|Joan's courses at Vermont Tech||
Notes from Green Hall & the cabin on the hill
A 26-year study of the 4,000-acre Harvard Forest by Melillo and colleagues from the Marine Biological Laboratory in Woods Hole has revealed that warming soils release more carbon to the atmosphere than had been hypothesized. And, this suggests that as rising levels of atmospheric carbo dioxide cause warming temperatures, warming soils may release even more carbon dioxide, triggering a positive feedback loop and driving global climate change forward. Humans may find it hard to overcome these positive feedback effects. The groundbreaking study used underground loops of cable to heat some areas 5 degrees C warmer than other areas. The top 60 cm of soil lost 17% more carbon in the warmed areas than in surrounding plots. The loses were cyclical suggesting that a the biological process involved takes time to begin, peaks and falls only to begin again. Read more about the study here.
A study of rainforests has found that the forests are so degraded that they are releasing more carbon than they store and not acting as the carbon sinks we'd hoped. Forests in South America, Africa and Asia are now releasing 425 teragrams of carbon annually, more than is produced by all traffic in the US. Interestingly, this change isn't due to deforestation. The forests are still present, but are thinner, less biodiverse and not able to take up the amounts of carbon they had in their pristine state. The causes of degradation appear to be selective logging, fire, drought and hunting. Read more in this coverage.