The United Nations Framework Convention on Climate Change is the international venue in which tropical forest carbon accounting programs and practices have been negotiated, the most visible of these being REDD + (Reduced Emissions from Deforestation and Degradation). When first imagined, the precursor of REDD + was straightforward: landowners and governments would draw revenue from a global carbon market if they could verifiably reduce their forest-sector carbon emissions to the atmosphere. The policy has at times seemed like a real possibility, but has recently faced major setbacks.

At present, more than a dozen countries are participating in preliminary work to develop REDD + implementation strategies. These efforts involve the building of infrastructure and expertise, including consulting and contracting with various academic groups and non-government organizations to estimate carbon stocks and emissions. Pledged REDD + funding now exceeds $5 billion [9]. These funds come partly from donors but primarily from governments.

Although the UNFCCC has outlined general guidelines for implementing a monitoring, reporting and verification program, most REDD + projects remain in the demonstration phase, and thus the funds are being spent in myriad ways. Because of the urgency in developing the program to meet scattershot international deadlines and twisting geopolitical expectations—current efforts to assess tropical forest carbon are highly inconsistent.

But for REDD + to function, a consistent, globally verifiable system for reporting and monitoring carbon stocks and emissions in tropical forests must be achieved in the near future. Without such an accounting system, the amount of avoided carbon emissions from deforestation and degradation achieved would not be quantifiable and thus the program would not be tractable.

The time has come for a brute-force effort to directly assess the carbon stock for all of the world’s tropical forests by 2020. Airborne LiDAR is uniquely suited for this role because it can be collected, standardized, reported and verified in a simple manner by both a landholder and any third party.

We call for a global airborne LiDAR campaign that will measure the 3-D structure of each hectare of the Earth’s non-barren land surface between the Tropic of Capricorn and Tropic of Cancer. Our targets are approximately 1,500,000,000 individual hectares of the richest and fastest disappearing habitats in the world, and the human-used lands that have replaced them.