land area needed to sequester CO2 by planting trees

I made some calculations to address two obvious and important questions regarding CO2 sequestration. 

To sequester all of the annual atmospheric increase in CO2 with a citrus forest having a 8.3* tons per hectare per year CO2 uptake[1], an area equivalent with three times that of Australia would need to be in active cultivation. Using a value of 30 tons per hectare, representative of C4 plants like corn, sorghum, sugar cane [1], one gets 0.8 x Australia. Yet, as those crop products are consumed and the byproducts decompose, the carbon finds its way back to the atmosphere.

Question: What fraction of Earth’s land area would be needed to sequester the 50 ppm CO2 surplus we currently have in our atmosphere, 50 ppm above the upper safe limit of 350 ppm? 

It’s not a fraction, per se. No. Seven times Earth’s land area would need to be in cultivation. I earlier had a more optimistic value based on 30 tons per hectare, half the Earth’s land area would need to be in cultivation. Yet, unfortunately, the associated crops are not suited for long term sequestration.

ps. The calculations are on one of the 9 benefits of the massive scale tree planting I believe we need to increase climate stability and peace globally:

  1. carbon sequestration
  2. humidification of ground and air
  3. wildlife habitat restoration
  4. food production
  5. human habitat creation
  6. employment in forestry and related industry
  7. sustainable timber production
  8. sustainable economic development modeling
  9. hope

* I had earlier taken 30 tons per hectare from an innacurate source. So I reran the calculation using 8.3 tons per hectare after [1].

[1] Carvajal M., PhD. 2010. Investigation into CO2 absorption of the most representative agricultural crops of the region of Murcia, Spain