Fires dynamics in the Pantanal: Impacts of anthropogenic activities and climate change

The role of microbial communities in biogeochemical cycles and greenhouse gas emissions within tropical soda lakes

Although anthropogenic activities are the primary drivers of increased greenhouse gas (GHG) emissions, it is crucial to acknowledge that wetlands are a significant source of these gases. Brazil's Pantanal, the largest tropical inland wetland, includes numerous lacustrine systems with freshwater and soda lakes. This study focuses on soda lakes to explore potential biogeochemical cycling and the contribution of biogenic GHG emissions from the water column, particularly methane. Both seasonal variations and the eutrophic status of each examined lake significantly influenced GHG emissions. Eutrophic turbid lakes (ET) showed remarkable methane emissions, likely due to cyanobacterial blooms. The decomposition of cyanobacterial cells, along with the influx of organic carbon through photosynthesis, accelerated the degradation of high organic matter content in the water column by the heterotrophic community. This process released byproducts that were subsequently metabolized in the sediment leading to methane production, more pronounced during periods of increased drought. In contrast, oligotrophic turbid lakes (OT) avoided methane emissions due to high sulfate levels in the water, though they did emit CO2 and N2O. Clear vegetated oligotrophic turbid lakes (CVO) also emitted methane, possibly from organic matter input during plant detritus decomposition, albeit at lower levels than ET. Over the years, a concerning trend has emerged in the Nhecolândia subregion of Brazil's Pantanal, where the prevalence of lakes with cyanobacterial blooms is increasing. This indicates the potential for these areas to become significant GHG emitters in the future. The study highlights the critical role of microbial communities in regulating GHG emissions in soda lakes, emphasizing their broader implications for global GHG inventories. Thus, it advocates for sustained research efforts and conservation initiatives in this environmentally critical habitat.

Forest type modulates mammalian responses to megafires

Although considered an evolutionary force responsible for shaping ecosystems and biodiversity, fires' natural cycle is being altered by human activities, increasing the odds of destructive megafire events. Here, we show that forest type modulates the responses of terrestrial mammals, from species to assemblage level, to a catastrophic megafire in the Brazilian Pantanal. We unraveled that mammalian richness was higher 1 year after fire passage compared to a pre-fire condition, which can be attributed to habitat modification caused by wildfires, attracting herbivores and open-area tolerant species. We observed changes in assemblage composition between burned/unburned sites, but no difference in mammalian richness or relative abundance. However, by partitioning the effects of burned area proportion per forest type (monospecific vs. polyspecific), we detected differential responses of mammals at several levels of organization, with pronounced declines in species richness and relative abundance in monospecific forests. Eighty-six percent of the species presented moderate to strong negative effects on their relative abundance, with an overall strong negative effect for the entire assemblage. Wildfires are predicted to be more frequent with climate and land use change, and if events analogous to Pantanal-2020 become recurrent, they might trigger regional beta diversity change, benefitting open-area tolerant species.

Neotropical mammal responses to megafires in the Brazilian Pantanal

The increasing frequency and severity of human-caused fires likely have deleterious effects on species distribution and persistence. In 2020, megafires in the Brazilian Pantanal burned 43% of the biome's unburned area and resulted in mass mortality of wildlife. We investigated changes in habitat use or occupancy for an assemblage of eight mammal species in Serra do Amolar, Brazil, following the 2020 fires using a pre- and post-fire camera trap dataset. Additionally, we estimated the density for two naturally marked species, jaguars Panthera onca and ocelots Leopardus pardalis. Of the eight species, six (ocelots, collared peccaries Dicotyles tajacu, giant armadillos Priodontes maximus, Azara's agouti Dasyprocta azarae, red brocket deer Mazama americana, and tapirs Tapirus terrestris) had declining occupancy following fires, and one had stable habitat use (pumas Puma concolor). Giant armadillo experienced the most precipitous decline in occupancy from 0.431 ± 0.171 to 0.077 ± 0.044 after the fires. Jaguars were the only species with increasing habitat use, from 0.393 ± 0.127 to 0.753 ± 0.085. Jaguar density remained stable across years (2.8 ± 1.3, 3.7 ± 1.3, 2.6 ± 0.85/100 km2), while ocelot density increased from 13.9 ± 3.2 to 16.1 ± 5.2/100 km2. However, the low number of both jaguars and ocelots recaptured after the fire period suggests that immigration may have sustained the population. Our results indicate that the megafires will have significant consequences for species occupancy and fitness in fire-affected areas. The scale of megafires may inhibit successful recolonization, thus wider studies are needed to investigate population trends.

Plastic ingestion in giant tortoises: An example of a novel anthropogenic impact for Galapagos wildlife

The human population of Galapagos has rapidly increased in the last decades accelerating the anthropogenic pressures on the archipelago's natural resources. The growing human footprint, including inadequate management of garbage, may lead to conservation conflicts. Here, we assessed the ingestion of debris by Western Santa Cruz giant tortoises (Chelonoidis porteri) within human-modified and protected areas. Additionally, we characterized environmental debris and quantified tortoise abundance together with tortoise fecal samples. We processed a total of 6629 fecal samples along a gradient of anthropogenic disturbance based on human debris presence. We found 590 pieces of debris in samples within human-modified areas (mean of 3.97 items/kg of feces) and only two pieces in the protected area (mean of 0.08 items/kg of feces). Plastic waste was the predominant category in feces within the anthropic area (86.3%; n = 511), followed by cloth, metal, paper, synthetic rubber, construction materials, and glass. On average, the proportion of plastic was higher in feces (84%) than it was in environmental debris (67%), denoting that plastics are more readily ingested than other types of debris. We also found that green, white, and light blue plastics were consumed more often than their prevalence in the environment, suggesting color discrimination. Tortoise abundance was higher in the protected area when compared to the human-modified area; however, recapture rates were higher in anthropized landscapes which increases tortoise exposure to plastics and other human associated threats. Our results indicate that plastics are frequently consumed by tortoises in the polluted anthropic areas of western Santa Cruz, but scarce in protected areas. More research is needed to understand the negative impacts associated with plastics for Galapagos terrestrial species. We encourage local stakeholders to implement current policies limiting expansion of urban areas, plastic use, and improving waste management systems to minimize threats to human and animal health.

Unraveling the adaptive chemical traits of Rhamnidium elaeocarpum Reissek in response to fire in pantanal wetlands

We conducted a study on the effects of fire on Rhamnidium elaeocarpum, a widely distributed woody species found in the Pantanal wetlands, using LC-MS metabolomics, total phenolic and tannin content analysis, and thermogravimetric behavior. We sampled individuals from four groups: No Fire, Fire 2019, Fire 2020, and APD 20 (individuals whose aerial parts had died during the 2020 fire event). We found that recent fires had no significant impact on the species' phenolic metabolism except for those in the fourth group. These specimens showed a decline in secondary metabolites due to leaching. The high levels of phenolics in R. elaeocarpum suggest that this species has a biochemical tolerance to the stress caused by seasonal fires. Metabolomic profiling revealed the presence of proanthocyanidin oligomers, which protect against oxidative stress and post-fire environmental disturbances. However, the passage of fire also led to a high incidence of toxic karwinaphthopyranone derivatives, which could be a concern for the species' medicinal use. Finally, the thermogravimetric analysis showed that the species is thermotolerant, with an intrinsic relationship between the secondary compounds and thermotolerance. Our research has deepened the comprehension of how fire affects the metabolic processes of woody plants. The challenge now lies in determining if the identified chemical changes are adaptive characteristics that evolved over time or merely transient responses to external environmental stimuli.

Global conservation prioritization areas in three dimensions of crocodilian diversity

Crocodilians are a taxonomic group of large predators with important ecological and evolutionary benefits for ecosystem functioning in the face of global change. Anthropogenic actions affect negatively crocodilians' survival and more than half of the species are threatened with extinction worldwide. Here, we map and explore three dimensions of crocodilian diversity on a global scale. To highlight the ecological importance of crocodilians, we correlate the spatial distribution of species with the ecosystem services of nutrient retention in the world. We calculate the effectiveness of global protected networks in safeguarding crocodilian species and provide three prioritization models for conservation planning. Our results show the main hotspots of ecological and evolutionary values are in southern North, Central and South America, west-central Africa, northeastern India, and southeastern Asia. African species have the highest correlation to nutrient retention patterns. Twenty-five percent of the world's crocodilian species are not significantly represented in the existing protected area networks. The most alarming cases are reported in northeastern India, eastern China, and west-central Africa, which include threatened species with low or non-significant representation in the protected area networks. Our highest conservation prioritization model targets southern North America, east-central Central America, northern South America, west-central Africa, northeastern India, eastern China, southern Laos, Cambodia, and some points in southeastern Asia. Our research provides a global prioritization scheme to protect multiple dimensions of crocodilian diversity for achieving effective conservation outcomes.

Heatwaves and fire in Pantanal: Historical and future perspectives from CORDEX-CORE

The Pantanal biome, at the confluence of Brazil, Bolivia and Paraguay, is the largest continental wetland on the planet and an invaluable reserve of biodiversity. The exceptional 2020 fire season in Pantanal drew particular attention due to the severe wildfires and the catastrophic natural and socio-economic impacts witnessed within the biome. So far, little progress has been made in order to better understand the influence of climate extremes on fire occurrence in Pantanal. Here, we evaluate how extreme hot conditions, through heatwave events, are related to the occurrence and the exacerbation of fires in this region. A historical analysis using a statistical regression model found that heatwaves during the dry season explained 82% of the interannual variability of burned area during the fire season. In a future perspective, an ensemble of CORDEX-CORE simulations assuming different Representative Concentration Pathways (RCP2.6 and RCP8.5), reveal a significant increasing trend in heatwave occurrence over Pantanal. Compared to historical levels, the RCP2.6 scenario leads to more than a doubling in the Pantanal heatwave incidence during the dry season by the second half of the 21st century, followed by a plateauing. Alternatively, RCP8.5 projects a steady increase of heatwave incidence until the end of the century, pointing to a very severe scenario in which heatwave conditions would be observed nearly over all the Pantanal area and during practically all the days of the dry season. Accordingly, favorable conditions for fire spread and consequent large burned areas are expected to occur more often in the future, posing a dramatic short-term threat to the ecosystem if no preservation action is undertaken.

Increased burned area in the Pantanal over the past two decades

Wildfires are behaving differently now compared to other time in history in relation to frequency, intensity and affected ecosystems. In Brazil, unprecedented fires are being experienced in the last decade. Thus, to prevent and minimize similar disasters, we must better understand the natural and human drivers of such extreme events. The Brazilian Pantanal is the largest contiguous wetland in the world and a complex environmental system. In 2020, Pantanal experienced catastrophic wildfires due to the synergy between climate, inadequate fire management strategies and weak environmental regulations. In this study, we analyzed recent patterns and changes in fire behavior across the Pantanal based on land use and cover (LULC) classes. The inter-annual variability of the fire and land cover changes between 2000 and 2021 was assessed using BA from MCD64A1 V.6 product and LULC data from Landsat satellite. Our work reveals that fires in the Pantanal over the last two decades tended to occur more frequently in grassland than in others land cover types, but the 2020 fires have preferentially burned forest regions. Large fire patches are more frequent in forest and grasslands; in contrast, croplands exhibit small patches. The results highlight that a broad scale analysis does not reflect distinct localized patterns, thus stratified and refined studies are required. Our work contributes as a first step to disentangling the role of anthropogenic-related drivers, namely LULC changes, in shaping the fire regime in the Pantanal biome. This is crucial not only to predict future fire activity but also to guide appropriated fire management in the region.

Assessing Spatial Variation of PBL Height and Aerosol Layer Aloft in São Paulo Megacity Using Simultaneously Two Lidar during Winter 2019

This work presents the use of two elastic lidar systems to assess the horizontal variation of the PBL height (PBLH) and aerosol layer aloft in the São Paulo Megacity. These two lidars performed simultaneous measurements 10.7 km apart in a highly urbanized and relatively flat area of São Paulo for two winter months of 2019. The results showed that the PBLH differences display diurnal variation that depends on the PBL during daytime growth phases. Cloud and sea breeze effects control most of PBLH variation. In the absence of cloud and sea breeze, the maximum difference (~300 m) occurs in the rapid development stage and is due to topographic effects. When the PBL approaches its maximum daily value, it tends to level off with respect to the topography. In addition, it was presented a method that combines elastic lidar (to detect an aerosol layer) and satellite data (to classify such a layer from Aerosol Optical Depth (AOD) and Aerosol Index (AI) information) for the detection of biomass burning events. This methodology demonstrated that the variations caused by Biomass Burning in AOD and AI enable both the detection of aerosol plumes originating from biomass burning and the identification of their origin.