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Title: Interactions between land use change and carbon cycle feedbacks: Land Use and Carbon Cycle Feedbacks

Abstract

We explore the role of human land use and land cover change (LULCC) in modifying the terrestrial carbon budget in simulations forced by Representative Concentration Pathway 8.5, extended to year 2300 by using the Community Earth System Model, . Overall, conversion of land (e.g., from forest to croplands via deforestation) results in a model-estimated, cumulative carbon loss of 490 Pg C between 1850 and 2300, larger than the 230 Pg C loss of carbon caused by climate change over this same interval. The LULCC carbon loss is a combination of a direct loss at the time of conversion and an indirect loss from the reduction of potential terrestrial carbon sinks. Approximately 40% of the carbon loss associated with LULCC in the simulations arises from direct human modification of the land surface; the remaining 60% is an indirect consequence of the loss of potential natural carbon sinks. Because of the multicentury carbon cycle legacy of current land use decisions, a globally averaged amplification factor of 2.6 must be applied to 2015 land use carbon losses to adjust for indirect effects. This estimate is 30% higher when considering the carbon cycle evolution after 2100. Most of the terrestrial uptake of anthropogenic carbonmore » in the model occurs from the influence of rising atmospheric CO 2 on photosynthesis in trees, and thus, model-projected carbon feedbacks are especially sensitive to deforestation.« less

Authors:
 [1];  [2];  [3];  [3];  [4];  [3];  [1];  [5];  [1];  [5];  [3];  [6]
  1. Cornell Univ., Ithaca, NY (United States)
  2. Univ. of California, Irvine, CA (United States)
  3. National Center for Atmospheric Research, Boulder, CO (United States)
  4. Woods Hole Oceanographic Inst., Woods Hole, MA (United States)
  5. (United States)
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1376543
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Global Biogeochemical Cycles
Additional Journal Information:
Journal Volume: 31; Journal Issue: 1; Journal ID: ISSN 0886-6236
Publisher:
American Geophysical Union (AGU)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES

Citation Formats

Mahowald, Natalie M., Randerson, James T., Lindsay, Keith, Munoz, Ernesto, Doney, Scott C., Lawrence, Peter, Schlunegger, Sarah, Princeton Univ., NJ, Ward, Daniel S., Princeton Univ., NJ, Lawrence, David, and Hoffman, Forrest M.. Interactions between land use change and carbon cycle feedbacks: Land Use and Carbon Cycle Feedbacks. United States: N. p., 2017. Web. doi:10.1002/2016GB005374.
Mahowald, Natalie M., Randerson, James T., Lindsay, Keith, Munoz, Ernesto, Doney, Scott C., Lawrence, Peter, Schlunegger, Sarah, Princeton Univ., NJ, Ward, Daniel S., Princeton Univ., NJ, Lawrence, David, & Hoffman, Forrest M.. Interactions between land use change and carbon cycle feedbacks: Land Use and Carbon Cycle Feedbacks. United States. doi:10.1002/2016GB005374.
Mahowald, Natalie M., Randerson, James T., Lindsay, Keith, Munoz, Ernesto, Doney, Scott C., Lawrence, Peter, Schlunegger, Sarah, Princeton Univ., NJ, Ward, Daniel S., Princeton Univ., NJ, Lawrence, David, and Hoffman, Forrest M.. Mon . "Interactions between land use change and carbon cycle feedbacks: Land Use and Carbon Cycle Feedbacks". United States. doi:10.1002/2016GB005374. https://www.osti.gov/servlets/purl/1376543.
@article{osti_1376543,
title = {Interactions between land use change and carbon cycle feedbacks: Land Use and Carbon Cycle Feedbacks},
author = {Mahowald, Natalie M. and Randerson, James T. and Lindsay, Keith and Munoz, Ernesto and Doney, Scott C. and Lawrence, Peter and Schlunegger, Sarah and Princeton Univ., NJ and Ward, Daniel S. and Princeton Univ., NJ and Lawrence, David and Hoffman, Forrest M.},
abstractNote = {We explore the role of human land use and land cover change (LULCC) in modifying the terrestrial carbon budget in simulations forced by Representative Concentration Pathway 8.5, extended to year 2300 by using the Community Earth System Model, . Overall, conversion of land (e.g., from forest to croplands via deforestation) results in a model-estimated, cumulative carbon loss of 490 Pg C between 1850 and 2300, larger than the 230 Pg C loss of carbon caused by climate change over this same interval. The LULCC carbon loss is a combination of a direct loss at the time of conversion and an indirect loss from the reduction of potential terrestrial carbon sinks. Approximately 40% of the carbon loss associated with LULCC in the simulations arises from direct human modification of the land surface; the remaining 60% is an indirect consequence of the loss of potential natural carbon sinks. Because of the multicentury carbon cycle legacy of current land use decisions, a globally averaged amplification factor of 2.6 must be applied to 2015 land use carbon losses to adjust for indirect effects. This estimate is 30% higher when considering the carbon cycle evolution after 2100. Most of the terrestrial uptake of anthropogenic carbon in the model occurs from the influence of rising atmospheric CO2 on photosynthesis in trees, and thus, model-projected carbon feedbacks are especially sensitive to deforestation.},
doi = {10.1002/2016GB005374},
journal = {Global Biogeochemical Cycles},
number = 1,
volume = 31,
place = {United States},
year = {Mon Jan 23 00:00:00 EST 2017},
month = {Mon Jan 23 00:00:00 EST 2017}
}

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  • Previous work has demonstrated the sensitivity of terrestrial net carbon exchange to disturbance history and land use patterns at the scale of individual sites or regions. Here we show the influence of land use and land cover dynamics over the historical period 1850-present on global-scale carbon, nutrient, water, and energy fluxes. We also explore the spatial and temporal details of interactions among land use and disturbance history, rising atmospheric carbon dioxide consentation, and increasing anthropogenic nitrogen deposition. Our simulations show that these interactions are significant, and that their importance grows over time, expressed as a fraction of the independent forcingmore » terms. We conclude with an analysis of the influence of these interactions on the sign and magnitude of global climate-carbon cycle feedbacks.« less
  • 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 10,607 Tg C release from land ecosystems to atmosphere. PAs had experiencedmore » 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 1,642 Tg 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.« less
  • A five-compartment model for carbon cycling in the world's terrestrial ecosystems, which includes a concise treatment of the releases of carbon and shifts in carbon storage due to forest clearing, is presented. The dynamics of the less abundant isotopes, /sup 13/C and /sup 14/C, are included in the model to allow interpretation of available isotopic time series. The sensitivity of the net carbon flux between the terrestrial component of the model and atmosphere to 10% variability in terrestrial rate coefficients and growth parameters is examined; for the particular case considered here, the variability in model response is approx. = 10%.more » Response of the model agrees reasonably well with observations of historical changes in the specific activity of /sup 14/C in the atmosphere. The model-calculated Suess effect in 1952 is 2%, and the time constant of the exponential decrease in atmospheric /sup 14/C following the weapons test ban is 14 yr. By adjusting the releases of carbon due to forest clearing, a fit of model response to /sup 13/C//sup 12/C tree-ring time series is derived. The resulting forest-clearing carbon release function rises to 2.5 Pg/yr by 1910 and remains constant to the present. Due to establishment of ground vegetation following clearing, the net carbon flux from the terrestrial biotic system to the atmosphere is less than the release due to clearing in some instances. To accommodate this net input to the atmosphere in addition to that due to fossil fuel combustion, the pre-industrial CO/sup 2/ concentration must be assumed to have been lower than is implied by extrapolating the modern instrument records backward in time. 50 references, 5 figures, 2 tables.« less
  • Inclusion of fundamental ecological interactions between carbon and nitrogen cycles in the land component of an atmosphere-ocean general circulation model (AOGCM) leads to decreased carbon uptake associated with CO{sub 2} fertilization, and increased carbon uptake associated with warming of the climate system. The balance of these two opposing effects is to reduce the fraction of anthropogenic CO{sub 2} predicted to be sequestered in land ecosystems. The primary mechanism responsible for increased land carbon storage under radiatively forced climate change is shown to be fertilization of plant growth by increased mineralization of nitrogen directly associated with increased decomposition of soil organicmore » matter under a warming climate, which in this particular model results in a negative gain for the climate-carbon feedback. Estimates for the land and ocean sink fractions of recent anthropogenic emissions are individually within the range of observational estimates, but the combined land plus ocean sink fractions produce an airborne fraction which is too high compared to observations. This bias is likely due in part to an underestimation of the ocean sink fraction. Our results show a significant growth in the airborne fraction of anthropogenic CO{sub 2} emissions over the coming century, attributable in part to a steady decline in the ocean sink fraction. Comparison to experimental studies on the fate of radio-labeled nitrogen tracers in temperate forests indicates that the model representation of competition between plants and microbes for new mineral nitrogen resources is reasonable. Our results suggest a weaker dependence of net land carbon flux on soil moisture changes in tropical regions, and a stronger positive growth response to warming in those regions, than predicted by a similar AOGCM implemented without land carbon-nitrogen interactions. We expect that the between-model uncertainty in predictions of future atmospheric CO{sub 2} concentration and associated anthropogenic climate change will be reduced as additional climate models introduce carbon-nitrogen cycle interactions in their land components.« less
  • The authors present results of a study in an intensively impacted and highly fragmented landscape in which they apply field-measured carbon (C) density values to land-use/land-cover (LU/LC) statistics to estimate the flux of C between terrestrial ecosystems and the atmosphere from the 1970s and 1990s. Carbon densities were assigned to common LU/LC classes on vegetation maps produced by Mexican governmental organizations and, by differencing areas and C pools, net C flux was calculated from the central highlands of Chiapas, Mexico, during a 16-year period. The total area of closed forests was reduced by half while degraded and fragmented forests expandedmore » 56% and cultivated land and pasture areas increased by 8% and 30%, respectively. Total mean C densities ranged from a high of 504 tons C/ha in the oak and evergreen cloud forests class to a low of 147 tons C/ha in the pasture class. The differences in total C densities among the various LU/LC classes were due to changes in biomass while soil organic matter C remained similar. The authors estimate that a total of 19.99 {times} 10{sup 6} tons C were released to the atmosphere during the period of time covered by the study, equal to approximately 34% of the 1975 vegetation C pool. The Chiapas highlands, while comprising just 0.3% of Mexico`s surface area, contributed 3% of the net national C emissions.« less