Greenpeace, which has long opposed REDD (for ten years) held an incredible side event. You should watch the event yourself, but in essence, they rolled out a scientist and a modeler and concluded:
1) The Amazon will probably Die-back anyway from climate change, and therefore any REDD credits are not permanent.
2) REDD would swamp the market, causing a drop of 75% in the carbon price.
3) REDD would only benefit Mobil-Exxon. I swear, I'm not kidding.
On the first point, the scientist failed to note that all credible atmosphere-biosphere models show the Amazon doing just fine until 2050 and only one (the very challenged Hadley Model) showing an Amazon Die-Back. If you watch the presentation by the scientist, you would have a hard time concluding what Greenpeace did, but Greenpeace has never been one to follow facts carefully.
On the second point, many other more credible models have shown that REDD is likely to have a modest impact on prices. See EDF's report here. The modeling that Greenpeace commissioned only looked at one year in 2020, did not allow banking, and had every possible assumption to make the REDD credits look as ominous as possible.
In other bizarre twists, the workshop at one point said that Africa's REDD credits would be the largest impact on swamping the market, and then later said that it would be unlikely that Africa could actually implement REDD due to limited capacity.