The peatland module calculates GHG emissions from degrading/drained peatlands.
| Description | Unit | A | B | C | |
|---|---|---|---|---|---|
| pcm_land (j, land) |
Land area in previous time step including possible changes after optimization | \(10^6 ha\) | x | x | |
| pcm_land_forestry (j, type32) |
Forestry land | \(10^6 ha\) | x | ||
| pm_climate_class (j, clcl) |
Koeppen-Geiger climate classification on the simulation cluster level | \(1\) | x | x | |
| pm_interest (t_all, i) |
Interest rate in each region and timestep | \(\%/yr\) | x | x | |
| vm_emissions_reg (i, emis_source, pollutants) |
Regional emissions by source and gas after technical mitigation N CH4 C | \(Tg/yr\) | x | x | x |
| vm_land (j, land) |
Land area of the different land types | \(10^6 ha\) | x | x | |
| vm_land_forestry (j, type32) |
Forestry land | \(10^6 ha\) | x |
| Description | Unit | |
|---|---|---|
| vm_peatland_cost (j) |
One-time and recurring cost of managed peatland | \(10^6 USD_{05MER}/yr\) |
In this realization, peatlands do not exist. Therefore, GHG emissions from degrading peatlands are assumed zero.
Limitations Peatland area and associated GHG emissions are fixed to zero.
In this realization, the state of peatlands is modelled as described in Humpenöder et al. (2020). The initial map of peatland area consists of intact and degraded peatland area for the year 2015, based on Leifeld and Menichetti (2018) and the Global Peatland Database. Future peatland dynamics are estimated by scaling changes in managed land with the ratio of total peatland area and total land area (peatland scaling factor). GHG emissions from degraded and rewetted peatlands are calculated using IPCC wetland GHG emission factors from Hiraishi et al. (2014) and Wilson, Blain, and Couwenberg (2016).
Land transition matrix for peatland area. The sum of current peatland area defined in v58_lu_transitions has to equal the sum of peatland area in the previous time step (pc58_peatland_man + pc58_peatland_intact). The two balancing variables v58_balance_positive and v58_balance_negative are needed to avoid technical infeasibilities due to small differences in accuracy between variables and parameters in GAMS. The use of v58_balance_positive and v58_balance_negative is minimized by putting a high cost factor on these variables (q58_peatland_cost_full). In practice, v58_balance_positive and v58_balance_negativeshould deviate from zero only in exceptional cases.
\[\begin{multline*} \sum_{from58,to58} v58\_lu\_transitions(j2,from58,to58) + v58\_balance\_positive(j2) - v58\_balance\_negative(j2) = \sum_{man58,land58} pc58\_peatland\_man(j2,man58,land58) + pc58\_peatland\_intact(j2) \end{multline*}\]
\[\begin{multline*} \sum_{from58} v58\_lu\_transitions(j2,from58,to58) = v58\_peatland\_man(j2,"degrad","crop")\$sameas(to58,"degrad\_crop") + v58\_peatland\_man(j2,"degrad","past")\$sameas(to58,"degrad\_past") + v58\_peatland\_man(j2,"degrad","forestry")\$sameas(to58,"degrad\_forestry") + v58\_peatland\_man(j2,"unused","crop")\$sameas(to58,"unused\_crop") + v58\_peatland\_man(j2,"unused","past")\$sameas(to58,"unused\_past") + v58\_peatland\_man(j2,"unused","forestry")\$sameas(to58,"unused\_forestry") + v58\_peatland\_man(j2,"rewet","crop")\$sameas(to58,"rewet\_crop") + v58\_peatland\_man(j2,"rewet","past")\$sameas(to58,"rewet\_past") + v58\_peatland\_man(j2,"rewet","forestry")\$sameas(to58,"rewet\_forestry") + v58\_peatland\_intact(j2)\$sameas(to58,"intact") \end{multline*}\]
\[\begin{multline*} \sum_{to58} v58\_lu\_transitions(j2,from58,to58) = pc58\_peatland\_man(j2,"degrad","crop")\$sameas(from58,"degrad\_crop") + pc58\_peatland\_man(j2,"degrad","past")\$sameas(from58,"degrad\_past") + pc58\_peatland\_man(j2,"degrad","forestry")\$sameas(from58,"degrad\_forestry") + pc58\_peatland\_man(j2,"unused","crop")\$sameas(from58,"unused\_crop") + pc58\_peatland\_man(j2,"unused","past")\$sameas(from58,"unused\_past") + pc58\_peatland\_man(j2,"unused","forestry")\$sameas(from58,"unused\_forestry") + pc58\_peatland\_man(j2,"rewet","crop")\$sameas(from58,"rewet\_crop") + pc58\_peatland\_man(j2,"rewet","past")\$sameas(from58,"rewet\_past") + pc58\_peatland\_man(j2,"rewet","forestry")\$sameas(from58,"rewet\_forestry") + pc58\_peatland\_intact(j2)\$sameas(from58,"intact") \end{multline*}\]
The following two equations calculate land expansion and land contraction based on the above land transition matrix.
\[\begin{multline*} v58\_expansion(j2,to58) = \sum_{from58\$\left(not sameas(from58,to58)\right)}\left( v58\_lu\_transitions(j2,from58,to58)\right) \end{multline*}\]
\[\begin{multline*} v58\_reduction(j2,from58) = \sum_{to58\$\left(not sameas(from58,to58)\right)}\left( v58\_lu\_transitions(j2,from58,to58)\right) \end{multline*}\]
Future peatland degradation (v58_peatland_man) depends on managed land (vm_land), scaled with the ratio of total peatland area and total land area (p58_scaling_factor) and a calibration factor (p58_calib_factor) for alignment with historic levels of degraded peatland. By multiplying changes in managed land (vm_land) with the scaling factor we implicitly assume that intact peatlands are distributed equally within a grid cell. The following example illustrates the mechanism used for projecting peatland dynamics: In a given grid cell, the total land area is 50 Mha and the total peatland area is 10 Mha. Therefore, the scaling factor is 0.2 (10 Mha divided by 50 Mha). If cropland expands by 5 Mha, 1 Mha of intact peatland is converted to degraded peatland (5 Mha x 0.2). If the total cell would become cropland, degraded peatland would equal to the total peatland area (50 Mha x 0.2 = 10 Mha).
\[\begin{multline*} v58\_peatland\_man(j2,"degrad",land58) = vm\_land(j2,land58) \cdot p58\_scaling\_factor(j2) \cdot p58\_calib\_factor(j2,land58) \end{multline*}\]
This constraint avoids the conversion of intact peatland into rewetted peatland.
\[\begin{multline*} \sum_{stat\_rewet58} v58\_expansion(j2,stat\_rewet58) \leq \sum_{stat\_degrad58}\left( v58\_reduction(j2,stat\_degrad58) + v58\_expansion(j2,stat\_degrad58)\right) - v58\_reduction(j2,"intact") \end{multline*}\]
Costs for peatland degradation and rewetting
\[\begin{multline*} vm\_peatland\_cost(j2) = v58\_peatland\_cost(j2) + \left(v58\_balance\_positive(j2) + v58\_balance\_negative(j2)\right) \cdot s58\_cost\_balance \end{multline*}\]
\[\begin{multline*} v58\_peatland\_cost(j2) = v58\_peatland\_cost\_annuity(j2) + \sum_{land58} v58\_peatland\_man(j2,"rewet",land58) \cdot \sum_{ct} i58\_cost\_rewet\_recur(ct) + \sum_{degrad58,land58} v58\_peatland\_man(j2,degrad58,land58) \cdot \sum_{ct} i58\_cost\_degrad\_recur(ct) \end{multline*}\]
\[\begin{multline*} v58\_peatland\_cost\_annuity(j2) = \left(\sum_{stat\_rewet58} v58\_expansion(j2,stat\_rewet58) \cdot \sum_{ct} i58\_cost\_rewet\_onetime(ct) + \left(v58\_reduction(j2,"intact") + \sum_{stat\_rewet58} v58\_reduction(j2,stat\_rewet58)\right) \cdot \sum_{ct} i58\_cost\_degrad\_onetime(ct)\right) \cdot \sum_{cell(i2,j2),ct}\left(\frac{pm\_interest(ct,i2)}{\left(1+pm\_interest(ct,i2)\right)}\right) \end{multline*}\]
GHG emissions from managed peatlands (degraded and rewetted)
\[\begin{multline*} v58\_peatland\_emis(j2,emis58) = \sum_{man58,land58,clcl58}\left( v58\_peatland\_man(j2,man58,land58) \cdot p58\_mapping\_cell\_climate(j2,clcl58) \cdot p58\_ipcc\_wetland\_ef(clcl58,land58,emis58,man58)\right) \end{multline*}\]
Conversion from CO2 equivalent to element unit for interface vm_emissions_reg using GWP100 conversion factors from AR5 (same as in Wilson, Blain, and Couwenberg (2016)).
\[\begin{multline*} vm\_emissions\_reg(i2,"peatland",poll58) = \sum_{cell(i2,j2),emisSub58\_to\_poll58(emisSub58,poll58)}\left( v58\_peatland\_emis(j2,emisSub58) \cdot p58\_conversion\_factor(emisSub58)\right) \end{multline*}\]
Limitations Peatland area and GHG emissions are fixed to 2015 levels for the historic period, depending on
s58_fix_peatland. Organic carbon stocks in peatlands are not accounted for.
In this realization, the state of peatlands is modelled based on the methodology described in Humpenöder et al. (2020).
The initial map for intact, degraded and rewetted peatland is based on the Global Peatland Map 2.0 and the Global Peatland Database, both for the year 2020. Therefore, it is advised to set s58_fix_peatland to 2020 when using this realisation. Future peatland dynamics are estimated by scaling changes in managed land with the ratio of total peatland area and total land area (peatland scaling factor). GHG emissions from drained and rewetted peatlands as well as from peat extraction are calculated based on GHG emission factors. In this realisation, peatland GHG emission factors for boreal and tropical climates are based on Hiraishi et al. (2014) and Wilson, Blain, and Couwenberg (2016). Peatland GHG emission factors for temperate climates are based on more recent estimates from Tiemeyer et al. (2020). Assumed rules for changes in peatland area: Sum over total peatland area (degraded, intact, rewetted) is assumed constant. Intact peatland area can only decrease. Degraded peatland area (crop, past, forestry and unused) depends on managed land. Area for peat extraction (peatExtract) is fixed. Rewetted peatland area can only increase if degraded peatland area declines and intact peatland area remains constant.
Constraint for constant total peatland area:
\[\begin{multline*} \sum_{land58} v58\_peatland(j2,land58) = \sum_{land58} pc58\_peatland(j2,land58) \end{multline*}\]
Constraints for peatland area expansion and reduction:
\[\begin{multline*} v58\_expansion(j2,land58) \geq v58\_peatland(j2,land58)-pc58\_peatland(j2,land58) \end{multline*}\]
\[\begin{multline*} v58\_reduction(j2,land58) \geq pc58\_peatland(j2,land58)-v58\_peatland(j2,land58) \end{multline*}\]
Future peatland degradation (v58_peatland) depends on managed land (vm_land, vm_land_forestry), scaled with the ratio of total peatland area and total land area (p58_scaling_factor). By multiplying changes in managed land with the scaling factor we implicitly assume that intact peatlands are distributed equally within a grid cell. The following example illustrates the mechanism used for projecting peatland dynamics: In a given grid cell, the total land area is 50 Mha and the total peatland area is 10 Mha. Therefore, the scaling factor is 0.2 (10 Mha divided by 50 Mha). If cropland expands by 5 Mha, 1 Mha of intact peatland is converted to degraded peatland (5 Mha x 0.2). If the total cell would become cropland, degraded peatland would equal to the total peatland area (50 Mha x 0.2 = 10 Mha).
\[\begin{multline*} v58\_peatland(j2,"crop") = pc58\_peatland(j2,"crop") + \left(\left(vm\_land(j2,"crop")-pcm\_land(j2,"crop")\right) \cdot p58\_scaling\_factor(j2)\right) \end{multline*}\]
\[\begin{multline*} v58\_peatland(j2,"past") = pc58\_peatland(j2,"past") + \left(\left(vm\_land(j2,"past")-pcm\_land(j2,"past")\right) \cdot p58\_scaling\_factor(j2)\right) \end{multline*}\]
\[\begin{multline*} v58\_peatland(j2,"forestry") = pc58\_peatland(j2,"forestry") + \left(\left(vm\_land\_forestry(j2,"plant")-pcm\_land\_forestry(j2,"plant")\right) \cdot p58\_scaling\_factor(j2)\right) \end{multline*}\]
This constraint avoids the conversion of intact peatland into rewetted peatland. In each cluster, rewetted peatland area can only increase if no intact peatland area is lost. Therefore, rewetted peatland area can only increase if degraded peatland area (landDrained58) declines.
\[\begin{multline*} v58\_expansion(j2,"rewetted") \cdot v58\_reduction(j2,"intact") = 0 \end{multline*}\]
Costs for peatland degradation and rewetting
\[\begin{multline*} vm\_peatland\_cost(j2) = v58\_peatland\_cost(j2) \end{multline*}\]
\[\begin{multline*} v58\_peatland\_cost(j2) = v58\_peatland\_cost\_annuity(j2) + v58\_peatland(j2,"rewetted") \cdot \sum_{ct} i58\_cost\_rewet\_recur(ct) + \sum_{landDrainedUsed58} v58\_peatland(j2,landDrainedUsed58) \cdot \sum_{ct} i58\_cost\_degrad\_recur(ct) \end{multline*}\]
\[\begin{multline*} v58\_peatland\_cost\_annuity(j2) = \left(v58\_expansion(j2,"rewetted") \cdot \sum_{ct} i58\_cost\_rewet\_onetime(ct) + v58\_reduction(j2,"intact") \cdot \sum_{ct} i58\_cost\_degrad\_onetime(ct)\right) \cdot \sum_{cell(i2,j2),ct}\left(\frac{pm\_interest(ct,i2)}{\left(1+pm\_interest(ct,i2)\right)}\right) \end{multline*}\]
Detailed peatland GHG emissions
\[\begin{multline*} v58\_peatland\_emis(j2,land58,emis58) = \sum_{clcl58}\left( v58\_peatland(j2,land58) \cdot p58\_mapping\_cell\_climate(j2,clcl58) \cdot f58\_ipcc\_wetland\_ef(clcl58,land58,emis58)\right) \end{multline*}\]
Aggregation of detailed peatland GHG emissions for interface vm_emissions_reg
\[\begin{multline*} vm\_emissions\_reg(i2,"peatland",poll58) = \sum_{cell(i2,j2),land58,emisSub58\_to\_poll58(emisSub58,poll58)}\left( v58\_peatland\_emis(j2,land58,emisSub58)\right) \end{multline*}\]
Limitations Peatland area and GHG emissions are fixed to 2015/2020 levels for the historic period, depending on
s58_fix_peatland. Organic carbon stocks in peatlands are not accounted for.
| Description | Unit | A | B | C | |
|---|---|---|---|---|---|
| f58_ipcc_wetland_ef (clcl58, land58, emis58, ef58) |
Wetland GWP100 emission factors | \(t CO2eq/ha\) | x | x | |
| f58_peatland_area (j, land58) |
Peatland area | \(10^6 ha\) | x | ||
| f58_peatland_degrad (j) |
Degrading peatland area | \(10^6 ha\) | x | ||
| f58_peatland_intact (j) |
Intact peatland area | \(10^6 ha\) | x | ||
| i58_cost_degrad_onetime (t) |
One-time costs for peatland degradation | \(USD_{05MER}/ha\) | x | x | |
| i58_cost_degrad_recur (t) |
Recurring costs for degraded peatland | \(USD_{05MER}/ha\) | x | x | |
| i58_cost_rewet_onetime (t) |
One-time costs for peatland restoration | \(USD_{05MER}/ha\) | x | x | |
| i58_cost_rewet_recur (t) |
Recurring costs for rewetted peatland | \(USD_{05MER}/ha\) | x | x | |
| p58_calib_factor (j, land58) |
Calibration factor for managed peatland | \(1\) | x | ||
| p58_conversion_factor (emisSub58) |
Conversion factor from GWP100 GHG emissions to element | \(1\) | x | ||
| p58_ipcc_wetland_ef (clcl58, land58, emis58, man58) |
Wetland GWP100 emission factors | \(t CO2eq/ha\) | x | ||
| p58_man_land_area (j) |
Total managed land | \(10^6 ha\) | x | ||
| p58_mapping_cell_climate (j, clcl58) |
Mapping between cells and climate regions | \(binary\) | x | x | |
| p58_peatland_degrad (j) |
Intermediate calculation in peatland initialization | \(10^6 ha\) | x | ||
| p58_peatland_degrad_weight (j, land58) |
Weight for peatland distribution to land58 | \(1\) | x | ||
| p58_scaling_factor (j) |
Scaling factor for managed peatland | \(1\) | x | x | |
| pc58_peatland (j, land58) |
Peatland area | \(10^6 ha\) | x | ||
| pc58_peatland_intact (j) |
Intact peatland | \(10^6 ha\) | x | ||
| pc58_peatland_man (j, man58, land58) |
Managed peatland | \(10^6 ha\) | x | ||
| q58_expansion (j, to58) |
Peatland expansion | \(10^6 ha\) | x | x | |
| q58_peatland (j) |
Constraint for peatland area | \(10^6 ha\) | x | ||
| q58_peatland_cost (j) |
One-time and recurring cost of peatland conversion and management | \(10^6 USD_{05MER}/yr\) | x | x | |
| q58_peatland_cost_annuity (j) |
Annuity costs of peatland conversion in the current timestep | \(10^6 USD_{05MER}/yr\) | x | x | |
| q58_peatland_cost_full (j) |
One-time and recurring cost of peatland conversion and management including artifical balance cost | \(10^6 USD_{05MER}/yr\) | x | x | |
| q58_peatland_crop (j) |
Degraded peatland used as cropland | \(10^6 ha\) | x | ||
| q58_peatland_degrad (j, land58) |
Constraint for peatland degradation | \(10^6 ha\) | x | ||
| q58_peatland_emis (i, poll58) |
GHG emissions from managed peatland | \(Tg/yr\) | x | x | |
| q58_peatland_emis_detail (j, emis58) |
Detailed GHG emissions from managed peatland | \(t CO2eq/year\) | x | x | |
| q58_peatland_forestry (j) |
Degraded peatland used for forestry | \(10^6 ha\) | x | ||
| q58_peatland_past (j) |
Degraded peatland used as pasture | \(10^6 ha\) | x | ||
| q58_peatland_rewet (j) |
Constraint for peatland rewetting | \(10^6 ha\) | x | x | |
| q58_reduction (j, from58) |
Peatland reduction | \(10^6 ha\) | x | x | |
| q58_transition_from (j, from58) |
Peatland transitions from | \(10^6 ha\) | x | ||
| q58_transition_matrix (j) |
Peatland transitions | \(10^6 ha\) | x | ||
| q58_transition_to (j, to58) |
Peatland transitions to | \(10^6 ha\) | x | ||
| s58_cost_balance | Artificial cost for balance variable | \(USD_{05MER}/ha\) | x | x | |
| s58_cost_degrad_onetime | One-time costs for peatland degradation | \(USD_{05MER}/ha\) | x | x | |
| s58_cost_degrad_recur | Recurring costs for degraded peatland | \(USD_{05MER}/ha\) | x | x | |
| s58_cost_rewet_onetime | One-time costs for peatland restoration | \(USD_{05MER}/ha\) | x | x | |
| s58_cost_rewet_recur | Recurring costs for rewetted peatland | \(USD_{05MER}/ha\) | x | x | |
| s58_fix_peatland | Year indicating until when peatland area should be fixed to 2015 levels | \(year\) | x | x | |
| s58_rewetting_switch | Peatland rewetting on (Inf) or off | \(0\) | x | x | |
| v58_balance_negative (j) |
Balance variable for peatland transitions | \(10^6 ha\) | x | ||
| v58_balance_positive (j) |
Balance variable for peatland transitions | \(10^6 ha\) | x | ||
| v58_expansion (j, stat58) |
Peatland expansion | \(10^6 ha\) | x | x | |
| v58_lu_transitions (j, from58, to58) |
Peatland transitions | \(10^6 ha\) | x | ||
| v58_peatland (j, land58) |
Managed peatland | \(10^6 ha\) | x | ||
| v58_peatland_cost (j) |
One-time and recurring cost of managed peatland | \(10^6 USD_{05MER}/yr\) | x | x | |
| v58_peatland_cost_annuity (j) |
Annuity costs of managed peatland expansion in the current timestep | \(10^6 USD_{05MER}/yr\) | x | x | |
| v58_peatland_emis (j, emis58) |
Detailed GHG emissions from managed peatland | \(t CO2eq/year\) | x | x | |
| v58_peatland_intact (j) |
Intact peatland | \(10^6 ha\) | x | ||
| v58_peatland_man (j, man58, land58) |
Managed peatland | \(10^6 ha\) | x | ||
| v58_reduction (j, stat58) |
Peatland reduction | \(10^6 ha\) | x | x |
| description | |
|---|---|
| cell(i, j) | number of LPJ cells per region i |
| clcl | climate classification types |
| clcl_mapping(clcl, clcl58) | Mapping between detailed and simple climate classes |
| clcl58 | simple climate classes |
| ct(t) | Current time period |
| degrad58(man58) | State of degraded peatland |
| ef58(man58) | Peatland emissions factors |
| emis_source | Emission sources |
| emis58 | Wetland emission types |
| emisSub58_to_poll58(emisSub58, poll58) | Mapping |
| emisSub58(emis58) | Wetland emission types |
| factors | factors included in factor requirements |
| i | all economic regions |
| i2(i) | World regions (dynamic set) |
| j | number of LPJ cells |
| j2(j) | Spatial Clusters (dynamic set) |
| land | Land pools |
| land58(land) | Managed land types |
| landDrained58(land58) | Peatland land types |
| landDrainedUsed58(land58) | Peatland land types |
| man58 | State of managed peatland |
| poll58(pollutants) | Wetland emissions that can be taxed |
| pollutants(pollutants_all) | subset of pollutants_all that can be taxed |
| stat_degrad58(stat58) | Peatland status degrad |
| stat_man58(stat58) | Peatland status managed land |
| stat_rewet58(stat58) | Peatland status rewet |
| stat58 | Peatland status |
| t_all(t_ext) | 5-year time periods |
| t(t_all) | Simulated time periods |
| type | GAMS variable attribute used for the output |
| type32 | plantation type |
Florian Humpenöder
10_land, 11_costs, 12_interest_rate, 32_forestry, 45_climate, 56_ghg_policy