Background
When a tree dies naturally, the wood in the stem and roots rot, and the carbon in the wood is gradually released back into the atmosphere as CO2, a natural process. When a tree is cut for lumber, the parts that are left in the forest also rot and release CO2. The log that is harvested is sawn, and the boards are made into products that have different life spans before they, too, are discarded and eventually rot. For example, CO2 sequestered in wood used to construct a house in New England may be stored for 200 years, while a wooden toy may be tossed out and rot in just a few.
Managed Forests
In the case of managed forests, on the other hand, the situation is different. If we start with a clean pasture, the tree seedlings we plant gradually grow into a closed, dense forest and accumulate CO2 in the form of wood through photosynthesis. Eventually, that forest can be partially harvested or thinned for logs while maintaining the carbon sequestration capability of the forest. If managed correctly, the forest will continue to grow and replace the extracted wood and stored CO2. Thus, a stand of trees or forest can store CO2 indefinitely, provided the forest is never clear-cut and returned to pasture. A natural tropical forest may store 200 to 400 metric tonnes of CO2 per acre in the stand.
The RTT Model
RTT reforests tropical pastures with tree species that grow quickly, form straight trees, and produce valuable lumber. RTT’s managed forests are designed to be profitable for farmers and highly effective at sequestering CO2 emissions.
In the RTT model, forests are funded by US emitters to sequester their CO2 emissions and are managed under long-term contracts with RTT. These profitable forests will earn income for the farmer even while building up stocks of CO2 stored in the forest stand for the account of the US sponsor. Research plots of selected tree species 50 years old, managed by RTT, have accumulated up to 800 tons of CO2 per acre. Our methodology for calculating the carbon content of reforested pastures is outlined here.
The RTT model strives for “permanent” carbon storage by creating a financial incentive for farmers to maintain and profit from their sustainable forests. Details about this aspect of the RTT model are here. A description and photos of a periodic thinning of a carbon-forest forest managed by RTT are here and here.
An ongoing focus of RTT’s research efforts involve maximizing the long-term carbon sequestration in our carbon-offset forests by using innovative forestry designs. RTT uses a “layer-cake design” for certain of its forests, an example of which is described here. In late 2008, Mr. Michael Ferrucci, an independent forestry consultant with InterForest LLC, reviewed and evaluated the RTT model. His summary report is available here. In the report, Mr. Ferrucci commented on RTT’s layer-cake forestry designs as follows:
It is clearly possible to create stratified mixtures of planted trees (also called a layer-cake forest) which combine fast growth, potential income, strong long-term carbon storage, and ancillary environmental benefits.
RTT’s selection of tree species is based on more than 50 years of species trials. With the layer-cake model of carbon-offset forests, others may yet prove more effective. Combinations of tree species as shown in the 30+ mixtures presently being tested are likely to be even more productive than monocultures. The optimal spacing and thinning regimes have yet to be determined, particularly for these mixed plantings.
Some of the trees RTT uses, the product of its research, namely Chancho and Deglupta, can produce commercial size logs within 6-8 years of age. This offers farmers the potential to grow and harvest trees as a commercial crop with a much shorter time for receiving income. It also increases the profitability of the crop and the chances of the forest being sustainable with long-term carbon storage.
For those interested in learning more about the methodology and performance of RTT’s experimental carbon-offset forests, we have posted a series of detailed reports, silvicultural analyses, and case studies at the following web page. For example, we’ve done a silvicultural analysis of a nine-year-old mixture of Almendro and Klinki trees in the Connecticut College Carbon-Offset Forest in Costa Rica. A silvicultural analysis of a six-year-old RTT carbon-offset forest in the Las Delicias farm is available. A case study of a six-year-old carbon-offset forest sponsored by Dr. Eric Wolf in Groton, Connecticut, is also available. A case study of a 5.7-year-old carbon-offset forest sponsored by the Home Depot Foundation is also available.
Production of Valuable Wood
An important aspect of the sustainability of RTT’s forests is their ability to generate wealth for the farmers on whose pastures the forests are planted. The wealth-generation feature creates an incentive for farmers to maintain the integrity and carbon-sequenstration ability of the forests. The importance of a model that incentivizes permanent carbon storage is describe futher here. To this end, the RTT model seeks to incorporate valuable wood in its forests.
One of the species of trees in our forests is the Mahogany tree. Mahogany produces very valuable wood, but one major drawback to this species is an insect pest, the shootborer, that incessantly attacks the young tree.
Until recently, it has been nearly impossible to plant this species because of this insect. However, RTT Forester Ing. Rolando Camacho, who manages our forests in Costa Rica, recently discovered a way to combat this insect inexpensively.
Initial results have been excellent. Without shootborer attack, Mahogany grows very quickly, as can be seen in this photo of a 1-year old forest planted and managed by RTT.
The other tree shown in the photo is the Klinkii tree, included for its excellent capacity to store CO2 for many decades in the forest stand. This forest will be managed sustainably for long-term carbon sequestration and farmer income by RTT.
Benefiting from the sequestration in this forest is the Superior Nut Company of Cambridge, Massachusetts, which sponsored this forest. Photo taken on Sept. 19, 2006 on the Tournon Farm in Costa Rica
Food Production for Workers
Another goal in designing RTT forests is the production of food for workers. During working hours, workers manage the young plantings, weeding and caring for the young forest trees until they can fend for themselves. After normal hours, they are allowed to plant and harvest crops between the rows of trees. The crops include corn, yucca, cilantro, pineapple, plantains, bananas and papaya. Some of the latter two plants are left to grow purposely to feed wildlife.
Lester Brown of the Earth Policy Institute has pointed out that “the biggest threat to global political stability is the potential for food crises in poor countries to cause governments to collapse. Those crises are brought on by rising demand and ever worsening environmental degradation.” The RTT Model forests help meet the challenges of climate change and local food scarcity in a small way.