About 71 % of the Earth's surface is covered with water, and the remaining lands are composed of 71 % of what we call habitable lands (i.e. usable for human activities), 10 % glacier and 19 % barren land.
The land use model focuses on habitable lands, which are shared between different activities:
- Land usage for food from crop and livestock
- Energy linked technologies land
The initial land distribution for habitable lands (50% for agriculture and 37% for forest in 2019), may vary with deforestation and reforestation.
The model's inputs are therefore:
- Food land surface coming from agriculture discipline
- Energy linked technologies and reforestation surface (for CCS purpose) coming from the energy mix discipline
- Deforestation surface coming from forest discipline
For each year, the available forest and agricultural surface is computed with deforestation and reforestation inputs, and a constraint is calculated for each such as:
So that the optimizer will try to minimize the absolute value of the constraint to solve the optimization problem.
Model's data
The following data (taken from 'Our World in Data'[^1]) are integrated into the model (for the 2019 year):
|Category|Name|Surface|Magnitude|Unit| | ------ | -- |:-----:|:-------:|:--:| |Earth|Land|149|M|km2| |Earth|Ocean|361|M|km2| |Land|Habitable|104|M|km2| |Land|Glacier|15|M|km2| |Land|Barren|28|M|km2| |Habitable|Agriculture|51|M|km2| |Habitable|Forest|39|M|km2| |Habitable|Shrub|12|M|km2| |Habitable|Urban|1.5|M|km2| |Habitable|Water|1.5|M|km2| |Agriculture|Livestock|40|M|km2| |Agriculture|Crops|11|M|km2|
References
[^1]: Hannah Ritchie and Max Roser (2013) - "Land Use". Published online at OurWorldInData.org. Retrieved from: 'https://ourworldindata.org/land-use'