Natural Regeneration Shifts into Reverse Gear in Latin America and the Caribbean
Schwartz, N. B., T. M. Aide, J. Graesser, H. R. Grau, and M. Uriarte. 2020. Reversals of reforestation across Latin America limit climate mitigation potential of tropical forests. Frontiers in Forests and Global Change 3:85.
Reforestation and natural regeneration in tropical landscapes have emerged as favored “natural climate solutions.” Tropical forests regenerate quickly and store large volumes of carbon, and could make a major contribution to our efforts to fight climate change. And, since tropical second-growth forests can support biodiversity conservation and human livelihoods, this solution is often seen as a win-win for carbon and other ecosystem services, making tropical reforestation particularly popular.
However, these benefits accrue over the long term. Older forests store more carbon and harbor higher levels of biodiversity. If forests are cleared again, these gains are undone. And, the risk of re-clearing may be high: regional case studies have shown that few second-growth forests persist until the old ages required to maximize carbon and other benefits.
We set out to assess whether these regional trends represented a more general pattern across tropical forest landscapes in Latin America and the Caribbean. We used a 14-year time series of land cover data derived from satellite imagery to determine where regional trends showed increasing forest cover and where increasing forest cover had subsequently declined, indicating a lack of permanence of second-growth forest.
Our study shows that unfortunately, reforestation trends frequently reversed in tropical forests across Latin America and the Caribbean between 2001 and 2014. Increases in forest cover were about ten times more likely to be at least partially re-cleared than they were to be sustained over the study period.
Clearing of second-growth forests can have large consequences for carbon sequestration. Based on our data, we estimated that had reversals of reforestation been avoided, second-growth forests could have removed over four times more carbon from the atmosphere than was actually taken up. Re-clearing of tropical second-growth forests is thus severely limiting their contribution to climate change mitigation.
Without policy changes, management actions, and monitoring, widespread permanence of second-growth forests seems unlikely in the future. A long-term perspective in restoration planning is necessary to ensure that second-growth forests are able to persist to an age where carbon, biodiversity, and other benefits are maximized, a long-term perspective in restoration planning is necessary. Better understanding the social and ecological contexts that promote permanence will also help improve permanence of second-growth forests and enhance their contribution to carbon and other ecosystem services.