Four new species of Begonia are described from Northern, Peninsular and Southwestern Thailand. Three belong to Begonia sect. Diploclinium (B. exposita Phutthai & M.Hughes, B. pengchingii Phutthai & M.Hughes and B. pseudosubperfoliata Phutthai & M.Hughes), and one (B. phutthaii M.Hughes) to Begonia sect. Apterobegonia. All four species are karst limestone endemics. The provisional IUCN status of all the new species is ‘Vulnerable’.

Begonia is the world’s fastest-growing genus and a focus of intense taxonomic research. To support this, a stable and useful sectional classification is needed. This paper reviews the feasibility and challenges of creating an infrageneric classification for Begonia based on phylogenetic data, and how to overcome phylogenetic and taxonomic conflict. In particular, it (i) tests genus-wide patterns of incongruence between phylogenies based on the nuclear, chloroplast and mitochondrial genomes; (ii) explains organelle inheritance and its contribution to phylogenetic incongruence, and (iii) presents a manifesto for a workable and stable subgeneric classification in light of the above and lays the foundation for a collaborative Begonia Phylogeny Group.

Urban forests are crucial for biodiversity and climate resilience. This study investigated the impact of human disturbances on carbon (C) stocks in un-conserved forests of Entoto Mountain, Addis Ababa, Ethiopia, focusing on forest structure: important value index (IVI), species diversity (H’), regeneration pattern status, and C storage in aboveground biomass (AGB), belowground biomass (BGB), litter biomass (LB), and soil. Field data were collected from 35 quadrats across two altitudes, and human disturbances were observed, including firewood collection, tree cutting, soil excavation, and road and infrastructure inside the sample plot. Results indicate low species diversity dominated by Eucalyptus globulus Labill and Juniperus procera Hoechst. Ex Endl., with fair regeneration. Higher altitudes showed greater measured C stock (572.62 tC ha⁻¹) than lower altitudes (495.03 tC ha⁻¹), attributed to larger trees. C values in the upper altitude for AGB, BGB, LB, and soil (0–30 cm) were higher than at lower altitudes. The IVI showed a significant positive correlation with C in aboveground biomass, C in belowground biomass, and total C stock, whereas H’ also showed a significant (p < 0.05) positive correlation with the total number of trees. It is concluded that forest structures contribute to the C stock of this area. Given the importance of the un-conserved Entoto Mountain forest, it is recommended to prioritize the conservation of old-growth forest species in the area, as they demonstrate the highest capacity for C accumulation.

Plant species with small habitat ranges and specific edaphic requirements are highly vulnerable to extinction and thus require enhanced attention in biodiversity conservation. This study was designed to explore the challenges of protecting such plant species by evaluating the in situ and ex situ conservation capacities available for Thailand's species of the mega‐diverse plant genus Begonia L. A comprehensive assessment of occurrence records across the country was conducted to evaluate the spatial distribution of Begonia diversity in Thailand, identify biodiversity hotspots, assess the extinction threats faced by the 60 Begonia species known in the country, and identify existing conservation capacities and potential gaps. The results show that 78% of Begonia species in Thailand are vulnerable to extinction, with the Northern floristic region identified as both a Begonia species hotspot and a region with major conservation gaps. While in situ conservation efforts have been successful in covering over 88% of the species, they have failed to provide the protection required to achieve zero extinction. Ex situ conservation capacities are poorly developed, with only 13% of species present in botanical gardens, and no seed banking or other related activities have been initiated. This evaluation presents a sharply contrasting message: on one hand, Thailand has assembled substantial capacities to protect these plants through established national parks and other protected areas, but on the other hand, essential capacities are still lacking to render the zero extinction target achievable. We advocate for the implementation of a multi‐component conservation strategy to enable Thailand to move towards zero species extinction, even for plant species with narrow habitat ranges and high edaphic specialisation.

The Mae Chang watershed is part of the headwaters of the Wang River, located in Lampang Province in Northern Thailand. Resource pressures at forest-agriculture-extractive frontiers make this landscape crucial for studying land-habitat conversion and guiding sustainable land-use planning. Thus, this study interpreted LULC (1989, 2005, 2013, 2021) and projected LULC for 2029 and 2037 under BAU, conservation (CON), and development (DEV) scenarios using TerrSet’s LCM-MLP with local drivers, isolating intervention effects by contrasting CON/DEV (with constraint and incentive (CI) layers) against BAU (no CI). From 1989 to 2021, deciduous forest declined 23.3% (-249.01 km²), from 1,070.41 to 821.40 km² (65.40→50.18% of the watershed; -15.2 percentage points), while field crops increased by 104.7%, perennial crops by 97.3%, mines/pits by 240.8%, and urban areas by 28.8% based on human activity. Sub-model accuracies ranged 53-92%, and validation achieved Kstandard 0.824, Kno 0.861, Klocation 0.893, exceeding the success threshold. The three future scenarios yielded similar projected areas in both 2029 and 2037 but there were location differences. The deciduous forest area in 2029 and 2037 declined by 22.3% and 31.5%, respectively for all scenarios compared with 2021. The CON scenario outperformed BAU/DEV because strict no-conversion constraints in protected forests and restricted area effectively prevent ongoing deforestation, offering a practical simulation-based tool to support and implement land-use policies at local and regional scales. These findings provide a validated, transferable framework that isolates policy effects and supports evidence-based land-use planning in tropical headwatersheds.