The Pantanal is the largest wetland of the world and one of the most important biodiversity hotspots in South America. An unprecedented ongoing megadrought is severely affecting its ecological functioning, flood pulse dynamics, and fire regime. Regarding this problematic, the present study generates reliable information about the following key issues: 1—Evolution and dynamics, 2—Origin and determinants, and 3—Forecast based on identified determinants and current trends. Results show that the evolution of the megadrought has been differentiable in both, space and time. As for its origin and determinants, Climate Change was ratified as one of the most important threats to the Pantanal, and to vast areas of South America, since a strong correlation was identified between megadrought’s dynamics and the occurrence of intense marine heatwaves at Northern Hemisphere oceanic waters, and more specifically, at the Northeast Pacific. Results also show that the megadrought is expected to continue at both the Pantanal and the surrounding Highlands, at least until December 2023. Thus, an intensification of fires risk, extending now to areas historically flooded or perhumid should be expected, concomitantly to a very negative impact on non-fire-resistant vegetation cover, as well as ecosystem functioning and biodiversity, perhaps even worse than those from 2020, widely covered by the international media.

Extreme El Niño events stand out not only because they have powerful impacts but also because they are significantly different from other El Niños. In Ecuador, such events are accountable for negatively impacting the economy, infrastructure, and population. Spatial–temporal dynamics of precipitation anomalies from various types of extreme El Niño events are analyzed and compared. Results show that for eastern Pacific (EP) and coastal Pacific (COA) El Niño types, most precipitation extremes occur in the first half of the second year of the event. Any significant difference between events becomes more evident at this stage. Spatially, for any event, 50 % of all extreme anomalies occurred at elevations < 150 m. The difference between events was significant when considering the altitude when reaching 80 % of all extreme anomalies: the eastern Pacific (EP) El Niño from 1997/98 (EP98) at 500 m, the El Niño from January to April 2017 (COA17) at 800 m, and the EP El Niño from 1982/83 (EP83) at 1000 m. Nevertheless, in some sectors of the Andean Cordillera, the El Niño–Southern Oscillation (ENSO) signal could be detected at 3200–3900 m. The distance to the coastline and the steepness of relief may play a determining role. At lowlands, anomalies are most severe in regions where the seasonality index is the highest. These results are useful at different decision-making levels for identifying the most appropriate practices reducing vulnerability from a potential increase in extreme El Niño frequency and intensity.

The observed continuous rise in the frequency of extreme heat events in South America (SA) poses a serious challenge for public health. However, there is a lack on the understanding of the large-scale and long-term variability and trends of thermal stress in this continent. Accordingly, here we developed the first comprehensive bioclimatology of thermal stress over SA during the past four decades. Consecutive heat stress hours were analyzed using the Universal Thermal Climate Index (UTCI) from ERA5-HEAT reanalysis according to the Köppen–Geiger climate classification and also focusing on the 31 most populated cities of SA. Results show an inland/coastline contrast and a marked latitudinal northward increase in the number of hours under heat stress. Heat stress hotspots are located mostly around the Amazon, northern and central parts of SA with 26–35% of the hours between 1979 and 2020 under strong heat stress. The annual number of hours within heat stress increased significantly between 1979 and 2020, varying from + 1.16 h/year to + 8.25 h/year depending on the Köppen–Geiger class. The past 20 years (2000 forward) presented not only more consecutive hours under heat stress than the previous two decades in all the analyzed cities, but also a higher persistence of such conditions. The bioclimatology of thermal stress developed here may provide important guidelines to decision-makers for exploring adaptation strategies to increase societal resilience.

Este artículo evidencia la dinámica espacio-temporal de eventos climáticos extremos, referidos estos a condiciones de precipitación con capacidad de generar bien sean inundaciones o severas sequías, en uno de los más importantes sistemas hidrológicos de la vertiente del Pacífico del Ecuador, la cuenca del río Portoviejo, en la provincia de Manabí. El análisis de las precipitaciones a través del Índice Estandarizado de Sequía Pluviométrica (IESP) permitió establecer que el 14,8 % de los meses entre 1971-2011 están vinculados a condiciones de precipitaciones moderadas a extremas asociados a eventosENOS, específicamente a temperaturas cálidas en la región Niño 1+2 del Pacífico. En relación a eventos extremos secos, estos tienden a correlacionarse con una elevada actividad de huracanes en el Caribe y de lluvias monzónicas en la India. En el sentido de evaluar situaciones de riesgo en la cuenca del río Portoviejo, así como planificar medidas de mitigación y/o adaptación que permita la sostenibilidad de sus actividades, es importante realizar seguimiento a las tendencias de distintas variables macroclimáticas.

Species distribution modelling has become instrumental in assessing the influence of environmental conditions on the occurrence or abundance of taxa. The set of environmental layers used for this purpose is a crucial aspect, for which different climate‐based (bioclimatic) datasets have been recently developed. These bioclimatic variables result from combinations of precipitation and temperatures surfaces. Here, we explored both the performance and possibility of improving some of the currently available bioclimatic databases, through an evaluation of the precipitation and temperatures surfaces used to generate them. For this purpose, we used a combination of statistic and graphic approaches. We focused on Brazil, not only due to its natural megadiversity, but also due to its continental size and orographic heterogeneity: an excellent ground for refining methods replicable elsewhere. We found a better match between the climatic data measured on‐field and Tropical Rainfall Measuring Mission (TRMM 3B43 v7) in the case of precipitation, and the surfaces provided by the National Oceanic and Atmospheric Administration (NOAA) in the case of temperatures, sources uncommonly used for species niche modelling. We gauge‐calibrated the best performing surfaces using machine‐learning algorithms and generated corrected surfaces that allowed us to create BrazilClim: a database of bioclimatic variables, based on improved primary surfaces, which will result in more assertive predicted distributions and more actual pictures of the species' ecological requirements for megadiverse Brazil, an approach replicable elsewhere. All primary and bioclimatic surfaces generated for this study may be freely downloaded.

Fire is a natural disturbance in the Neotropical savannas, and rather frequent in the relativelydry and well-drained seasonal savannas of the Brazilian Cerrado. The neighboring Pantanal, onthe other hand, is a seasonally flooded savanna and the largest wetland in the world (≈138,000km 2 ). Due to its wetter condition, fires in the Pantanal are much less frequent and spatiallyrestricted. But, given an ongoing extreme drought, the 2020’s fires in the Pantanal have beenunprecedented in extent and duration: About one third (≈45,000 km 2 ) of the area of thisimportant wetland has gone up in flames since last January. Regarding this historical drought,climate change has been identified as one of the most important threats to the Pantanal.Reductions in precipitation may cause significant disturbances in its ecological functioning,affecting hydrological, floodplain inundation dynamics, as well as fire regime. Climate changemodels from a recent study (Thielen et al. 2020, doi:10.1371/journal.pone.0227437) indicatethat, for the Pantanal, extended severe droughts are to be expected from the warming of SeaSurface Temperatures (SST) at Northern Hemisphere oceans.The present study analyses the spatial and temporal dynamics of precipitations during theseries 1981-2020 in the Upper Paraguay River Basin (UPRB), which comprises the Pantanal andthe neighboring Highlands, along with a co-evaluation of the SST trends at three oceanicregions from Northern Hemisphere. Precipitation anomalies were analyzed by mean of theStandardized Precipitation Drought Index (SPDI) based on the 1981-2010 climate normals.Results show that for the UPRB, negative precipitation anomalies occur in pulses lastingseveral years. A drought starting in 2019 has been the strongest and most extended on record,persistently reaching the Extremely Dry condition (SPDI≤-2.0) during 2020. As early as Mar,over 64% of the Pantanal is affected by such drought, and around 83% by Dec. For the UPRB,four distinctive groups of subregions were identified according to their temporal dynamics ofmean SPDI values, mainly during Sep2019/Feb2020 and Mar2020/Dec2020. Here, precipitationanomalies from southernmost subregions of the Pantanal were less intense and even notaffected by the drought.As for SST, the Northeast Pacific region (PAC-NE) showed the most important dynamics. In thisregion, SSTs have been anomalously warm since Jun 2019, with 64% of the time SSTAsurpassing the 90 th percentile: reaching the Heatwave condition. With a lead of one to twomonths, PAC-NE showed the strongest (and negative) correlation with precipitation at UPRB(r=-0.87) during Jan2019 to Dec2020. There is a significant trend for an increase in SST at theNortheast Pacific, a trend that will certainly generate a rather continuous Heatwave in PAC-NE.As a result, one expects an extension of the current extreme drought in the Pantanal area, atleast during 2021, and the intensification of fires with unprecedented duration and intensity,extending now to areas historically flooded or perhumid. Concomitantly, we predict a mostdefinite impact on non-fire-resistant vegetation cover, as well as ecosystem functioning andbiodiversity.