MAgPIE - An Open Source land-use modeling framework

4.4.0

created with goxygen 1.3.0

Natural Vegetation (35_natveg)

Description

The natural vegetation (natveg) land module is one of the land modules in MAgPIE (see also the other land modules: 30_crop, 31_past, 32_forestry, 34_urban). It calculates land and carbon stocks, as well as the biodiversity value, of natural vegetation, which consists of primary forest, secondary forest and other natural land. The module determines the availability of natural vegetation for land conversion.

Interfaces

Interfaces to other modules

Input

module inputs (A: dynamic_feb21)
  Description Unit A
fm_bii_coeff
(bii_class44, potnatveg)
bii coeff \(unitless\) x
fm_carbon_density
(t_all, j, land, c_pools)
LPJmL carbon density for land and carbon pools \(tC/ha\) x
fm_luh2_side_layers
(j, luh2_side_layers10)
luh2 side layers \(grid cell share\) x
im_plantedclass_ac
(j, ac)
Raw Distribution of ageclass in secondary forest as a proxy for planted forest \(10^6 ha\) x
pcm_land
(j, land)
Land area in previous time step \(10^6 ha\) x
pm_carbon_density_ac
(t_all, j, ac, ag_pools)
Above ground natveg carbon density for age classes and carbon pools \(tC/ha\) x
pm_land_start
(j, land)
Land initialization area \(10^6 ha\) x
pm_timber_yield
(t, j, ac, forest_land)
Forest growing stock \(tDM/ha/yr\) x
pm_timber_yield_initial
(j, ac, forest_land)
Initial Forest yield \(tDM/ha/yr\) x
sm_fix_SSP2 year until which all parameters are fixed to SSP2 values \(year\) x
sm_wood_density Representative wood density based on IPCC \(tDM/m3\) x
vm_bv
(j, landcover44, potnatveg)
biodiversity value for all land cover classes (unweighted) \(Mha\) x
vm_carbon_stock
(j, land, c_pools)
Carbon stock in vegetation soil and litter for different land types \(10^6 tC\) x
vm_land
(j, land)
Land area of the different land types \(10^6 ha\) x

Output

module outputs
  Description Unit
vm_cost_hvarea_natveg
(i)
Cost of harvesting natural vegetation \(10^6 USD\)
vm_landdiff_natveg Aggregated difference in natveg land compared to previous timestep \(10^6 ha\)
vm_prod_natveg
(j, land_natveg, kforestry)
Production of woody biomass from natural vegetation \(10^6 tDM/yr\)

Realizations

(A) dynamic_feb21

In the dynamic_may18 realization, land and carbon stock dynamics of natural vegetation are modeled endogenously. The initial spatial distribution of the sub-land-types primary forest, secondary forest and other natural land is based on the LUH2 data set (Hurtt et al. 2018). The realization includes 2 different kinds of land protection. a) Land protection based on the World Database on Protected Areas (WDPA) maintained by the International Union for Conservation of Nature (IUCN) and b) land protection based on national policies implemented (NPI) and nationally determined contributions to the Paris agreement (NDC) taken from individual country reports. Land protection based on WDPA is static over time, while the NPI/NDC polices ramp up until 2030 and are assumed constant thereafter. For WDPA the level of land protection is based on IUCN catI+II, which reflect areas currently under protection (e.g. strict nature reserves and national parks), and distributed equally across all sub-land-types (primary forest, secondary forest and other natural land). On top of the IUCN catI+II land protection, there are options to protect different conservation priority areas such as biodiversity hotspots (BH), centers of plant diversity (CBD), frontier forests (FF) and last of the wild (LW). NPI/NDC land protection polices are be applied on forest and other land, depending on individual country reports. Additionally, this module provides the ability to harvest natural vegetation for timber. Both wood and woodfuel can be produceed from primary and secondary forest but other land is only allowed to be harvested for woodfuel.

The interface vm_land provides aggregated natveg land pools (ac) to other modules.

\[\begin{multline*} vm\_land(j2,"secdforest") = \sum_{ac} v35\_secdforest(j2,ac) \end{multline*}\]

\[\begin{multline*} vm\_land(j2,"other") = \sum_{ac} v35\_other(j2,ac) \end{multline*}\]

Carbon stocks for primary forest, secondary forest or other natural land are calculated as the product of respective area and carbon density. Carbon stocks decline if the area decreases (e.g. due to cropland expansion into forests). In case of abandoned agricultural land (increase of other natural land), natural succession, represented by age-class growth, results in increasing carbon stocks.

\[\begin{multline*} vm\_carbon\_stock(j2,"primforest",ag\_pools) = vm\_land(j2,"primforest") \cdot \sum_{ct} fm\_carbon\_density(ct,j2,"primforest",ag\_pools) \end{multline*}\]

\[\begin{multline*} vm\_carbon\_stock(j2,"secdforest",ag\_pools) = \sum_{ac}\left( v35\_secdforest(j2,ac) \cdot \sum\left(ct, pm\_carbon\_density\_ac(ct,j2,ac,ag\_pools)\right)\right) \end{multline*}\]

\[\begin{multline*} vm\_carbon\_stock(j2,"other",ag\_pools) = \sum_{ac}\left( v35\_other(j2,ac) \cdot \sum\left(ct, pm\_carbon\_density\_ac(ct,j2,ac,ag\_pools)\right)\right) \end{multline*}\]

The biodiversity value (BV) of primary forest, secondary forest and other land is computed by multiplying their respective land area with bii coefficients, which depend on the age class and whether the potential natural vegetation forest or non-forest (luh2 side layers).

\[\begin{multline*} vm\_bv(j2,"primforest",potnatveg) = vm\_land(j2,"primforest") \cdot fm\_bii\_coeff("primary",potnatveg) \cdot fm\_luh2\_side\_layers(j2,potnatveg) \end{multline*}\]

\[\begin{multline*} vm\_bv(j2,"secdforest",potnatveg) = \sum_{bii\_class\_secd}\left( \sum\left(ac\_to\_bii\_class\_secd(ac,bii\_class\_secd), v35\_secdforest(j2,ac)\right) \cdot fm\_bii\_coeff(bii\_class\_secd,potnatveg)\right) \cdot fm\_luh2\_side\_layers(j2,potnatveg) \end{multline*}\]

\[\begin{multline*} vm\_bv(j2,"other",potnatveg) = \sum_{bii\_class\_secd}\left( \sum\left(ac\_to\_bii\_class\_secd(ac,bii\_class\_secd), v35\_other(j2,ac)\right) \cdot fm\_bii\_coeff(bii\_class\_secd,potnatveg)\right) \cdot fm\_luh2\_side\_layers(j2,potnatveg) \end{multline*}\]

NPI/NDC land protection policies are implemented as minium forest land and other land stock.

\[\begin{multline*} vm\_land(j2,"primforest") + vm\_land(j2,"secdforest") \geq \sum_{ct} p35\_min\_forest(ct,j2) \end{multline*}\]

\[\begin{multline*} vm\_land(j2,"other") \geq \sum_{ct} p35\_min\_other(ct,j2) \end{multline*}\]

The following technical calculations are needed for reducing differences in land-use patterns between time steps. The gross change in natural vegetation is calculated based on land expansion and land contraction of other land, and land reduction of primary and secondary forest. This information is then passed to the land module (10_land):

\[\begin{multline*} vm\_landdiff\_natveg = \sum_{j2,ac}\left( v35\_other\_expansion(j2,ac) + v35\_other\_reduction(j2,ac) + v35\_secdforest\_expansion(j2,ac) + v35\_secdforest\_reduction(j2,ac) + v35\_primforest\_reduction(j2)\right) \end{multline*}\]

\[\begin{multline*} v35\_other\_expansion(j2,ac\_est) = v35\_other(j2,ac\_est) - pc35\_other(j2,ac\_est) \end{multline*}\]

\[\begin{multline*} v35\_other\_reduction(j2,ac\_sub) = pc35\_other(j2,ac\_sub) - v35\_other(j2,ac\_sub) \end{multline*}\]

\[\begin{multline*} v35\_secdforest\_expansion(j2,ac\_est) = v35\_secdforest(j2,ac\_est) - pc35\_secdforest(j2,ac\_est) \end{multline*}\]

\[\begin{multline*} v35\_secdforest\_reduction(j2,ac\_sub) = pc35\_secdforest(j2,ac\_sub) - v35\_secdforest(j2,ac\_sub) \end{multline*}\]

\[\begin{multline*} v35\_primforest\_reduction(j2) = pcm\_land(j2,"primforest") - vm\_land(j2,"primforest") \end{multline*}\]

For natural forest, per-hectare harvesting costs are positive to make sure that older forest with higher growing stock is preferred over younger forest. To mimic the difficulties in accessing primary forest, per-hectare harvesting costs for primary forest are higher than for secondary forest. Harvesting costs are paid everytime natural vegetation is harvested. The “real” harvested area are received from the timber module 73_timber.

\[\begin{multline*} vm\_cost\_hvarea\_natveg(i2) = \sum_{ct,cell(i2,j2),ac\_sub} v35\_hvarea\_secdforest(j2,ac\_sub) \cdot s35\_timber\_harvest\_cost\_secdforest + \sum_{ct,cell(i2,j2),ac\_sub}\left( v35\_hvarea\_other\left(j2, ac\_sub\right)\right) \cdot s35\_timber\_harvest\_cost\_other + \sum_{ct,cell(i2,j2)} v35\_hvarea\_primforest(j2) \cdot s35\_timber\_harvest\_cost\_primforest \end{multline*}\]

Woody biomass production from secondary forests is calculated by multiplying the area under production with corresponding yields of secondary forests, divided by the timestep length.

\[\begin{multline*} \sum_{kforestry} vm\_prod\_natveg(j2,"secdforest",kforestry) = \frac{ \sum_{ac\_sub}\left( v35\_hvarea\_secdforest(j2,ac\_sub) \cdot \sum\left(ct,pm\_timber\_yield(ct,j2,ac\_sub,"secdforest")\right)\right) }{ m\_timestep\_length\_forestry} \end{multline*}\]

Woody biomass production from primary forests is calculated by multiplying the area under production with corresponding yields of primary forests, divided by the timestep length.

\[\begin{multline*} \sum_{kforestry} vm\_prod\_natveg(j2,"primforest",kforestry) = v35\_hvarea\_primforest(j2) \cdot \frac{ \sum_{ct} pm\_timber\_yield(ct,j2,"acx","primforest") }{ m\_timestep\_length\_forestry} \end{multline*}\]

Wood-fuel production from other land is calculated by multiplying the area under production with corresponding yields of other land, divided by the timestep length. Wood production from other landis not allowed.

\[\begin{multline*} vm\_prod\_natveg(j2,"other","woodfuel") = \frac{ \sum_{ac\_sub}\left( v35\_hvarea\_other(j2,ac\_sub) \cdot \sum\left(ct, pm\_timber\_yield(ct,j2,ac\_sub,"other")\right)\right) }{ m\_timestep\_length\_forestry } \end{multline*}\]

Following equations show the harvested area from natural vegetation i.e. primary forests, secondary forests and other land. Important to note here that no wood production should be realized from other land. Harvested area for production purposes can be lower oe equal than land reduction in natural vegetation as not all lost area is (or should be) used for production.

\[\begin{multline*} v35\_hvarea\_secdforest(j2,ac\_sub) \leq v35\_secdforest\_reduction(j2,ac\_sub) \end{multline*}\]

\[\begin{multline*} v35\_hvarea\_primforest(j2) \leq v35\_primforest\_reduction(j2) \end{multline*}\]

\[\begin{multline*} v35\_hvarea\_other(j2,ac\_sub) \leq v35\_other\_reduction(j2,ac\_sub) \end{multline*}\]

Harvested secondary forest is still considered secondary forests due to restrictive NPI definitions. Also primary forest harvested will be considered to be secondary forest i.e., harvested primary forest gets reclassified as secondary forest and ends up in the youngest age-class (and follows regrowth)

\[\begin{multline*} \sum_{ac\_est} v35\_secdforest(j2,ac\_est) = \sum_{ac\_sub}v35\_hvarea\_secdforest(j2,ac\_sub) + v35\_hvarea\_primforest(j2) \end{multline*}\]

Harvested other land is still considered other land

\[\begin{multline*} \sum_{ac\_est} v35\_other(j2,ac\_est) \geq \sum_{ac\_sub}v35\_hvarea\_other(j2,ac\_sub) \end{multline*}\]

The following two constraints distribute additions to secdforest and other land over ac_est, which depends on the time step length (e.g. ac0 and ac5 for a 10 year time step).

\[\begin{multline*} v35\_secdforest(j2,ac\_est) = \frac{ \sum_{ac\_est2} v35\_secdforest(j2,ac\_est2)}{card(ac\_est2)} \end{multline*}\]

\[\begin{multline*} v35\_other(j2,ac\_est) = \frac{ \sum_{ac\_est2} v35\_other(j2,ac\_est2)}{card(ac\_est2)} \end{multline*}\]

If the vegetation carbon density in a simulation unit due to regrowth exceeds a threshold of 20 tC/ha the respective area is shifted from other natural land to secondary forest.

p35_recovered_forest(t,j,ac)$(not sameas(ac,"acx")) =
            p35_other(t,j,ac)$(pm_carbon_density_ac(t,j,ac,"vegc") > 20);
p35_other(t,j,ac) = p35_other(t,j,ac) - p35_recovered_forest(t,j,ac);
p35_secdforest(t,j,ac) =
            p35_secdforest(t,j,ac) + p35_recovered_forest(t,j,ac);

Limitations Initialization of both primary and secondary forest in highest age class or equal distrivution of such areas in all age classes. Data exists on a more emperically obtained distribution in different age classes based on satellite data but this results is highly negative land-use change emissions. Inclusion of this data in MAgPIE remains work in progess and is not available for release yet. Additionally, in this module realizatuion, harvested secondary forest stays secondary forest and harvested primary forest is reclassified as secondary forest.

Definitions

Objects

module-internal objects (A: dynamic_feb21)
  Description Unit A
f35_forest_disturbance_share
(i)
Share of area damanged by forest disturbances \(1\) x
f35_forest_lost_share
(i, driver_source)
Share of area damanged by forest fires \(1\) x
f35_gs_relativetarget
(i)
Relative growing stock target in each region \(m3/ha\) x
f35_land_iso
(t_ini10, iso, land)
Land area for different land pools at ISO level \(10^6 ha\) x
f35_min_land_stock
(t_all, j, pol35, pol_stock35)
Land protection policies [minimum land stock] \(Mha\) x
f35_protect_area
(j, prot_type)
Conservation priority areas \(10^6 ha\) x
f35_protection_fader
(t_all, prot_target35)
Protection scenario fader \(1\) x
i35_land_iso
(iso)
Total land area at ISO level \(10^6 ha\) x
i35_other
(j, ac)
Initial other land \(10^6 ha\) x
i35_plantedclass_ac
(j, ac)
Area of age-classes in secondary forest \(1\) x
i35_secdforest
(j, ac)
Initial secdforest \(10^6 ha\) x
p35_carbon_density_other
(t, j, ac, ag_pools)
Carbon density other land \(tC/ha\) x
p35_carbon_density_secdforest
(t, j, ac, ag_pools)
Carbon density secdforest \(tC/ha\) x
p35_country_dummy
(iso)
Dummy parameter indicating whether country is affected by selected land protection policy \(1\) x
p35_disturbance_loss_primf
(t, j)
Loss due to disturbances in primary forest \(10^6 ha\) x
p35_disturbance_loss_secdf
(t, j, ac)
Loss due to disturbances in secondary forest \(10^6 ha\) x
p35_gs_scaling_reg
(i)
Regional calibration factors for natural vegetation yields \(1\) x
p35_land
(t, j, land_natveg, ac)
Natural vegetation area \(10^6 ha\) x
p35_land_start_ac
(j, ac, land_natveg)
Initial Natural vegetation area \(10^6 ha\) x
p35_min_forest
(t, j)
Minimum forest stock [land protection policies] \(Mha\) x
p35_min_other
(t, j)
Minimum other land stock [land protection policies] \(Mha\) x
p35_observed_gs_reg
(i)
Observed growing stock in natural forests before calibration \(m3/ha\) x
p35_other
(t, j, ac)
Other land per age class \(10^6 ha\) x
p35_poulter_dist
(j, ac)
Share of age-classes in secondary forest \(1\) x
p35_protect_shr
(t, j, prot_type_all, land_natveg)
Land protection share for primforest secdforest and other land \(1\) x
p35_protect_shr_ini
(j, prot_type_all)
Land protection share for primforest secdforest and other land \(1\) x
p35_recovered_forest
(t, j, ac)
Recovered forest \(10^6 ha\) x
p35_region_prot_shr
(i)
Land protection share of the region \(1\) x
p35_save_dist
(j, ac)
Distribution of secondary forest saving \(1\) x
p35_save_natveg
(t, j, land_natveg)
Land protection for primforest secdforest and other land \(10^6 ha\) x
p35_secdforest
(t, j, ac)
Secdforest per age class \(10^6 ha\) x
p35_updated_gs_natfor
(t, i)
Updated growing stock in natural forests after calibration \(m3/ha\) x
pc35_other
(j, ac)
Other land per age class in current time step \(10^6 ha\) x
pc35_secdforest
(j, ac)
Secdforest per age class in current time step \(10^6 ha\) x
q35_bv_other
(j, potnatveg)
Biodiversity value of other land \(Mha\) x
q35_bv_primforest
(j, potnatveg)
Biodiversity value of primary forest \(Mha\) x
q35_bv_secdforest
(j, potnatveg)
Biodiversity value of secondary forest \(Mha\) x
q35_carbon_other
(j, ag_pools)
Other land carbon stock calculation \(10^6 tC\) x
q35_carbon_primforest
(j, ag_pools)
Primforest carbon stock calculation \(10^6 tC\) x
q35_carbon_secdforest
(j, ag_pools)
Secdforest carbon stock calculation \(10^6 tC\) x
q35_cost_hvarea
(i)
Cost of harvesting natural vegetation \(10^6 USD\) x
q35_hvarea_other
(j, ac)
Harvested area other land \(10^6 ha\) x
q35_hvarea_primforest
(j)
Harvested area primforest \(10^6 ha\) x
q35_hvarea_secdforest
(j, ac)
Harvested area secdforest \(10^6 ha\) x
q35_land_other
(j)
Other land pool calculation \(10^6 ha\) x
q35_land_secdforest
(j)
Secdforest land pool calculation \(10^6 ha\) x
q35_landdiff Difference in natveg land \(10^6 ha\) x
q35_min_forest
(j)
Minimum forest land constraint \(10^6 ha\) x
q35_min_other
(j)
Minimum other land constraint \(10^6 ha\) x
q35_other_conversion
(j)
Other land remains secondary forest \(10^6 ha\) x
q35_other_est
(j, ac)
Distribution of other land additions over ac_est \(10^6 ha\) x
q35_other_expansion
(j, ac)
Other land expansion \(10^6 ha\) x
q35_other_reduction
(j, ac)
Other land reduction \(10^6 ha\) x
q35_primforest_reduction
(j)
Primforest reduction \(10^6 ha\) x
q35_prod_other
(j)
Production of woody biomass from other land \(10^6 tDM/yr\) x
q35_prod_primforest
(j)
Production of woody biomass from primary forests \(10^6 tDM/yr\) x
q35_prod_secdforest
(j)
Production of woody biomass from secondary forests \(10^6 tDM/yr\) x
q35_secdforest_conversion
(j)
Secondary forest remains secondary forest \(10^6 ha\) x
q35_secdforest_est
(j, ac)
Distribution of secdforest additions over ac_est \(10^6 ha\) x
q35_secdforest_expansion
(j, ac)
Secdforest reduction \(10^6 ha\) x
q35_secdforest_reduction
(j, ac)
Secdforest reduction \(10^6 ha\) x
s35_forest_damage Damage simulation in forests \(0=none 1=shifting agriculture 2= Damage from shifting agriculture is faded out by c35_forest_damage_end\) x
s35_hvarea Flag for harvested area \(0=zero 1=exognous 2=endogneous\) x
s35_hvarea_other annual other land harvest rate for s35_hvarea equals 1 \(percent/year\) x
s35_hvarea_primforest annual primforest harvest rate for s35_hvarea equals 1 \(percent/year\) x
s35_hvarea_secdforest annual secdforest harvest rate for s35_hvarea equals 1 \(percent/year\) x
s35_natveg_harvest_shr Constrains the allowed wood harvest from natural vegetation (1=unconstrained) \(1\) x
s35_secdf_distribution Flag for secdf initialization (0=all secondary forest in highest age class 1=Equal distribution among all age classes 2=Poulter distribution from MODIS satellite data) \(1\) x
s35_shift number of 5-year age-classes corresponding to current time step length \(1\) x
s35_timber_harvest_cost_other Cost for harvesting from other land \(USD/ha\) x
s35_timber_harvest_cost_primforest Cost for harvesting from primary forest \(USD/ha\) x
s35_timber_harvest_cost_secdforest Cost for harvesting from secondary forest \(USD/ha\) x
v35_hvarea_other
(j, ac)
Harvested area from other land \(10^6 ha\) x
v35_hvarea_primforest
(j)
Harvested area from primary forest \(10^6 ha\) x
v35_hvarea_secdforest
(j, ac)
Harvested area from secondary forest \(10^6 ha\) x
v35_other
(j, ac)
Detailed stock of other land \(10^6 ha\) x
v35_other_expansion
(j, ac)
Other land expansion compared to previous timestep \(10^6 ha\) x
v35_other_reduction
(j, ac)
Other land reduction compared to previous timestep \(10^6 ha\) x
v35_primforest_reduction
(j)
Primforest reduction compared to previous timestep \(10^6 ha\) x
v35_secdforest
(j, ac)
Detailed stock of secdforest \(10^6 ha\) x
v35_secdforest_expansion
(j, ac)
Secdforest reduction compared to previous timestep \(10^6 ha\) x
v35_secdforest_reduction
(j, ac)
Secdforest reduction compared to previous timestep \(10^6 ha\) x

Sets

sets in use
  description
ac Age classes
ac_est(ac) Dynamic subset of age classes for establishment
ac_planted(ac) Young age classes which probably belong to managed forest
ac_sub(ac) Dynamic subset of age classes excluding establishment
ac_to_bii_class_secd(ac, bii_class_secd) Mapping between forest ageclasses and bii coefficent land cover classes
ag_pools(c_pools) Above ground carbon pools
age Population age groups
bii_class_secd(bii_class44) bii coefficent land cover classes secondary vegetation
bii_class44 bii coefficent land cover classes
c_pools Carbon pools
cell(i, j) number of LPJ cells per region i
combined_loss(driver_source) Combined loss from fire plus agriculture
ct(t) Current time period
driver_source Source of deforestation drivers
forest_land(land) land from which timber can be taken away
i all economic regions
i_to_iso(i, iso) mapping regions to iso countries
i2(i) World regions (dynamic set)
iso list of iso countries
j number of LPJ cells
j2(j) Spatial Clusters (dynamic set)
kforestry(k) forestry products
land Land pools
land_natveg(forest_land) Natural vegetation land pools
landcover44 land cover classes used in bii calculation
luh2_side_layers10 side layers from LUH2
pol_stock35 Land types for land protection policies
pol35 Land protection policy
policy_countries35(iso) countries to be affected by land protection policy
potnatveg(luh2_side_layers10) potentially forested biomes
prot_target35 Target year for nature protection
prot_type_all Conservation priority areas
prot_type(prot_type_all) Conservation priority areas
t_all(t_ext) 5-year time periods
t_ini10 Time periods with land initialization data
t_past(t_all) Timesteps with observed data
t(t_all) Simulated time periods
Target year for set aside policy
type GAMS variable attribute used for the output

Authors

Florian Humpenöder, Abhijeet Mishra

See Also

09_drivers, 10_land, 11_costs, 14_yields, 29_ageclass, 44_biodiversity, 52_carbon, 73_timber

References

Hurtt, George C, Louise P Chini, Ritvik Sahajpal, Steve E Frolking, Benjamin Bodirsky, Katherine V Calvin, Jonathan C Doelman, et al. 2018. “LUH2: Harmonization of Global Land-Use Scenarios for the Period 850-2100.” AGUFM 2018: GC13A–01.