Removing climbers more than doubles tree growth and biomass in degraded tropical forests

Huge areas of tropical forests are degraded, reducing their biodiversity, carbon, and timber value. The recovery of these degraded forests can be significantly inhibited by climbing plants such as lianas. Removal of super-abundant climbers thus represents a restoration action with huge potential for application across the tropics. While experimental studies largely report positive impacts of climber removal on tree growth and biomass accumulation, the efficacy of climber removal varies widely, with high uncertainty as to where and how to apply the technique. Using meta-analytic techniques, we synthesize results from 26 studies to quantify the efficacy of climber removal for promoting tree growth and biomass accumulation. We find that climber removal increases tree growth by 156% and biomass accumulation by 209% compared to untreated forest, and that efficacy remains for at least 19 years. Extrapolating from these results, climber removal could sequester an additional 32 Gigatons of CO2 over 10 years, at low cost, across regrowth, and production forests. Our analysis also revealed that climber removal studies are concentrated in the Neotropics (N = 22), relative to Africa (N = 2) and Asia (N = 2), preventing our study from assessing the influence of region on removal efficacy. While we found some evidence that enhancement of tree growth and AGB accumulation varies across disturbance context and removal method, but not across climate, the number and geographical distribution of studies limits the strength of these conclusions. Climber removal could contribute significantly to reducing global carbon emissions and enhancing the timber and biomass stocks of degraded forests, ultimately protecting them from conversion. However, we urgently need to assess the efficacy of removal outside the Neotropics, and consider the potential negative consequences of climber removal under drought conditions and for biodiversity

Doing burden-sharing right to deliver natural climate solutions for carbon dioxide removal

Carbon dioxide removal (CDR) figures prominently in modelled pathways to achieve the Paris Agreement's goal of limiting global warming to 1.5-2°C compared to pre-industrial levels. However, national roles and responsibilities to deliver CDR have been informed with CDR quota analyses that focus on developed economies and global major emitters. This study extends the discussion to implications for developing countries. For that purpose, we employ a diverse set of allocation methods on a wide range of global emissions scenarios to address equitability and uncertainty in sharing the burden of climate change mitigation. We further focus on tropical developing countries due to their large potential for natural climate solutions (NCS) that deliver CDR. Our analysis indicates the potential for stringent CDR quotas for the top seven countries that contribute ∼60% of pantropical cost-effective NCS potential, with median national quotas across emissions scenarios ranging from 0.1-29 GtCO2. However, the results reveal strong heterogeneity of quotas and inherent bias across allocation methods making agreement on an ‘equitable’ quota unlikely. Competition among NCS and non-NCS CDR options may arise when ambitious CDR quotas are implemented in countries with vast forest areas or large potential for expansion of tree cover. Therefore, it is important to not use CDR quotas to evaluate national climate actions or to inform climate targets that could exacerbate trade-offs between emissions reduction, biodiversity and ecosystem services in these NCS-rich countries. Instead, results from burden-sharing exercises could foster higher ambition if used to inform voluntary cooperation mechanisms. Discrepancy between perceived fairness and CDR quotas should be critically and transparently embraced to encourage acknowledgment of socio-ecological co-benefits as compensation. Such an approach will allow tropical developing economies to prioritise protection and restoration of nature in their climate change mitigation pathways

Regeneração de espécies arbóreas sob a influência de Merostachys multiramea Hack. (Poaceae) em uma floresta subtropical Regeneration of tree species influenced by Merostachys multiramea Hack. (Poaceae) in a subtropical forest

A ocorrência de bambúseas é comum em muitas fisionomias florestais, sendo que a elevada abundância destas espécies pode interagir com a regeneração de espécies arbóreas. Foi avaliada a regeneração de espécies arbóreas e de Merostachys multiramea Hack. em uma área de transição entre Floresta Ombrófila Mista e Floresta Estacional no Sul do Brasil e comparada a estrutura de regeneração da área entre dois e quatro anos após floração, frutificação e morte de M. multiramea. Foram alocadas 25 unidades amostrais de 100 m² dispostas de forma aleatória, onde foram amostrados todos os colmos vivos de M. multiramea e indivíduos regenerantes de espécies arbóreas > 30 cm de altura e com perímetro à altura do peito < 15 cm. Foram amostrados 4.372 indivíduos vivos de bambu e 2.918 indivíduos regenerantes, pertencentes a 32 famílias e 75 espécies. A maioria das espécies é zoocórica, dependentes de luz para germinação e formadoras de dossel, porém, a abundância de indivíduos revelou maior contribuição de indivíduos autocóricos, tolerantes à sombra e de sub-bosque. A densidade de M. multiramea elevou-se ao longo dos quatro anos após período reprodutivo (p< 0,05), com aumento da altura média dos colmos (p<0,01), mas sem alteração no número médio de colmos (p=0,46). Uma NPMANOVA revelou diferenças significativas entre composição e respectivas abundâncias entre os levantamentos, com maior similaridade entre as amostras de dois anos após o período reprodutivo de M. multiramea. Houve aumento da riqueza específica ao longo do tempo, estando diretamente associada à abundância de M. multiramea (p=0,002), porém, com diminuição da uniformidade de abundâncias entre espécies em regeneração.<br>The occurrence of bamboo species is common in several forest physiognomies, and the high abundance of these species may affect the regeneration of other ones. We evaluated both tree species and Merostachys multiramea Hack. recruitment in a transition area between mixed Araucaria rain forest and seasonal semideciduous forests in southern Brazil. We compared the regeneration structure of the areas evaluated two and four years after flowering, fruiting and death of M. multiramea. We randomly distributed 25 100 m² sampling units, and surveyed all living culms of M. multiramea and tree saplings. We sampled 4,372 living bamboos and 2,918 tree saplings, belonging to 32 plant families and 75 species. Most species were classified as zoochorous and canopy light-demanding. On the other hand, plant abundance revealed a greater contribution of autochorous, understory and shade-tolerant trees. M. multiramea density was higher over the four years after the reproductive event (p<0.05), with taller culms (p<0.01), but with the same mean number of culms (p=0.46). A NPMANOVA revealed significant differences in composition and abundance between surveys, with higher similarity among samplings two years after the reproductive event of M. multiramea. We also detected higher species richness over the study period, which was found to be directly associated with the abundance of M. multiramea (p=0.002), but with lower evenness of abundance among regenerating species