Gross Carbon Emissions

FeliX calculates associated gross emissions for each energy source directly from model predictions of primary energy demand and consumption. The plot below illustrates the contribution of each to total annual emissions, listing for convenience the specific values for 2010 and 2100. Overall, gross annual emissions are predicted to rise 66% between 2010 and 2100 in the BAU scenario.

Gross annual emissions in Pg C from land use and land use change; and combustion of coal, oil, gas, and renewable energies (biomass).

Gross annual emissions in Pg C from land use and land use change; and combustion of coal, oil, gas, and renewable energies (biomass).

Historical data from the Carbon Dioxide Information Analysis Center (CDIAC) is shown for land use change, coal, oil, and gas in bold for the period [1900,2005]. This data is used to validate model projections, not for calibration.

The table at right lists emissions intensities for each of the carbon-emitting fuels represented in the model. These are consensus figures, and are not tuned to achieve agreement between IEA energy data and CDIAC emissions figures.

Gross emissions from renewable energies are equivalent to 107% of the carbon stored in harvested biomass (50% carbon by mass plus a penalty per unit weight for agricultural input, harvesting, and transport). Net emissions are significantly reduced due to prior uptake of atmospheric carbon in biomass increments.

Land Use Emissions

Emissions from land use & land use change (LULUC) contribute to total annual emissions in the FeliX model. LULUC emissions include agricultural inputs--especially fertilizers--as well as deforestation.

Agricultural emissions, shown below in brown, are predicted to rise steadily through 2100 due to the expansion of agricultural land as well as increased use of fertilizers. This parameter is calibrated in the model to historical data on agricultural emissions from the FAO.

Carbon emissions [PgC/yr] from land use/land use change (LULUC) are represented by the shaded grey region. The specific contribution to LULUC emissions from agricultural land use (especially fertilizers) is calibrated to historical data from the FAO and shown in brown. The dark gray and brown shaded regions propagate the effects of high and low population estimates.

Carbon emissions [PgC/yr] from land use/land use change (LULUC) are represented by the shaded grey region. The specific contribution to LULUC emissions from agricultural land use (especially fertilizers) is calibrated to historical data from the FAO and shown in brown. The dark gray and brown shaded regions propagate the effects of high and low population estimates.

The second component of LULUC emissions is deforestation, which is determined endogenously in the model (is not calibrated to historical data). Deforestation is estimated to have contributed roughly 1 PgC in annual emissions for most of the period 1950-2000. For the next few decades, modest afforestation is predicted to partially offset agricultural emissions through the increase of forest carbon stocks.

Near the end of the century, however, competition for land is predicted to accelerate deforestation, resulting in a nearly-twofold increase in total LULUC emissions. This result is highly dependent on population estimates, as shown by the wide dark-grey shaded region.

Historical data from the CDIAC on total land use emissions is used as a check on model results. 

Forests & Plantations

Forest land is an area of major interest, and an important factor in the evaluation of energy, agricultural, and climate change policies. The tension among agricultural, forest, and "other" lands is central to the FeliX model and has been discussed here.

Model results and FAO data on total forest area. At bottom, the expansion of managed forests and plantations (by 2 orders of magnitude) is shown in lime green. The demarcated regions around the  Total Forest  and  Managed Forest  results indicate the consequences of high and low population scenarios.

Model results and FAO data on total forest area. At bottom, the expansion of managed forests and plantations (by 2 orders of magnitude) is shown in lime green. The demarcated regions around the Total Forest and Managed Forest results indicate the consequences of high and low population scenarios.

Shown above, total forest land is predicted to remain relatively stable at around 4 billion hectares through 2100. FAOSTAT historical data for the period [1990-2012] is also plotted. However, this general prediction belies several real threats to forest ecosystems and the valuable habitats they represent.

First, expansion of managed forests or plantations into formerly pristine areas replaces complex ecosystems with monocultures, with several important consequences: 

  1. Increased susceptibility to disease, climate change, drought, and invasive species
  2. Habitat destruction and biodiversity loss
  3. Potential soil degradation and carbon stock reduction

Secondly, through the current century, expansion of agricultural land is predicted to result in the destruction of nearly 700 million hectares of "other" natural habitats such as grasslands (discussed here). Though the model does not assign this burden to forests, they are vulnerable to being cleared for profit or even in the pursuit of food security. To wit, the high population scenario does predict both 10% deforestation and heightened demand for plantations by 2100.

Thirdly (and relatedly), forest area predictions are heavily dependent on agricultural yields. If yields fail to keep up with population growth, rising food demand (especially animal products) will make cleared land (i.e. pasture) more valuable even than heavily-managed forests. 

Deforestation rates are used in the calculation of land use change emissions

 

Agricultural Land

Land categorized as "agricultural" is subdivided into the following classes:

Schematic of Agricultural Land subdivisions in the model.       (Click to enlarge)

  • arable land
  • permanent crops
  • permanent meadows and pastures

Arable land and permanent crops can be used to produce food, feed, or energy crops, while permanent meadows and pastures are used only for feed production. The BAU scenario is calibrated to historical data available on FAOSTAT and shown in grey below.

Permanent pastures & meadows (top) and arable land & permanent crops (bottom) in the BAU scenario. 

Permanent pastures & meadows (top) and arable land & permanent crops (bottom) in the BAU scenario. 

As shown in the plot above and here, the model predicts an end to the steady expansion of agricultural land seen in the second half of the last century: through 2050, growth in demand for vegetal and animal products is likely to be satisfied by agricultural intensification (discussed here).

After midcentury, however, the cumulative effects of fertilizer saturation, water scarcity, and ozone pollution may cause a stagnation in agricultural yields. As demand for food (in particular, animal products) continues to grow, agricultural land may begin to expand indefinitely after 2050 at the expense of natural habitats.