How Much Carbon Are Trees Actually Sucking Up?
23rd March 2013

How Much Carbon Are Trees Actually Sucking Up?

Food for thought
Land Use
Carbon Modeling
Laser Scanning

Without a strategy to maintain the world’s forests, we may as well give up on climate change and accept our fate. Trees are that important. Deforestation contributes about 15% of all greenhouse gases, because a lot of a tree’s mass is carbon. When you cut it down or burn it, you’re effectively releasing CO2 into the atmosphere. We need trees as carbon “sinks”—they’re the best storage devices we have.

How Much Carbon Are Our Trees Actually Sucking Up?

For the last several years, Greg Asner has been mapping some of the most important forests in the world, not only measuring how many trees are left but also their capacity as climate remediation machines. He flies above the canopy in the Carnegie Airborne Observatory (CAO), a souped up twin-engine plane. On-board are two pieces of equipment: a LIDAR machine and a spectrometer. The LIDAR (Light Detection and Ranging) bounces laser signals off the trees at a rate of about 500,000 pulses per second, mapping in 3-D detail. The spectrometer measures for 21 chemical traits and gives a sense of the carbon stock and tree species diversity.

The key insight from Asner’s work is that not all forests are equal. Temperature, precipitation, soil, geology and terrain affect a tree’s ability to sequester carbon. The CAO is able to show which areas of forest are most important from a climate point of view and where we might have the most impact by replanting.

“Not only does it highlight the incredibly important global role of tropical forests in storing carbon, it shows precisely where the most carbon is stored within tropical forest regions,” Asner says, via email. “This is allowing for most tactical or targeted conservation of those high-carbon forests.”

The research has also revealed that what we thought we knew about carbon sinks was wrong. Both satellites and on-the-ground surveys failed to show the natural difference in carbon storage, nor the extent of human impact through mining, logging, agriculture and housing.

Asner, who is based at the Carnegie Institution for Science, spends up to six months of the year in the air. So far he and his team have mapped forests in the Andes and western Amazon, including Peru, Ecuador and Colombia, as well forests in South Africa and Madagascar, and in Hawaii. The research quantifies the impact of a country’s development plans and can be used in international climate negotiations to assess how a country should be compensated for not developing. Such compensation schemes are key to potential future agreements.

“Without the detailed maps that we make, it is unlikely that protections will be put in the most efficient or impactful portions of our planet, in terms of sequestering carbon and slowing climate change,” Asner says.