Demand data for base year taken from FAO.
Demand projected using population and GDP.

Max. wood from natural areas harvested at replacement rate.
Effect of previous land cover on wood yield only lasts for one timestep.
No wood harvest from agricultural expansion.
Added variable tree logging cost (fixes oscillating export issue).
Timber and carbon production now serialized during calibration.

Added NATURAL_REGROWTH_TIME parameter.

Further forest work on GAMS code.