MAgPIE - An Open Source land-use modeling framework

4.8.2

created with goxygen 1.4.4

Peatland (58_peatland)

Description

The peatland module calculates GHG emissions from degrading/drained peatlands.

Interfaces

Input

Output

Realizations

(A) off

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.

(B) v2

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 2022. Therefore, it is advised to set s58_fix_peatland to 2020 when using this realisation (2022 is not available as time step in MAgPIE). Future peatland dynamics are estimated by multiplying changes in managed land with a 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 and intact peatland have the same GHG emission factors, which avoids that intact is converted to rewetted peatland area.

Constraint for constant total peatland area over time:

\[\begin{multline*} \sum_{land58} v58\_peatland(j2,land58) = \sum_{land58} pc58\_peatland(j2,land58) \end{multline*}\]

Peatland area change:

\[\begin{multline*} v58\_peatlandChange(j2,land58) = v58\_peatland(j2,land58)-pc58\_peatland(j2,land58) \end{multline*}\]

Managed land area:

\[\begin{multline*} v58\_manLand(j2,manPeat58) = m58\_LandMerge(vm\_land,vm\_land\_forestry,"j2") \end{multline*}\]

Managed land area expansion and reduction:

\[\begin{multline*} v58\_manLandExp(j2,manPeat58) = m58\_LandMerge(vm\_landexpansion,vm\_landexpansion\_forestry,"j2") \end{multline*}\]

\[\begin{multline*} v58\_manLandRed(j2,manPeat58) = m58\_LandMerge(vm\_landreduction,vm\_landreduction\_forestry,"j2") \end{multline*}\]

Future peatland dynamics (v58_peatland) for drained peatlands used as cropland, pasture or forestry (manPeat58) depend on changes in managed agricultural and forestry land (v58_manLandExp, v58_manLandRed), multiplied with corresponding scaling factors for expansion (p58_scalingFactorExp) and reduction (p58_scalingFactorRed). Both scaling factors are time-dynamic, i.e. the scaling factors vary depending on changes in drained peatland and managed land. The scaling factor for expansion reflects the ratio of available area for peatland drainage and managed land expansion, based on the assumption that the expansion of drained peatland is proportional to the expansion of managed land. The scaling factor for reduction reflects the ratio of drained peatland and total peatland area, based on the assumption that the likelihood of peatland rewetting increases with a higher share of drained peatland over total peatland area. Therefore, the scaling factor for peatland reduction increases with an increasing share of drained peatland and decreases with a decreasing share of drained peatland. In case managed land remains unchanged, also drained peatland remains unchanged.

\[\begin{multline*} v58\_peatland(j2,manPeat58) = pc58\_peatland(j2,manPeat58) + v58\_manLandExp(j2,manPeat58) \cdot \sum_{ct} p58\_scalingFactorExp(ct,j2) - v58\_balance(j2,manPeat58) - v58\_manLandRed(j2,manPeat58) \cdot \sum_{ct} p58\_scalingFactorRed(ct,j2,manPeat58) + v58\_balance2(j2,manPeat58) \end{multline*}\]

Drained peatland used for agriculture and forestry cannot exceed corresponding managed land.

\[\begin{multline*} v58\_peatland(j2,manPeat58) \leq v58\_manLand(j2,manPeat58) \end{multline*}\]

Costs for peatland degradation and rewetting

\[\begin{multline*} vm\_peatland\_cost(j2) = \sum_{cost58} v58\_peatland\_cost\_annuity(j2,cost58) + v58\_peatland(j2,"rewetted") \cdot \sum_{ct} i58\_cost\_rewet\_recur(ct) + \sum_{manPeat58} v58\_peatland(j2,manPeat58) \cdot \sum_{ct} i58\_cost\_drain\_recur(ct) + \sum_{manPeat58}\left( v58\_balance(j2,manPeat58)+v58\_balance2(j2,manPeat58)\right) \cdot s58\_balance\_penalty \end{multline*}\]

\[\begin{multline*} v58\_peatland\_cost\_annuity(j2,cost58) \geq \left(- v58\_peatlandChange(j2,"intact") \cdot \sum_{ct} i58\_cost\_drain\_intact\_onetime(ct)\right)\$sameas(cost58,"drain\_intact") + \left(- v58\_peatlandChange(j2,"rewetted") \cdot \sum_{ct} i58\_cost\_drain\_rewet\_onetime(ct)\right)\$sameas(cost58,"drain\_rewetted") + \left(v58\_peatlandChange(j2,"rewetted") \cdot \sum_{ct} i58\_cost\_rewet\_onetime(ct)\right)\$sameas(cost58,"rewet") \cdot \sum_{cell(i2,j2),ct}\left(\frac{pm\_interest(ct,i2)}{\left(1+pm\_interest(ct,i2)\right)}\right) \end{multline*}\]

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

\[\begin{multline*} vm\_emissions\_reg(i2,"peatland",poll58) = \sum_{cell(i2,j2),land58,emisSub58\_to\_poll58(emisSub58,poll58)}\left( v58\_peatland\_emis(j2,land58,emisSub58)\right) \end{multline*}\]

Peatland scaling factor for expansion: (totalPeatland - manPeatland) / (totalLand - manLand)

• p58_availPeatlandExp = totalPeatland - manPeatland
• p58_availLandExp = totalLand - manLand

p58_availPeatlandExp(t,j) = sum(land58, pc58_peatland(j,land58)) - sum(manPeat58, pc58_peatland(j,manPeat58));
p58_availLandExp(t,j) = sum(land, pcm_land(j,land)) - sum(manPeat58, pc58_manLand(j,manPeat58));
p58_scalingFactorExp(t,j) = 
    (p58_availPeatlandExp(t,j) / p58_availLandExp(t,j))
    $(p58_availPeatlandExp(t,j) > 1e-4 AND p58_availLandExp(t,j) > 1e-4)
    + 0$(p58_availPeatlandExp(t,j) <= 1e-4 OR p58_availLandExp(t,j) <= 1e-4);
p58_scalingFactorExp(t,j)$(p58_scalingFactorExp(t,j) > 1) = 1; 

Peatland scaling factor for reduction: manPeatland / totalPeatland

p58_scalingFactorRed(t,j,manPeat58) = 
    (pc58_peatland(j,manPeat58) / sum(land58, pc58_peatland(j,land58)))
    $(pc58_peatland(j,manPeat58) > 1e-4 AND sum(land58, pc58_peatland(j,land58)) > 1e-4)
    + 0$(pc58_peatland(j,manPeat58) <= 1e-4 OR sum(land58, pc58_peatland(j,land58)) <= 1e-4);
p58_scalingFactorRed(t,j,manPeat58)$(p58_scalingFactorRed(t,j,manPeat58) > 1) = 1; 

Limitations Peatland area and GHG emissions are fixed to 2022 levels for the historic period, depending on s58_fix_peatland. Organic carbon stocks in peatlands are not accounted for.

Definitions

Objects

Sets

Authors

Florian Humpenöder, Debbora Leip

See Also

10_land, 11_costs, 12_interest_rate, 32_forestry, 45_climate, 56_ghg_policy

References