From sink to source?

In 3 years, how did the world's rainforests go from carbon sink to carbon source? I know it isn't a credible scientific study to measure climate problems by newspaper headlines - but these Guardian headlines (2014 and 2017) are completely contradictory, and they were published only three years apart. The articles, based on two scientific papers (Asner et al., 2014 and Baccini et al., 2017), are essentially suggesting that the world's rainforests have gone from being heralded as storing more CO2 than the US emits in a year, to being lambasted for releasing MORE carbon than all of the US traffic does in a year - is it true? Have our rainforests turned from carbon stores to carbon sources?

Unsurprisingly, it is not a straightforward matter. From reading the papers it becomes clear that the authors each have different measures for carbon sequestration. The results from each study have been analysed/manipulated carefully in order to prove/disprove the carbon storage abilities of rainforests. An important point to note is that Baccini et al do not consider non-woody or herbaceous species, nor do they take into account soil carbon storage properties, they are strictly focusing on trees in rainforests. Asner et al however, use completely different measures for carbon storage, their approach of 'high-resolution carbon mapping' helped them target carbon stocks in Peru that are vulnerable to degradation. From delving into these papers a little further, it is clear that due to their contrasting methodologies, they aren't directly comparable - however - it appears that the authors from the Guardian articles have interpreted the results in similar ways in order to create shocking headlines, enticing the eco-aware-Sunday-browsing reader (me). Regardless of their direct comparability, what is obvious from the two papers and related literature in the field (Fisher et al, 2013 & Alamgir et al., 2016), is that it is not clear what the exact state of the world's rainforests are in when it comes to carbon sequestration.

Logging activities in Indonesian rainforest, 2010. 

What both papers do provide, is evidence for the fact that land degradation activities and deforestation pose huge risks to the potential longevity of rainforests as carbon sinks. The role of rainforests as carbon sinks/regulating GHG emissions is just one of the ecosystem services that rainforests provide. Harking back to my first blog post, the potential symbiosis between humans and the rainforest is threatened by the ongoing degeneration they are experiencing. As rainforests continue to be ravaged by land use change, clearing and logging (all human activities), ecosystem services that humans rely on will be damaged. The articles discussed in this post bring an important topic to their readers attention: if we want biodiversity, if we want to limit the effects of climate change - we've got to start protecting our rainforests!