Biodiversity conservation is a key factor in meeting sustainable development goals. This is even more important in cities, where green spaces are becoming increasingly scarce. This study analyzes Kinshasa’s proliferating ornamental plant nurseries, known as informal horticultural sites (IHSs). The analysis focused on characterizing the profile of horticulturists, their production conditions, and the ornamental species produced. A total of 15 IHSs were sampled using the “snowball” technique, and 178 horticulturists were surveyed. Based on the socio-professional profile of the horticulturists, five groups of IHS are distinguished after a hierarchical clustering of principal components (HCPC). We found that IHSs exclusively employed men, most of whom were new to the trade, from all levels of education, and most of whom ranged from 19 to 45 years old. Production conditions are relatively similar from one site to another. However, all IHSs are characterized by permanent land insecurity, the use of phytosanitary products, plant-conditioning methods that are not very diversified and calibrated to growers’ investment capacities, and diversified seed acquisition methods. A total of 139 ornamental species, most of them exotic, were identified. Of these, 37% are phanerophytes, and 24% are considered potentially invasive. We suggest ways of professionalizing the activity and protecting the urban environment.

This study examines the evolution of anthropogenic pressures on the Itombwe Nature Reserve and its periphery over the period 1990–2024 using satellite imagery. Two landscape ecology indices were employed: the Percentage of Landscape (PLAND) and the Largest Patch Index (LPI). The PLAND quantifies the overall extent of each habitat type, while the LPI provides insights into their spatial configuration. Eighty-three plots (each 2.5 km per side, i.e., 6.25 km²) were sampled in both the reserve and its periphery to generate robust landscape replications. Analysis focused on three key land use classes: forests, savannahs, and fields. Statistical comparisons using Kruskal–Wallis and Mann-Whitney U tests revealed a decline in forest cover within the reserve and its periphery, accompanied by a steady increase in savannahs and fields. The decline in forest cover is particularly pronounced along the reserve’s periphery. For instance, in the reserve, forest cover decreased from 78.4% in 1990 to approximately 60.2% in 2024, whereas on the periphery, it dropped from 37.5% to about 21.4%. In contrast, the savannah areas increased from 17.7% to 29.5% within the reserve and maintained a marked predominance on the periphery (rising from 53.9% to 55.2%). Additionally, the area dedicated to fields exhibited notable expansion, rising from 3.70% to 10.22% in the reserve and from 7.54% to 21.98% along the periphery. These findings underscore the significant impacts of anthropogenic pressure on the forest ecosystems in both the reserve and its periphery. They highlight the urgent need for enhanced conservation measures within the reserve, as well as the implementation of sustainable land use practices (e.g., agroforestry and sustainable agriculture) in the peripheral zones to reduce the local population’s dependence on forest resources.

Forest canopy gaps are key indicators of forest dynamics, yet their vertical organization remains poorly quantified across forest types. While canopy gaps are commonly interpreted as signatures of disturbance regimes, their size distribution and vertical organization may also reflect intrinsic differences in stand structure, crown architecture, and density-dependent interactions. We hypothesize that the vertical distribution of canopy gap size differs among forest types, reflecting contrasting structural organization and developmental trajectories. Using airborne LiDAR, we quantified vertical gap size distributions in two Central African old-growth forest types: monodominant Gilbertiodendron dewevrei (GIL) and MIXED forests, across two sites in the Democratic Republic of the Congo (Lileko and Yangambi). We also derived structural ratios normalizing gap area by basal area and canopy height. Results show clear divergence in vertical gap profiles. GIL forests consistently exhibit lower canopy openness than MIXED forests. Between heights of 10 and 20 m, total gap area per hectare ranged from 39.11 (95% CI: 19.84–83.5) to 567.56 (95% CI: 229.44–707.48) m² ha⁻¹ in GIL forests, compared with 69.10 (95% CI: 55.28–123.51) to 1244.97 (95% CI: 784.73–1360.45) m² ha⁻¹ in MIXED forests across both sites. Structural ratios further confirm that GIL forests maintain smaller gap areas relative to basal area and canopy height. Overall, the results support the three study hypotheses, demonstrating that vertical gap size distributions and their normalization by stand structural attributes provide robust and transferable indicators for discriminating among Central African old-growth forest types and developmental stages, highlighting the importance of structural context for interpreting tropical forest dynamics.