Tropical Forests: No Longer A Carbon Sink

Trees and plants are known for their ability to draw carbon dioxide out of the atmosphere, and up until recently, the net-global forest sink was estimated to be around 1.1 Petagrams (1015 g) of Carbon annually from 1990 – 2007. This has to take into account the additional carbon emitted due to land-use change and deforestation, however a new study determined that tropical forests are actually a significantly large carbon source rather than a carbon sink. This not only poses a problem for future atmospheric CO2 predications, but also disrupts current plans for curbing greenhouse gas emissions set by the Paris Climate agreement.

Putting aside whether or not countries will stick to these emission agreements, most nations expected the land sector to mitigate up to a quarter of their total pledged reductions by 2030. This drastic change in data now presents the issue of how to compensate for the extra carbon which countries initially expected to be absorbed naturally by vegetation. Dr. Alessandro Baccini states that the unexpected rise in human activity within forested areas has increased deforestation at a much faster rate than was predicated and is one of the leading factors for the substantially greater levels of carbon emission. Ultimately land degradation and disturbances accounts for 69% of the total carbon lost from tropical forests.

CarbonDensityChangesChanges in carbon density from 2003 – 2014. Source: Baccini et al (2017)

With such a drastic change in the overall outlook on the world’s net carbon exchange, “negative emission techniques” are being analyzed in greater detail in attempt to shift tropical forests back towards being a carbon sink. Two of the most common methods currently being used to replenish the carbon density within tropical forests are reforesting areas which have experienced heavy degradation as well as expanding current foliage areas (afforestation). Both of these methods aim the increase the rate of carbon withdrawn from the atmosphere and the total capacity for carbon the forests can retain. Estimates for these techniques suggest an average removal of 3.7 tons of CO2 per hectare of forest per year with an associated cost of $20-100 per ton.

Additionally, a relatively modern carbon-capture technique uses “Biochar” to offset CO2 emissions. Biochar is essentially a charcoal made from burning biomass while the supply of oxygen is cut off. This process named pyrolysis prevents the carbon accumulated in the matter before burning from breaking down at a normal rate. The resulting biochar is added to soils which helps distribute nutrients and water all while limiting carbon release into the atmosphere. This is a fairly primitive carbon storage technique, but its estimated that up to 4.8 billion tons of CO2 can be sequestered using biochar each year.

These are only a few examples of carbon reducing strategies, but seeing as the carbon is building up in the atmosphere at even quicker rates than have been predicted, more creative and drastic steps need to be taken to handle the issue in time. In terms of efficiently reducing/storing carbon and cost effectiveness, what other strategies could be pursued to help offset the carbon flux? Also, what implications could this have on future environmental policy including international agreements?


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10 thoughts on “Tropical Forests: No Longer A Carbon Sink

  1. This post seems to be rather relevant in our class as of right now. I am very curious as to how long and tedious the process of reforestation is and how long it will take to see the effects of such a solution. It is very interesting how something that has been practiced for hundreds of years can have a potential to reduce emissions of carbon while also retaining nutrients and water in the soil. Ideally, agreements in the future will be more like international mandates in order to reduce carbon as it is clearly a rapidly growing global issue.


  2. I have never heard of the Biochar technique for carbon sequestration. Are they just taking the dead biomass and rather than let the carbon be emitted through decomposition, they turn it into charcoal to capture the carbon and return it to the ground? That’s a really interesting technique but I worry it is a very energy intensive technique as well. Reforesting areas might be the easier and more healthy method. It’s definitely easy to see the huge amount of environmental damage deforesting commits in that map you have shown.


  3. I have never heard of Biochar as others have mentioned as a way to sequester carbon. My question is what happens to the Biochar after 10-30 years? Does it break down and just prolong the carbon emission? I don’t think we will ever find a great way to sequester carbon and store it somewhere where its not going to leak or eventually degrade and release all of the stored carbon. I think the better route would be to replant trees to try to get the rain forests back to being a carbon sink and let the Earth get rid of the carbon naturally while we are trying to reduce the carbon emitted.


  4. In combination of fossil fuels and removing forests, we seem to be putting as much carbon as we can back into the atmosphere which doesn’t seem to be a great thing. I feel environmental pressures will hopefully lead to government incentives into increased carbon capture research. I don’t believe swapping over to cleaner energy will be a quick enough transition to reverse the damage done and future damage. I believe technological advances will be key into creating new carbon sinks.


  5. Humans seemed to have dumped large amounts of greenhouse gases into the ozone depleting its strength while also destroying the natural CO2 vacuums that trees and other greenery provide. This stupidity has lead us to extremely levels of CO2 and other greenhouse gases in the ozone. We need to combat this by replenishing the natural vacuums that we have been destroying for years. Additionally we need to limit our CO2 emissions which needs to be enforced by the government. If we can decrease our pollution rates we will have a much better chance at fighting this.


  6. This post was an interesting read but a sobering one at the same time. It seems like every time humanity seems to be making strides towards tackling climate change and coming up with solutions, another problem appears that must be addressed. While this is the nature of the world, it is hard not to be hopeless when thinking about the future of our climate on this planet. It is encouraging to see new solutions being innovated and put into practice such as the Biochar method, but much more than this needs to happen in order for us to slow down the effects of climate change.


  7. The biochar seems like a great idea. I know scientists have explored using many options to actually removing carbon out of the atmosphere. The only pitfall to this is that if we find an effective way to remove CO2 out of the atmosphere, then people and industries will begin to longer care as much about reducing emissions. This will lead us back into heavily relying on fossil fuels and it might lead us to abandon progress made in finding alternative energy sources. Great article and thanks for sharing.


  8. With deforestation rates being as high as they are, carbon capture technology is a crucial need. The deforestation is not going to stop, and neither is the release of enormous amounts of CO2, so something has to be done. Biochar is a good step in carbon capture technology, but like you said, is still sort of primitive. You would think it would only be a matter of time before a new, more effective method is discovered, but who knows how long that might take?


  9. It is interesting that so many nations like Indonesia and especially Brazil have made it a point to reduce their carbon emissions by reforestation. The eyes on the ground would prove otherwise with corruption and powerful corporate entities fueling the deforestation problem in both nations. Deforestation is a huge contributor to greenhouse gases ontop of destroying future carbon sinks. You have a two for one punch: Burning Carbon and Eliminating a Future Storage Area for Atmospheric Carbon. There are some good trends in the world. Developed nations like the US, Europe and nondeveloped ones like Africa (with huge reforestation projects) actually increased carbon sinks through reforestation. However, the good does not outweigh the bad currently…


  10. Well this is not good news. I understand that this has probably been a gradual trend for while and that rainforests did not suddenly shift from being a carbon sink to a carbon source due to deforestation overnight. But still. It is a profound statistic that we have managed to throw a major ecosystem so out of balance that it is no longer performing one if its basic ecosystem services. Biochar seems like an interesting option for carbon storage – is it useful as some other product? For cooking or fertilizer or anything in that regard?


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