Interactions between land use change and carbon cycle feedbacks

Abstract

Using the Community Earth System Model, 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. 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 CO 2 on photosynthesis in trees, and thus, model-projected carbon feedbacks are especially sensitive to deforestation.

The Land Use Model Intercomparison Project (LUMIP) contribution to CMIP6: rationale and experimental design

“…The LASC, which is an indirect LULCC flux, occurs when conversion of land from natural lands (forests) to managed lands (crops or pasture) reduces the capacity of the land biosphere to take up anthropogenic carbon dioxide in the future (e.g., Gitz and Ciais, 2003). While small historically it may be of the same order as the net LULCC flux without LASC for future scenarios of strong CO 2 in-crease (Gerber et al, 2013;Mahowald et al, 2016;Pongratz et al, 2014). The land-use carbon feedback can be assessed in emission-driven simulations where LULCC carbon fluxes alter the atmospheric CO 2 concentration and the land-use changes also affect the climate through biogeophysical responses, both of which can then feed back onto the productivity of both natural and managed vegetation.…”

Agroforestry Status and Its Role to Sequester Atmospheric Co2 Under Semi-Arid Climatic Conditions in Pakistan

“…If we continue on our present course, life on the Earth will be modified to such an extent that it will be very difficult to fix (IPCC, 2000; Mahowald et al, 2017). Due to several activities like combustion of fossil fuels and deforestation during the last 100 years, chemical makeup of this flimsy layer of the atmosphere has been extremely altered (Pold et al, 2017).…”

A Bayesian Ensemble Data Assimilation to Constrain Model Parameters and Land Use Carbon Emissions

“…However since these methods operate sequentially, the metric and relative weighting of observational products have to be chosen beforehand, which can prove difficult if multiple observational data sets are to be assimilated simultaneously. The assessment of the performance of a given model version using observational benchmarks has also been actively discussed in the literature (Hoffman et al, 2017;Peng et al, 2014;Kelley et al, 2013;Luo 15 et al, 2012;Blyth et al, 2011;Randerson et al, 2009) and different frameworks have been proposed. Here we employ the Latin Hypercube Sampling (LHS) (McKay et al, 1979) approach, as used successfully in previous studies Battaglia et al, 2016;Steinacher and Joos, 2016;Battaglia and Joos, 2017;Zaehle et al, 2005).…”

“…Furthermore, it can also be used in model intercomparison studies, where single realizations of different models are compared. benchmarking (Hoffman et al, 2017;Kelley et al, 2013;Luo et al, 2012;Blyth et al, 2011) by comparing different models or model versions graphically and using statistical metrics (Stow et al, 2009) to a broad and diverse range of observations.…”