scholarly journals Smaller global and regional carbon emissions from gross land use change when considering sub-grid secondary land cohorts in a global dynamic vegetation model

2017 ◽  
Author(s):  
Chao Yue ◽  
Philippe Ciais ◽  
Wei Li
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Carbon Emissions ◽  
Shifting Cultivation ◽  
Secondary Forests ◽  
Forest Age ◽  
Priority Rules ◽  
Forest Clearing ◽  
Historical Land Use ◽  
Wood Harvest

Abstract. Several modeling studies reported elevated carbon emissions from historical land use change (LUC) by including bi-directional transitions at the sub-grid scale (termed gross land use change). This has implication on the estimation of so-called residual land CO2 sink over undisturbed lands. However, in most dynamic global vegetation models (DGVM), forests and/or other land use types are represented with a single sub-grid tile, without accounting for secondary lands that are often involved in shifting cultivation or wood harvest. As a result, land use change emissions (ELUC) are likely overestimated, because it is high-biomass mature forests instead of low-biomass secondary forests that are cleared. Here we investigated the effects of including sub-grid forest age dynamics in a DGVM on historical ELUC over 1501–2005. We run two simulations, one with no forest age (Sageless) and the other with sub-grid secondary forests of different age classes whose demography is driven by historical land use change (Sage). Estimated global ELUC for 1501–2005 are 179 Pg C in Sage compared to 199 Pg C in Sageless. The lower emissions in Sage arise mainly from shifting cultivation in the tropics, being of 27 Pg C in Sage against 46 Pg C in Sageless. Estimated cumulative ELUC from wood harvest in the Sage simulation (31 Pg C) are however slightly higher than Sageless (27 Pg C), because secondary forests simulated in Sage are insufficient to meet the prescribed harvest area, leading to the harvest of old forests. This result depends on pre-defined forest clearing priority rules given a simulated portfolio of differently aged forests in the model. Our results highlight that although gross land use change as a former missing emission component is included by a growing number of DGVMs, its contribution to overall ELUC tends to be overestimated, unless low-biomass secondary forests are properly represented.

scholarly journals Smaller global and regional carbon emissions from gross land use change when considering sub-grid secondary land cohorts in a global dynamic vegetation model

2018 ◽  
Vol 15 (4) ◽  
pp. 1185-1201 ◽  
Author(s):  
Chao Yue ◽  
Philippe Ciais ◽  
Wei Li
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Carbon Emissions ◽  
Shifting Cultivation ◽  
Secondary Forest ◽  
Secondary Forests ◽  
Forest Age ◽  
Rotation Length ◽  
Historical Land Use ◽  
Wood Harvest

Abstract. Several modelling studies reported elevated carbon emissions from historical land use change (ELUC) by including bidirectional transitions on the sub-grid scale (termed gross land use change), dominated by shifting cultivation and other land turnover processes. However, most dynamic global vegetation models (DGVMs) that have implemented gross land use change either do not account for sub-grid secondary lands, or often have only one single secondary land tile over a model grid cell and thus cannot account for various rotation lengths in shifting cultivation and associated secondary forest age dynamics. Therefore, it remains uncertain how realistic the past ELUC estimations are and how estimated ELUC will differ between the two modelling approaches with and without multiple sub-grid secondary land cohorts – in particular secondary forest cohorts. Here we investigated historical ELUC over 1501–2005 by including sub-grid forest age dynamics in a DGVM. We run two simulations, one with no secondary forests (Sageless) and the other with sub-grid secondary forests of six age classes whose demography is driven by historical land use change (Sage). Estimated global ELUC for 1501–2005 is 176 Pg C in Sage compared to 197 Pg C in Sageless. The lower ELUC values in Sage arise mainly from shifting cultivation in the tropics under an assumed constant rotation length of 15 years, being 27 Pg C in Sage in contrast to 46 Pg C in Sageless. Estimated cumulative ELUC values from wood harvest in the Sage simulation (31 Pg C) are however slightly higher than Sageless (27 Pg C) when the model is forced by reconstructed harvested areas because secondary forests targeted in Sage for harvest priority are insufficient to meet the prescribed harvest area, leading to wood harvest being dominated by old primary forests. An alternative approach to quantify wood harvest ELUC, i.e. always harvesting the close-to-mature forests in both Sageless and Sage, yields similar values of 33 Pg C by both simulations. The lower ELUC from shifting cultivation in Sage simulations depends on the predefined forest clearing priority rules in the model and the assumed rotation length. A set of sensitivity model runs over Africa reveal that a longer rotation length over the historical period likely results in higher emissions. Our results highlight that although gross land use change as a former missing emission component is included by a growing number of DGVMs, its contribution to overall ELUC remains uncertain and tends to be overestimated when models ignore sub-grid secondary forests.

scholarly journals Representing anthropogenic gross land use change, wood harvest and forest age dynamics in a global vegetation model ORCHIDEE-MICT (r4259)

2017 ◽  
Author(s):  
Chao Yue ◽  
Philippe Ciais ◽  
Sebastiaan Luyssaert ◽  
Wei Li ◽  
Matthew J. McGrath ◽  
...  
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Shifting Cultivation ◽  
Agricultural Land ◽  
Traditional Approach ◽  
Grid Cell ◽  
Secondary Forests ◽  
Vegetation Model ◽  
Data Set ◽  
Wood Harvest

Abstract. Land use change (LUC) is a fundamental anthropogenic disturbance in the global carbon cycle. Here we present model developments in a global dynamic vegetation model ORCHIDEE-MICT for more realistic representation of LUC processes. First, we included gross land use change (primarily shifting cultivation) and forest wood harvest in addition to net land use change. Second, we included sub-grid even-aged land cohorts to represent secondary forests, and to keep track of the age of agricultural lands since LUC, which are associated with variable soil carbon stocks. Combination of these two features allows simulating shifting cultivation with a short rotation length involving mainly secondary forests instead of primary ones. This is in contrast with the traditional approach where a single patch is used for a given land cover type in a model grid cell and forests are thus close to primary ones. We have tested the model over Southern Africa for the period 1501–2005 forced by a historical land use change data set. Including gross land use change and wood harvest has increased LUC emissions in both simulations with (Sage) and without (Sageless) sub-grid secondary forests, but larger increase is found in Sageless (by a factor of 2) than Sage (by a factor of 1.5). Emissions from bi-directional land turnover alone are 35 % lower in Sage than Sageless, mainly because the secondary forests cleared for agricultural land have a lower aboveground biomass than primary ones. We argue that, without representing sub-grid land cohort demography, the additional emissions from land turnover/gross land use change are overestimated. In addition, our developments provide possibilities to account for continental or global forest demographic change resulting from past anthropogenic and natural disturbances.

scholarly journals Representing anthropogenic gross land use change, wood harvest, and forest age dynamics in a global vegetation model ORCHIDEE-MICT v8.4.2

2018 ◽  
Vol 11 (1) ◽  
pp. 409-428 ◽  
Author(s):  
Chao Yue ◽  
Philippe Ciais ◽  
Sebastiaan Luyssaert ◽  
Wei Li ◽  
Matthew J. McGrath ◽  
...  
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Southern Africa ◽  
Shifting Cultivation ◽  
Forest Recovery ◽  
Secondary Forests ◽  
Miombo Woodlands ◽  
Agricultural Abandonment ◽  
Vegetation Model ◽  
Wood Harvest

Abstract. Land use change (LUC) is among the main anthropogenic disturbances in the global carbon cycle. Here we present the model developments in a global dynamic vegetation model ORCHIDEE-MICT v8.4.2 for a more realistic representation of LUC processes. First, we included gross land use change (primarily shifting cultivation) and forest wood harvest in addition to net land use change. Second, we included sub-grid evenly aged land cohorts to represent secondary forests and to keep track of the transient stage of agricultural lands since LUC. Combination of these two features allows the simulation of shifting cultivation with a rotation length involving mainly secondary forests instead of primary ones. Furthermore, a set of decision rules regarding the land cohorts to be targeted in different LUC processes have been implemented. Idealized site-scale simulation has been performed for miombo woodlands in southern Africa assuming an annual land turnover rate of 5 % grid cell area between forest and cropland. The result shows that the model can correctly represent forest recovery and cohort aging arising from agricultural abandonment. Such a land turnover process, even though without a net change in land cover, yields carbon emissions largely due to the imbalance between the fast release from forest clearing and the slow uptake from agricultural abandonment. The simulation with sub-grid land cohorts gives lower emissions than without, mainly because the cleared secondary forests have a lower biomass carbon stock than the mature forests that are otherwise cleared when sub-grid land cohorts are not considered. Over the region of southern Africa, the model is able to account for changes in different forest cohort areas along with the historical changes in different LUC activities, including regrowth of old forests when LUC area decreases. Our developments provide possibilities to account for continental or global forest demographic change resulting from past anthropogenic and natural disturbances.

scholarly journals Contextualizing Landscape-Scale Forest Cover Loss in the Democratic Republic of Congo (DRC) between 2000 and 2015

Land ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 23 ◽  
Author(s):  
Giuseppe Molinario ◽  
Matthew Hansen ◽  
Peter Potapov ◽  
Alexandra Tyukavina ◽  
Stephen Stehman
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Shifting Cultivation ◽  
Democratic Republic ◽  
Democratic Republic Of Congo ◽  
Forest Loss ◽  
Republic Of Congo ◽  
Forest Clearing ◽  
New Forest ◽  
The Impact

Shifting cultivation has been shown to be the primary cause of land use change in the Democratic Republic of Congo (DRC). Traditionally, forested and fallow land are rotated in a slash and burn cycle that has created an agricultural mosaic, including secondary forest, known as the rural complex. This study investigates the land use context of new forest clearing (during 2000–2015) in primary forest areas outside of the established rural complex. These new forest clearings occur as either rural complex expansion (RCE) or isolated forest perforations (IFP), with consequent implications on the forest ecosystem and biodiversity habitat. During 2000–2015, subsistence agriculture was the dominant driver of forest clearing for both extension of settled areas and pioneer clearings removed from settled areas. Less than 1% of clearing was directly attributable to land uses such as mining, plantations, and logging, showing that the impact of commercial operations in the DRC is currently dwarfed by a reliance on small-holder shifting cultivation. However, analyzing the landscape context showed that large-scale agroindustry and resource extraction activities lead to increased forest loss and degradation beyond their previously-understood footprints. The worker populations drawn to these areas create communities that rely on shifting cultivation and non-timber forest products (NTFP) for food, energy, and building materials. An estimated 12% of forest loss within the RCE and 9% of the area of IFP was found to be within 5 km of mines, logging, or plantations. Given increasing demographic and commercial pressures on DRC’s forests, it will be crucial to factor in this landscape-level land use change dynamic in land use planning and sustainability-focused governance.

scholarly journals Past and future carbon fluxes from land use change, shifting cultivation and wood harvest

Tellus B ◽  
2014 ◽  
Vol 66 (1) ◽  
pp. 23188 ◽  
Author(s):  
Benjamin D. Stocker ◽  
Fabian Feissli ◽  
Kuno M. Strassmann ◽  
Renato Spahni ◽  
Fortunat Joos
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Shifting Cultivation ◽  
Carbon Fluxes ◽  
Wood Harvest

Historical land use change and associated carbon emissions in Brazil from 1940 to 1995

2012 ◽  
Vol 26 (2) ◽  
pp. n/a-n/a ◽  
Author(s):  
Christiane Cavalcante Leite ◽  
Marcos Heil Costa ◽  
Britaldo Silveira Soares-Filho ◽  
Letícia de Barros Viana Hissa
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Carbon Emissions ◽  
Historical Land Use

Carbon emissions from land-use change: an analysis of causal factors in Chiapas, Mexico

2006 ◽  
Vol 12 (6) ◽  
pp. 1213-1235 ◽  
Author(s):  
M. A. Castillo-Santiago ◽  
A. Hellier ◽  
R. Tipper ◽  
B. H. J. de Jong
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Carbon Emissions ◽  
Causal Factors

scholarly journals A Bayesian ensemble data assimilation to constrain model parameters and land-use carbon emissions

2018 ◽  
Vol 15 (9) ◽  
pp. 2909-2930 ◽  
Author(s):  
Sebastian Lienert ◽  
Fortunat Joos
Keyword(s):  
Land Use ◽  
Carbon Emissions ◽  
Latin Hypercube Sampling ◽  
Historical Period ◽  
Model Parameters ◽  
Dynamic Global Vegetation Model ◽  
Order Of Magnitude ◽  
The Difference ◽  
Wood Harvest ◽  
Global Vegetation

Abstract. A dynamic global vegetation model (DGVM) is applied in a probabilistic framework and benchmarking system to constrain uncertain model parameters by observations and to quantify carbon emissions from land-use and land-cover change (LULCC). Processes featured in DGVMs include parameters which are prone to substantial uncertainty. To cope with these uncertainties Latin hypercube sampling (LHS) is used to create a 1000-member perturbed parameter ensemble, which is then evaluated with a diverse set of global and spatiotemporally resolved observational constraints. We discuss the performance of the constrained ensemble and use it to formulate a new best-guess version of the model (LPX-Bern v1.4). The observationally constrained ensemble is used to investigate historical emissions due to LULCC (ELUC) and their sensitivity to model parametrization. We find a global ELUC estimate of 158 (108, 211) PgC (median and 90 % confidence interval) between 1800 and 2016. We compare ELUC to other estimates both globally and regionally. Spatial patterns are investigated and estimates of ELUC of the 10 countries with the largest contribution to the flux over the historical period are reported. We consider model versions with and without additional land-use processes (shifting cultivation and wood harvest) and find that the difference in global ELUC is on the same order of magnitude as parameter-induced uncertainty and in some cases could potentially even be offset with appropriate parameter choice.

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