic global vegetation model with a detailed representation of croplands and carbon–nitrogen dynamics to quantify the uncertainty in terrestrial ecosystem carbon stocks and fluxes arising from the choice between net and gross representations of LUC. We used three frequently applied global, one recent global and one recent European LUC datasets, two of which resolve gross land transitions, either in Europe or in certain tropical regions. When considering only net changes, land-use-transition uncertainties (expressed as 1 standard deviation around decadal means of four models) in global carbon emissions from LUC (ELUC) are ±0.19, ±0.66 and ±0.47 Pg C a−1 in the 1980s, 1990s and 2000s, respectively, or between 14 and 39 % of mean ELUC. Carbon stocks at the end of the 20th century vary by ±11 Pg C for vegetation and ±37 Pg C for soil C due to the choice of LUC reconstruction, i.e. around 3 % of the respective C pools. Accounting for sub-grid (gross) land conversions significantly increased the effect of LUC on global and European carbon stocks and fluxes, most noticeably enhancing global cumulative ELUC by 33 Pg C (1750–2014) and entailing a significant reduction in carbon stored in vegetation, although the effect on soil C stocks was limited. Simulations demonstrated that assessments of historical carbon stocks and fluxes are highly uncertain due to the choice of LUC reconstruction and that the consideration of different contrasting LUC reconstructions is needed to account for this uncertainty. The analysis of gross, in addition to net, land-use changes showed that the full complexity of gross land-use changes is required in order to accurately predict the magnitude of LUC change emissions. This introduces technical challenges to process-based models and relies on extensive information regarding historical land-use transitions

Climate and parameter sensitivity and induced uncertainties in carbon stock projections for European forests (using LPJ-GUESS 4.0)

Understanding uncertainties and sensitivities of projected ecosystem dynamics under environmental change is of immense value for research and climate change policy. Here, we analyze sensitivities (change in model outputs per unit change in inputs) and uncertainties (changes in model outputs scaled to uncertainty in inputs) of vegetation dynamics under climate change, projected by a state-of-the-art dynamic vegetation model (LPJ-GUESS v4.0) across European forests (the species Picea abies, Fagus sylvatica and Pinus sylvestris), considering uncertainties of both model parameters and environmental drivers. We find that projected forest carbon fluxes are most sensitive to photosynthesis-, water-, and mortality-related parameters, while predictive uncertainties are dominantly induced by environmental drivers and parameters related to water and mortality. The importance of environmental drivers for predictive uncertainty increases with increasing temperature. Moreover, most of the interactions of model inputs (environmental drivers and parameters) are between environmental drivers themselves or between parameters and environmental drivers. In conclusion, our study highlights the importance of environmental drivers not only as contributors to predictive uncertainty in their own right but also as modifiers of sensitivities and thus uncertainties in other ecosystem processes. Reducing uncertainty in mortality-related processes and accounting for environmental influence on processes should therefore be a focus in further model development

The effect of forest owner decision-making, climatic change and societal demands on land-use change and ecosystem service provision in Sweden

The uncertain effects of climatic change and changing demands for ecosystem services on the distribution of forests and their levels of service provision require assessments of future land-use change, ecosystem service provision, and how ecosystem service demands may be met. We present CRAFTY-Sweden, an agent-based, land-use model that incorporates land owner behaviour and decision-making in modelling future ecosystem service provision in the Swedish forestry sector. Future changes were simulated under scenarios of socio-economic and climatic change between 2010 and 2100. The simulations indicate that the influence of climatic change (on land productivities) may be less important than that of socio-economic change or behavioural differences. Simulations further demonstrate that the variability in land owner and societal behaviour has a substantial role in determining the direction and impact of land-use change. The results indicate a sizeable increase in timber harvesting in coming decades, which together with a substantial decoupling between supply and demand for forest ecosystem services highlights the challenge of continuously meeting demands for ecosystem services over long periods of time. There is a clear need for model applications of this kind to better understand the variation in ecosystem service provision in the forestry sector, and other associated land-use changes

Trade-Offs for Climate-Smart Forestry in Europe Under Uncertain Future Climate

Forests mitigate climate change by storing carbon and reducing emissions via substitution effects of wood products. Additionally, they provide many other important ecosystem services (ESs), but are vulnerable to climate change; therefore, adaptation is necessary. Climate-smart forestry combines mitigation with adaptation, whilst facilitating the provision of many ESs. This is particularly challenging due to large uncertainties about future climate. Here, we combined ecosystem modeling with robust multi-criteria optimization to assess how the provision of various ESs (climate change mitigation, timber provision, local cooling, water availability, and biodiversity habitat) can be guaranteed under a broad range of climate futures across Europe. Our optimized portfolios contain 29% unmanaged forests, and implicate a successive conversion of 34% of coniferous to broad-leaved forests (11% vice versa). Coppices practically vanish from Southern Europe, mainly due to their high water requirement. We find the high shares of unmanaged forests necessary to keep European forests a carbon sink while broad-leaved and unmanaged forests contribute to local cooling through biogeophysical effects. Unmanaged forests also pose the largest benefit for biodiversity habitat. However, the increased shares of unmanaged and broad-leaved forests lead to reductions in harvests. This raises the question of how to meet increasing wood demands without transferring ecological impacts elsewhere or enhancing the dependence on more carbon-intensive industries. Furthermore, the mitigation potential of forests depends on assumptions about the decarbonization of other industries and is consequently crucially dependent on the emission scenario. Our findings highlight that trade-offs must be assessed when developing concrete strategies for climate-smart forestry

State-of-the-art capabilities in LPJ-GUESS

LPJ-GUESS is an advanced DGVM including detailed forest demography and management, croplands, wetlands, specialised arctic processes, emissions of nonCO2 GHGs and a highly flexible land-use change scheme which tracks transitions between different land-uses. It is the vegetation component of the EC-Earth CMIP6 ESM, the RCA-GUESS regional ESM, and also has a European mode operating at tree species level

Climate and parameter sensitivity and induced uncertainties in carbon stock projections for European forests (using LPJ-GUESS 4.0)

Understanding uncertainties and sensitivities of projected ecosystem dynamics under environmental change is of immense value for research and climate change policy. Here, we analyze sensitivities (change in model outputs per unit change in inputs) and uncertainties (changes in model outputs scaled to uncertainty in inputs) of vegetation dynamics under climate change, projected by a state-of-the-art dynamic vegetation model (LPJ-GUESS v4.0) across European forests (the species Picea abies, Fagus sylvatica and Pinus sylvestris), considering uncertainties of both model parameters and environmental drivers. We find that projected forest carbon fluxes are most sensitive to photosynthesis-, water-, and mortality-related parameters, while predictive uncertainties are dominantly induced by environmental drivers and parameters related to water and mortality. The importance of environmental drivers for predictive uncertainty increases with increasing temperature. Moreover, most of the interactions of model inputs (environmental drivers and parameters) are between environmental drivers themselves or between parameters and environmental drivers. In conclusion, our study highlights the importance of environmental drivers not only as contributors to predictive uncertainty in their own right but also as modifiers of sensitivities and thus uncertainties in other ecosystem processes. Reducing uncertainty in mortality-related processes and accounting for environmental influence on processes should therefore be a focus in further model development

A continental-scale validation of ecosystem service models

Faced with environmental degradation, governments worldwide are developing policies to safeguard ecosystem services (ES). Many ES models exist to support these policies, but they are generally poorly validated, especially at large scales, which undermines their credibility. To address this gap, we describe a study of multiple models of five ES, which we validate at an unprecedented scale against 1675 data points across sub-Saharan Africa. We find that potential ES (biophysical supply of carbon and water) are reasonably well predicted by the existing models. These potential ES models can also be used as inputs to new models for realised ES (use of charcoal, firewood, grazing resources and water), by adding information on human population density. We find that increasing model complexity can improve estimates of both potential and realised ES, suggesting that developing more detailed models of ES will be beneficial. Furthermore, in 85% of cases, human population density alone was as good or a better predictor of realised ES than ES models, suggesting that it is demand, rather than supply that is predominantly determining current patterns of ES use. Our study demonstrates the feasibility of ES model validation, even in data-deficient locations such as sub-Saharan Africa. Our work also shows the clear need for more work on the demand side of ES models, and the importance of model validation in providing a stronger base to support policies which seek to achieve sustainable development in support of human well-being

Transcription, splicing and genetic structure within the human endogenous retroviral HERV-H family.

Human endogenous retroviruses (HERVs) are remains of ancient retroviral infections of the germ line and constitute as much as 3 % of the human genome. HERVs are genetic elements that potentially may provide important biological functions by several different mechanisms. The ability to transpose long after the initial insertion into the germ line may provide a potent source of insertional mutagenesis, influencing adjacent cellular genes by the promoter and enhancer functions of the retroviral long terminal repeats (LTRs). Expression of retroviral proteins in human cells may provide important functions both for a resistance to infections by exogenous retroviruses and for normal cell function in the placenta and immune cells. Many of these postulated actions would act through the envelope (Env) glycoproteins, which possess fusogenic and immunosuppressive properties. In the present investigation, various aspects of one of the largest HERV families, HERV-H, was studied. First, HERV-H transcripts potentially encoding immunosuppressive Env proteins were detected in various cell types, e. g. leukocytes and brain tissue. Then the splicing pattern of HERV-H transcripts coding for Env proteins were studied, disclosing complex alternative splicing. Hybrid spliced transcripts containing sequences from HERV-H and another family, HERV-E, were also characterized in these studies. Lastly, the first example of a coding-competent HERV-H element was isolated, possessing a complete open reading frame for the Env protein. The combined results may provide an important basis for studying the presence of immunosuppressive Env protein-encoding HERV-H elements and the expression and function of these proteins

Full-length HERV-H elements with env SU open reading frames in the human genome

Human endogenous retroviruses (HERVs) are estimated to represent at least 1% of the human genome. An HERV-H env SU sequence (HERV-H19) was used to screen the high-throughput (htgs) and nonredundant (nr) databases for other HERV-H SU open reading frames (ORFs) and thus possible functional proteins. Using PCR with primers derived from HERV-H19 SU, we also obtained several new sequences with ORFs from a human DNA sample. In a phylogenetic analysis, ORF-containing sequences clustered with HERV-H sequences from chromosomes 1 and 2. SU ORF- and non-SU ORF-containing elements had about the same difference between 5' and 3' long terminal repeats (LTRs) (about 4%), indicating a similar time of integration. SU ORF sequences had a moderately high number of synonymous-versus-nonsynonymous mutations, which indicates a selection for maintenance of the HERV-H SU ORFs

Coamplification and Dispersion of Adjacent Human Endogenous Retroviral HERV-H and HERV-E Elements; Presence of Spliced Hybrid Transcripts in Normal Leukocytes

AbstractIn an RT–PCR study of HERV-H spliced subgenomic transcripts, we found transcripts with HERV-H leader and protease-encoding sequences spliced to HERV-E integrase-encoding sequences in lymphocytes from healthy blood donors. In other cell types, including two T-cell leukemia cell lines, these transcripts were absent. The PCR fragments of the hybrid transcripts contained two open reading frames (ORFs). One was a hybrid HERV-H protease/HERV-E integrase ORF and the other was the HERV-E envelope surface glycoprotein ORF. Alternative splice products were also identified. The genomic DNA origin of the hybrid transcripts was shown to be a HERV-H element with a large 3′-end deletion, adjacent to a HERV-E element lacking the 5′-LTR. This hybrid structure was shown to be amplified and dispersed to six different human chromosomes. Thus, a relatively large part of full-length HERV-E elements (15–20%) is potentially under the transcriptional control of HERV-H LTRs. The HERV-H/HERV-E junction was present in multiple copies also in the chimpanzee and gorilla, but not in the orangutan or old world monkeys