Swanni Tatiana Alvarado

Aujourd'hui la perte et la transformation des habitats sont les principales menaces qui causent la diminution de la diversité biologique. A Madagascar, 90% des espèces végétales sont endémiques de l’île et la plupart des formations végétales sont actuellement fortement dégradées ou remplacées par des formations secondaires résultant des activités humaines. Le bois de tapia, dominé par l’espèce endémique de Madagascar Uapaca bojeri, est une formation végétale sclérophylle limitée aux Hautes Terres de l’île. Cette formation, adaptée et résistante au régime de feu naturel de la région, est aujourd'hui fragmentée, couvrant une surface équivalente à 132 255 ha au total. Afin d’augmenter la protection du bois de tapia, une nouvelle aire protégée (NAP) a été établie sur le Massif d’Ibity. L’état actuel de la végétation de bois de tapia est le résultat de l’interaction de facteurs comme le type de sol, le climat, les pratiques humaines traditionnelles et le feu. Bien que le feu soit un des phénomènes qui fasse partie de la dynamique de cette végétation, le régime de feu actuel est également une des causes de sa dégradation. L’objectif de cette thèse est donc d’étudier le rôle du feu sur le cycle démographique et certains processus importants pour l’installation et le recrutement. Ainsi, la germination, la phénologie et la résistance des plantules au feu ont été étudiées. Cette recherche montre que le problème actuel du bois de tapia est 1) la réduction de la floraison et de la fructification par les fréquences de feu élevées ; 2) la réduction du pourcentage de germination après l’exposition des graines à de hautes températures, et 3) la mortalité élevée des plantules après le passage d’un feu, en particulier quand la quantité de combustible est élevée. Ainsi l’installation et le recrutement des espèces ligneuses sont limités par le feu, qui a un effet négatif sur la régénération naturelle. La gestion du feu autour de l’aire protégée est ainsi nécessaire pour sa conservation

Páramos, high-mountain tropical ecosystems, are crucial for carbon storage and water regulation for many Andean cities. However, they are subjected to wildland fires that threaten the ecosystem services they provide. Fire activity varies substantially among páramos, making it essential to understand the drivers of this spatial variability. This study evaluates the relative influence of anthropogenic and biophysical factors on fire occurrence in Colombian páramos, analyzing burned area data from 2000 to 2022 using a Random Forest model. Results indicate that fire occurrence is shaped by the interaction between human pressures and biophysical characteristics. Annual precipitation was the most influential predictor: areas with lower mean annual precipitation (<1000–1500 mm/year) were linked to greater burned area. Vegetation cover, assessed using the Normalized Difference Vegetation Index (NDVI), showed a hump-shaped relationship, with intermediate greenness levels (0.13–0.25) being most prone to burning. Anthropogenic factors, especially proximity to buildings and agricultural zones, also had a significant impact. Our results show that fire occurrence in páramos cannot be attributed solely to human pressures but results from the combined effect of anthropogenic and biophysical drivers. Understanding of these interactions underscores the need for socio-ecological perspectives to guide integrated and adaptive management of strategic high-mountain ecosystems.

Páramos, high-mountain tropical ecosystems, are crucial for carbon storage and water regulation for many Andean cities. However, they are subjected to wildland fires that threaten the ecosystem services they provide. Fire activity varies substantially among páramos, making it essential to understand the drivers of this spatial variability. This study evaluates the relative influence of anthropogenic and biophysical factors on fire occurrence in Colombian páramos, analyzing burned area data from 2000 to 2022 using a Random Forest model. Result indicate that fire occurrence is shaped by the interaction between human pressures and biophysical characteristics. Annual precipitation was the most influential predictor: areas with lower mean annual precipitation (< 1000–1500 mm/year) were linked to greater burned area. Vegetation cover, assessed using the Nor-malized Difference Vegetation Index (NDVI), showed a hump-shaped relationship, with intermediate greenness levels (0.13–0.25) being most prone to burning. Anthropogenic factors, especially proximity to buildings and agricultural zones, also had a significant impact. Our results show that fire occurrence in páramos cannot be attributed solely to human pressures but results from the combined effect of anthropogenic and biophysical drivers. Understanding of these interactions underscores the need for socio-ecological perspectives to guide integrated and adaptive management of strategic high-mountain ecosystems.

Los rasgos funcionales son características relacionadas con las funciones de los ecosistemas, y son útiles para la selección de especies para restauración. Se evaluaron los rasgos funcionales, la propagación y el desempeño en campo de Buddleja bullata, Viburnum triphyllum y Coriaria ruscifolia, así como su potencial para la restauración del bosque altoandino. Se midieron rasgos del individuo, foliares, regenerativos y radiculares. Se colectaron semillas y se determinó el porcentaje de germinación y supervivencia, además de las tasas de crecimiento en altura y cobertura. B. bullata presentó los mayores valores de cobertura, producción de hojarasca y germinación, sugiriendo su utilidad en la formación de doseles y alta viabilidad de sus semillas. V. triphyllum es útil en la formación de doseles y la atracción de fauna, y presentó las mayores tasas de crecimiento y supervivencia. C. ruscifolia favorece la atracción de fauna y presentó simbiosis con micorrizas y bacterias fijadoras de nitrógeno.

Background and aims – Bats are the third most important animal pollinators in the Brazilian Caatinga seasonally dry forest, but little is known about the conservation status of the chiropterophilous plant species in this domain, and their main threats. The Scottian shortfall relates to deficits in assessments of IUCN conservation statuses. We aimed to evaluate the current conservation status of chiropterophilous species in the Caatinga, investigate the main changes in land use and land cover in the last years and their impacts on conservation of these species. Material and methods – We compiled a dataset and evaluated the extinction risk of 16 species following the IUCN Red List categories and criteria using the geographic range criterion. Analyses of reductions of natural vegetation were carried out using data from the project MapBiomas. Key results – Our results show that approximately 80% of the assessed species saw their conditions worsen in the last years. We verified that Dyckia viridiflora and Ipomoea vespertilia are categorized as Endangered and Stigmatodon limae is considered Vulnerable. The main sources of disturbances impacting these species according to land use are pastures and mosaics of land uses, but we highlight that urbanization is the second or third most important threat for all species. The three main threats affected the species differently. Although half of the species is assessed as Least Concern, all species had their suitable areas impacted by human activities.

Fire, a dual-edged phenomenon, holds the potential for both harm and benefit to individuals and ecosystems contingent on its location, timing, and manner of occurrence. The expansion of human civilization has positioned it as the main source of fire ignitions on the Earth, fundamentally altering natural fire regimes. Ecosystems exhibit different responses and susceptibilities to fire, with impacts varying based on specific ecosystem characteristics. Across the Brazilian landscapes, distinct biomes such as Cerrado, Pampa, and Pantanal are classified as fire-dependent. In contrast, forest-dominated biomes like the Atlantic Forest and Amazon are deemed fire-sensitive, while the Caatinga, despite limited research on its historical fire relationship, is tentatively categorized as fire-independent.Brazil has witnessed unprecedented wildfires in recent decades, with natural fire regimes undergoing modification due to human activities, frequently tied to land-use and its changes practices or exacerbated by climate extremes associated with global warming. In this context, our goal was to characterize the temporal patterns of fires in Brazilian biomes, using a burned area dataset obtained from the Global Fire Atlas (2003-2018). This dataset tracks the daily dynamics of individual fires, and our analysis focused on the burned area extent.In Brazil, over the time series (2003-2018), the peak years regarding the extent of burned areas were 2010, 2007 and 2012, totalling 392,057 km², 382,163 km², and 249,596 km², respectively. 2010 and 2007 presented an increase of ~240% above the mean, while 2012 an increase of ~150% above the mean.Regarding the intra-annual fire patterns, observations revealed that Fire-sensitive biomes, in the Amazon and Atlantic Forest, the fire season was well-defined in two months, specifically August and September, representing, on average, 55% (4,058 km²) and 40% (1,027 km²) of the total burned area, respectively. In the Fire-independent biome, Caatinga, the fire season was prominent in September and October, constituting 67% (436 km²) of the total burned area. In relation to Fire-dependent biomes, Cerrado and Pantanal exhibited a concentrated fire season in August and September, accounting for 57% (10,283 km²) in Cerrado and 68% (900 km²) in Pantanal. Finally, Pampa's fire season displayed a heterogeneous configuration over time, making it impossible to extract a specific pattern of fire season.In general, August and September of 2010 were the months that presented the greatest extent of burned area in the time series, in almost all biomes, except Pantanal and Pampa. The occurrence of fires, often caused by human actions, also can be associated with mega-droughts and ocean circulations such as the El Niño-Southern Oscillation (ENSO) event. The widespread occurrence of fires in 2010 can be attributed to the severe and unique drought that occurred as a consequence of the ENSO, affecting mainly Cerrado and Amazon.In summary, the intensification of extreme events and the increase of fire source ignitions, even in fire-dependent environments, is affecting the Brazilian ecosystems, which presents distincts behavior and resilience in relation to fire events. Therefore, understanding the period of fire season is essential to develop command-and-control approaches and to fire prevention.

Forest fires in Colombia are increasingly catastrophic. The lack of studies in the Andean region makes it difficult to understand their causes and long-term effects. This study in the department of Tolima analyzed active fires from the MODIS sensor between 2001 and 2022 and their relationship with variables such as monthly precipitation, vegetation cover, and terrain elevation. Geographic Information Systems were used and the variables in the study area were analyzed by spatial correlation and geoprocessing. A total of 7334 active fires were found, with bimodal patterns, August and September being the months with the highest number of records. Monthly precipitation showed a low correlation with the presence of active fire, and the affected areas included forests and non-forest cover below 1000 m of altitude. The results contribute to the understanding of fires at the departmental level.

Forest fires in Colombia are increasingly catastrophic. The lack of studies in the Andean region makes it difficult to understand their causes and long-term effects. This study in the department of Tolima analyzed active fires from the MODIS sensor between 2001 and 2022 and their relationship with variables such as monthly precipitation, vegetation cover, and terrain elevation. Geographic Information Systems were used and the variables in the study area were analyzed by spatial correlation and geoprocessing. A total of 7334 active fires were found, with bimodal patterns, August and September being the months with the highest number of records. Monthly precipitation showed a low correlation with the presence of active fire, and the affected areas included forests and non-forest cover below 1000 m of altitude. The results contribute to the understanding of fires at the departmental level.