Reduce the 50K DEC staking requirements for these plot types. (40? 30? 25?)
Give players that own these plot types a bonus to the amount of desalinization crystals they earn in ranked and change the white paper. Percentage of Tundra and Canyon active plots owned compared to total active plots owned times the bonus multiplier.
In the future that will give these plots a significant advantage to make up for the disadvantage they have had until now but not too much. The land 2.0 white paper says DC's can be bought with vouchers and DEC and earned in ranked and guild participation and transferable but it is not clear if they can be sold on the secondary. If you make them tradeable then that would give a revenue stream to players that own these plot types. They could choose to desalinate their region or sell some of the extra DC's.
Start thinking/working on the formula for DC's earned in ranked, it should be gated by active land ownership and a person that owns more land should earn more DC's in ranked or else it won't be possible to desalinate the regions. If 100 players with one plot each earns way more than 1 player that owns 100 plots that wont work.
I don't know what the land timeline/priority is but I would say next would be to release the rest of the common natural resource plots - wood, stone, ore and corresponding LP's however long that takes and then after that implement part of the salt system.