Effects of dispersal- and niche-based factors on tree recruitment in tropical wet forest restoration.

Both dispersal- and niche-based factors can impose major barriers on tree establishment. Our understanding of how these factors interact to determine recruitment rates is based primarily on findings from mature tropical forests, despite the fact that a majority of tropical forests are now secondary. Consequently, factors influencing seed limitation and the seed-to-seedling transition (STS) in disturbed landscapes, and how those factors shift during succession, are not well understood. We used a 3.5-yr record of seed rain and seedling establishment to investigate factors influencing tree recruitment after a decade of recovery in a tropical wet forest restoration experiment in southern Costa Rica. We asked (1) how do a range of restoration treatments (natural regeneration, applied nucleation, plantation), canopy cover, and life-history traits influence the STS and (2) how do seed and establishment limitation (lack of seed arrival or lack of seedling recruitment, respectively) influence vegetation recovery within restoration treatments as compared to remnant forest? We did not observe any differences in STS rates across restoration treatments. However, STS rates were lowest in adjacent later successional remnant forests, where seed source availability did not highly limit seed arrival, underscoring that niche-based processes may increasingly limit recruitment as succession unfolds. Additionally, larger-seeded species had consistently higher STS rates across treatments and remnant forests, though establishment limitation for these species was lowest in the remnant forests. Species were generally seed limited and almost all were establishment limited; these patterns were consistent across treatments. However, our results suggest that differences in recruitment rates could be driven by differential dispersal to treatments with higher canopy cover. We found evidence that barriers to recruitment shift during succession, with the influence of seed limitation, mediated by species-level seed deposition rates, giving way to niche-based processes. However, establishment limitation was lowest in the remnant forests for large-seeded and late successional species, highlighting the importance of habitat specialization and life-history traits in dictating recruitment dynamics. Overall, results demonstrate that active restoration approaches such as tree planting catalyze forest recovery, not only by decreasing components of seed limitation, but also by developing canopy cover that increases establishment rates of larger-seeded species.

Analysis of food system drivers of deforestation highlights foreign direct investments and urbanization as threats to tropical forests.

Approximately 90% of global forest cover changes between 2000 and 2018 were attributable to agricultural expansion, making food production the leading direct driver of deforestation. While previous studies have focused on the interaction between human and environmental systems, limited research has explored deforestation from a food system perspective. This study analyzes the drivers of deforestation in 40 tropical and subtropical countries (2004-2021) through the lenses of consumption/demand, production/supply and trade/distribution using Extreme Gradient Boosting (XGBoost) models. Our models explained a substantial portion of deforestation variability globally (R2 = 0.74) and in Asia (R2 = 0.81) and Latin America (R2 = 0.73). The results indicate that trade- and demand-side dynamics, specifically foreign direct investments and urban population growth, play key roles in influencing deforestation trends at these scales, suggesting that food system-based interventions could be effective in mitigating deforestation. Conversely, the model for Africa showed weaker explanatory power (R2 = 0.30), suggesting that factors beyond the food system may play a larger role in this region. Our findings highlight the importance of targeting trade- and demand-side dynamics to reduce deforestation and how interventions within the food system could synergistically contribute to achieving sustainable development goals, such as climate action, life on land and zero hunger.

Has global deforestation accelerated due to the COVID-19 pandemic?

As the COVID-19 pandemic unfolded, questions arose as to whether the pandemic would amplify or pacify tropical deforestation. Early reports warned of increased deforestation rates; however, these studies were limited to a few months in 2020 or to selected regions. To better understand how the pandemic influenced tropical deforestation globally, this study used historical deforestation data (2004-2019) from the Terra-i pantropical land cover change monitoring system to project expected deforestation trends for 2020, which were used to determine whether observed deforestation deviated from expected trajectories after the first COVID-19 cases were reported. Time series analyses were conducted at the regional level for the Americas, Africa and Asia and at the country level for Brazil, Colombia, Peru, the Democratic Republic of Congo and Indonesia. Our results suggest that the pandemic did not alter the course of deforestation trends in some countries (e.g., Brazil, Indonesia), while it did in others (e.g., Peru). We posit the importance of monitoring the long-term effects of the pandemic on deforestation trends as countries prioritize economic recovery in the aftermath of the pandemic. Supplementary Information: The online version contains supplementary material available at 10.1007/s11676-022-01561-7.