Wildfires disproportionately affected jaguars in the Pantanal

Global climate change combined with regional and local anthropic activities suggest an increase in recurrence and extent of wildfires on ecosystems worldwide^31,47,48, affecting in particular regions with higher likelihood of fire occurrences³¹ and making natural systems more prone to fire occurrences²¹. Estimates of accumulated burned area in Brazil between 1985–2020 revealed that, among the Brazilian biomes, the Pantanal is the most affected by the fires (with accumulated burned area equivalent to 57.5% of the biome within Brazil)⁴⁶. But 43% of 2020 burned area (≈13% of the Pantanal) had not burned since 2003¹⁹. Therefore, it is impressive that nearly 1/3 of the Pantanal burned in a single year^17,18,19 (Figs. 1, 2 and S1, S2). The high number of human-induced fires^17,18,19,21 combined with the hottest and driest conditions since 1980^17,22,38,49 led 2020 to record the highest daily severity rating (DSR) index of fires for this time period^17,49. With documented increase of 2 °C in the average temperature²² and a 40% shortage in rainfall^26,38. But the fire risk got even higher with the simultaneous occurrence of dry and hot spells, between August and November, when the maximum temperature reached, on average, 6 °C above the normal, accounting for 55% of the burned area of 2020⁴⁹.

Most fires started close to the agriculture frontiers²¹, but they predominantly affected the natural vegetation (reaching between 91–95% of it in occurrence of fire^50,51 and 96% of it in estimated burned area)^31,46, with tragic consequences for jaguars and the Pantanal biota^17,19,26. Along with the fires, the severity of the 2020 drought^22,52,53 dropped minimum river depths at around 86% below normal^25,54 (Fig. 2 and S1, S3, S4). Consequently, resulting in several records of animal starvation, dehydration, and death^17,19,26. And late mortality from indirect causes of fires certainly increased these numbers²⁶. Besides, post-fire ecosystem and hydrology changes also had ecological effects with long-term impacts on ecosystem recovery and fire risk³¹, impacting resource quality, availability, and productivity^26,31. Vegetation productivity declined below −1.5 σ over more than 30% of the natural areas and evaporation decreased (by ~ 9%)³¹. Burned vegetation made the soil more vulnerable to erosion, increasing the runoff (by ~ 5%) over the natural areas³¹, and the resulting charcoal and ash contaminated rivers¹⁷.

Many reasons may have contributed to the intensity of the 2020 drought in the Pantanal, from climate^8,22,24,49 to direct and indirect human impacts in the Upper Paraguay River Basin (UPRB)^21,55,56. In fact, anthropic changes in land use also increased the biome sensitivity to fire-climate extremes)³¹. The shortage of rain throughout the UPRB, particularly in the summer season, is among the main factors, as the basin water balance controls the hydroclimatological dynamics in the Pantanal (Fig. 2 and S3–S9)²². The shortage of rain may also be a consequence of increased deforestation in the Amazon rainforest^57,58, as summer rainfall in the Pantanal is strongly associated with the climate of the Amazon⁵⁹. Furthermore, the reduction in wetland flooded areas is historically correlated with the spread of fires (Fig. 2 and S1)^22,28,29. Low water levels led to the absence of flooding and reduced wetland areas, and the remaining dry vegetation provided flammable material and created favourable conditions for fires to occur^22,23,24. In addition, the lack of governmental and human resources and delayed response at federal and local levels^58,60,61 amplified the negative effects of water shortage^17,19,58.

Although historical hydrological series show that extreme drought events occurred in the past^22,25,38,62 (e.g., from the late 1960s to early 1970s, Fig. S3), they also show that the recovery of the Pantanal was conditioned to the subsequent 15 years of regular to exceptional floods (1974 to early 1990s, Figs. S1, S3). Savanna-like vegetation, the predominant vegetation type in the Pantanal, usually recovers from the effects of fires in relatively short periods (months to a few years)²³, depending on the severity and frequency of fires and climate conditions in the subsequent years^23,28,29. But the resilience of many species may decrease with the annual repetition of extreme fire events^28,29,30. Thus, human interventions to prevent (instead to promote) sequential fire events in the same area are paramount^19,23,62,63.

Estimating the effects that uncontrolled extensive fires can cause to the apex predator of the Neotropics in a region considered one of the strongholds for the species can contribute to the conservation of jaguar and other wildlife species, as well as to the debate regarding potential cumulative impact of recurrent wildfires on ecosystems^{26,31,51,62,63}. Our results revealed the drastic impact of fire on estimated numbers of jaguars, home ranges, and priority areas for jaguar conservation in the Pantanal was exceptionally high in 2020 and proportionally more severe than the nominal 31% of burned area across the Pantanal (e.g., fires affected 45% of the jaguars and 79% of their HRs). Moreover, the annual comparison showed that 2019 was the second-worst year regarding fire impacts (only behind 2020) and equally extreme compared to historical means²². Although the Pantanal is well known for its annual and pluri-annual cycles of wet and dry seasons^7,64, the unusual levels of droughts^22,25,65,66 and fires^17,20,21 in subsequent years are alarming. Furthermore, climate assessment and projections of warmer and dryer conditions for the region in the coming years are equally worrying^22,24,37,38.

We found that 45% of the jaguar population estimated for the Pantanal occupied areas affected by the 2020 fires (Fig. 1). This finding suggests that the fires heavily impacted the jaguars in the Pantanal, even if we assume that the major effects were only temporary displacement. This potential displacement may make it more difficult for jaguars to find new suitable areas, thus increasing territorial disputes and decreasing survival and reproductive success. Furthermore, 2019 ranked as the second-highest year of impact of fire on jaguar population estimates among the 16 years considered (Table 1, Fig. 1). Importantly, we did not consider cumulative impacts on sequential years or fire recurrence in these estimates. Moreover, the available estimates for jaguar abundance we used³⁶ are very conservative and probably underestimated jaguar populations from the Pantanal by a maximum of 3 jaguars/100 km². However, the reported density of jaguars may reach up to 12.4 jaguars/100 km² in northern PAs^5,67,68 and up to 6.5–7 jaguars/100 km² in the southern Pantanal farms^5,69,70. Considering that PAs in the northern Pantanal were severely damaged by the 2020 fires, our results show conservative figures for the actual number of jaguars affected by fires.

We used densities estimated from an ecosystem-wide assessment of impacts as a proxy of the proportion of total population reached by fire each year on a regional scale. Fires affected a substantial proportion of estimated individuals in the Pantanal in 2019–2020. In 2020, for instance, 87% of all jaguars affected by fire were in the Brazilian Pantanal. In contrast, the smaller population in the Paraguayan and Bolivian Pantanal had a higher median percentage of individuals affected by fire between 2005–2019. While 45% of jaguars were affected by fire in a single year (2020) in the Pantanal, a study⁴⁵ using the same conservative estimates³⁶ for jaguar abundance in the Brazilian Amazon revealed that 1.8% of the population (1422 individuals) was killed or displaced by fire between 2016–2019. Another report estimated that more than 500 individuals were affected by the 2019 fires in the Brazilian and Bolivian Amazon^71,72. Based on the same density estimates we found that in the Pantanal — a much smaller biome — more jaguars were affected by fire in single years (n = 513 in 2019 and n = 746 in 2020). This recent increase in the number of jaguars affected by fire raises a red flag to the supposed stability of the species in the Pantanal, which is currently globally and locally classified as Near Threatened^1,5. Therefore, we recommend that future assessments by IUCN specialists carefully consider the frequency and intensity of fires as a potentially significant and growing threat to jaguars in the Pantanal, and their effects on long-term populational trends.

Quantifying the occurrence of fire on HRs introduced a functional perspective to understanding the impact of fire on individual jaguars. Similarly, our estimates of the number of affected jaguars revealed a vast amount and extent of affected HRs in the last two years (Figs. 2 and 3). Jaguars are apex predators, often considered as a keystone^73,74,75,76 and umbrella species^45,77, highly dependent on large habitat areas⁷⁸, dense native vegetation cover^35,79,80, and abundance of prey^67,81. Considering that jaguars often select areas with high environmental integrity^{35,68,78,79,80}, the higher impact of recent fires on HRs corroborates reports showing the increase of natural areas burned in the Pantanal^31,46,50,51. The proportion of burned forests, for instance, was 10 times higher in 2020 than the estimated median between 1985 and 2019³¹. Sadly, it is likely that much of these burned forests in Northern Pantanal included areas pointed as suitable jaguar habitat and of great interest to the creation of additional PAs⁸².

In the Pantanal, HRs are smaller^35,83 and population densities are high^{5,67,68,69,70} because the biome is a highly productive system^7,55,67, with an abundance of prey species and quality habitat, thus allowing jaguars to meet their spatial needs using smaller areas^35,68,83. Consequently, floodplain jaguars are also usually larger^44,84. However, a trend of increasing drought, rising temperatures, and repeated occurrences of exceptional fires would weaken the Pantanal’s resilience^22,32. Importantly to note as well that the occurrence and intensity of fires are frequently higher in the dry season, peaking within jaguars HRs in the years with intense fire occurrence in the Pantanal. This apparent higher impact over jaguar habitat agrees with studies pointing out highest damage in PAs^17,27 (Fig. S20), natural vegetation and particularly in forested areas in 2020^31,46,50,51. Recurrent impacts may particularly affect the most sensitive species^28,29,30, resulting in a less productive environment³², which ultimately decreases the habitat quality of many species. These effects would likely push jaguars to expand their HRs, which would increase disputes for territories and favour a decrease in body size, consequently decreasing reproductive rates and population size.

The extent of protected areas burned is another indicator of how fire can impact biodiversity. Like the HRs, the Pantanal PAs were affected differently in space and time, but the greatest fires occurred in recent years (2019 and 2020). In 2020, fires occurred in 62% of Brazilian PAs — particularly in northern Pantanal — where several portions of PAs overlapping with jaguar HRs were entirely or almost entirely affected by fires (Figs. 1–3). In 2019, however, fires affected the Pantanal PAs in Bolivia, Paraguay and southern Brazil more severely in areas that also overlapped with HRs (Figs. 1–3). Several causes can explain the spread of fires across PAs, including a combination of heat, drought, miscalculated human use of fires, lack of resources and personnel for surveillance and fire control improvement^{17,18,19,20,21,22,23}.

The displacement, injuries, and deaths caused by fire to animals within PAs are worrying because these areas are reportedly richer in diversity and biomass^85,86 (including higher jaguars densities^36,67,87 and are fundamental to safeguarding biodiversity and ensuring the long-term provision of ecosystem services^88,89. Protected areas are important to jaguars because they provide larger continuous areas of natural dense vegetation cover (such as forests and shrublands), flooded habitats and limit contact with humans, attributes of great influence in jaguar habitat selection^{35,78,79,80,82}, and particularly important to females^90,91. However, although some PAs support up to 12.4 jaguars/100 km² (e.g., Taiamã Ecological Station – TES)⁶⁷, the currently availability of Pantanal PAs alone would not support viable jaguar populations for more than 50 years⁸⁷. Therefore, sustainable management that allows coexistence in private lands is also fundamental for the conservation of jaguars in the Pantanal^5,9,10,11. Protected areas of integral protection, such as TES, currently occupy only 5.7% of the Pantanal⁷ but were the most affected by fires in absolute area (Fig. S20, Table S5)²⁷. The total number of PAs, including the sustainable use ones, corresponds to only 5% of the Brazilian Pantanal (Tables S1–S3)^{7,92,93,94,95,96} and around 10% of the entire Pantanal⁷, most of it in Bolivia⁹⁷. These percentages are much lower than the minimum of 17% recommended in the Aichi goals for terrestrial ecosystems^7,56. Furthermore, PAs are also scarce in the Pantanal headwaters (6% of the surrounding Cerrado uplands) (Tables S1–S3, Fig. S19)^{7,92,93,94,95,96}. To make matters worse, PAs were reduced by almost 20% in the Brazilian Pantanal in 2007 and have not been expanded in the Cerrado uplands since 2006 (Tables S1–S3, Fig. S19)⁹³. The relatively small coverage of protected areas in the Pantanal, which serve as refuges, increases the negative effects of fires, as jaguars are likely displaced into sub-optimal habitats. Consequently, jaguars and other species may struggle to find equally resource-rich sites after being displaced from PAs.

For the long-term survival of the jaguar, it is essential to implement conservation plans that consider the dispersal and reproduction of the species along the Paraguay River⁹⁸, increase the network and size of PAs⁸², and adequately allocate funding and personnel to maintain the PAs. Furthermore, careful implementation of strategies to mitigate the risk of fire^18,19,62 and other human impacts outside PAs^{5,6,7,8,9,10,11,12,13,14,15,16,89,99} are urgent needs for conservation of the Pantanal. In any case, our results highlight that to sustain viable populations of jaguars and other species, conservation plans for the Pantanal must account for fire impact on PAs and other vital areas for biodiversity.

Although jaguar HRs often overlap with PAs^67,68,87, some individuals may settle in unprotected areas^69,70. In our sample, we found that 38 HRs partially overlapped with PAs (Fig. 1) and 10 HRs did not. On the other hand, considering the sum of the HR extents and the total area overlapped with the PAs, we found that 20% of the HR extent matched the PAs. Notably, jaguars coexist with different levels of anthropic pressures outside the PAs^{4,5,9,10,11,12,13,14,15,16}. Jaguar distribution range has been restricted to 63% of the Pantanal⁵ and even more restricted in the UPRB¹⁰⁰. Agriculture expansion, particularly cattle ranching and soybean cultivation (Figs. S17, S18)⁶⁵, has been identified as the main causes of jaguars’ disappearance or decline due to killing and habitat loss^5,9,13.

Sustainable use has been advocated as a conservation strategy in the Pantanal, mainly due to the characteristics of the region, where cattle ranching uses as pastures the natural areas restricted by the Pantanal flooding regime since the 17th century^7,23. In recent years, ecotourism has also gained great importance^55,101,102. However, there are risks in relying on sustainable use as a core strategy for 90% of the biome (95% of Brazilian Pantanal), and exposure to human-induced fires is one of them^21,31.

Fire is a fundamental factor acting on the dynamics of the Pantanal vegetation^23,28,29. However, repeated uncontrolled fires can drastically impact forests and other habitats critical to the jaguars and increase the area for cattle ranching, therefore increasing the risk of livestock depredation and retaliatory hunting¹¹. Thus, the conservation of the jaguar and other animal species in the Pantanal is critically linked to fire management and the use of private lands because the increased fire may extend and aggravate other anthropic impacts (Fig. 4). This work highlights the significant increase in the extent and severity of recent fires in the Pantanal and how these fires have affected jaguars. Further studies that estimate natural habitat recovery and fire recurrence and assess real-time and long-term effects of fire on jaguars and other species are critical to guide fire management and conservation.

Changes in the climate^{8,22,24,37,38}, landscape and water use in the UPRB over the last four decades^7,18,56,65 are cumulative threats that may interfere with water recharge and vegetation resilience in the Pantanal. Global temperatures may increase up to 1.5 °C over the next five years³⁷, in addition to the 2 °C already recorded since 1980. By the end of the 21st century, scientists estimate increases of 5 − 7 °C in the temperature and the frequency of climatic extremes and a 30% reduction in average rainfall^8,37,38. Until 2019, pastures covered 15.5% of the Brazilian Pantanal and agriculture about 0.14%²⁵. However, agriculture and pastures occupied 60–65% of the surrounding Cerrado uplands within the UPRB^7,55,56, an occupation similar to the adjacent Paraguayan Chaco and Bolivian Chiquitano Forest^7,103,104. And future projections estimate a loss of 14,005 km² of native vegetation from 2018 through 2050¹⁰⁵. Consequently, this land occupation impacted the main headwaters of the Pantanal rivers and ultimately the entire Pantanal^6,56,106,107. Furthermore, by 2019, 47 hydroelectric power plants were installed or in operation, and another 133 were planned, totalling about 180 potential dam projects in the Brazilian UPRB¹⁰⁸. Besides, most of these projected hydropower infrastructures will overlap with the distribution of jaguars, also in the adjacent biomes, impacting negatively the species particularly in Brazil¹⁵. These economic and infrastructure activities in the surrounding highlands frequently ignore their cumulative impacts¹⁰⁹ and affect the Pantanal in different ways (Fig. 4, S17, S18), including its drainage dynamics and flood pulses, with consequent impacts on drought duration and fire spread^{17,19,22,23,24}(Figs. 1–4, SI). This combination of factors probably intensifies the Pantanal droughts, particularly the periodic sequence of dry years.

Therefore, a critical point is how human actions can exacerbate such extreme events^{7,21,31,55,106,110} and make fire control even more difficult^19,23,62 or, on the opposite, contribute to minimize the overall impacts of drought and fires and promote biodiversity conservation^19,63 (Fig. 4). Given that the rainfall remained below average in the last wet seasons⁵³ (Figs. S1, S3–S8) and that a severe drought persisted in 2021¹¹¹, a surveillance protocol for rapid response and programs for fire management, mitigation of human impacts and ecosystem recovery are needed^19,23,62,63. If such measures keep lacking, a tragedy similar to the 2020 fires may be repeated in the coming years (Fig. 4). And Pantanal native vegetation may be reduced to only about 62% by 2030²¹. To make matters worse, the government budget allocated for fire control and firefighting for 2021 was reduced to 65.5% of the 2019 budget⁶¹ and all funds allocated to the environment were reduced to the lowest level in 20 years^61,112, with serious complaints of misuse¹¹³, embezzlement¹¹⁴ and wood-smuggling probe¹¹⁵.

The extent of the recent wildfire in the Pantanal has signalled that fire is a potential threat to the long-term conservation of the jaguar. Furthermore, fires severely affected other species and human activities^17,19,23, demanding an immediate mitigation plan^18,19,62. In fact, permanent fire brigades have been established, and an animal rescue centre is under construction in response to the effects of the recent extensive fires in the Pantanal. Although actions are underway at local levels, the warming and drying trend^22,24,37,38 is also a combination of global warming^8,37 and rapid land-use changes^7,18,65 (Figs. S17, S18), with cumulative impacts in the UPRB and Pantanal wetlands (Fig. 4). Therefore, the immediate reduction of deforestation in the Amazon and Pantanal and the establishment of a forest restoration plan in the UPRB are critical. The lack of sufficient mitigatory actions may throw the Pantanal into a perverse vortex (increasing feedback of cumulative negative impacts, (Fig. 4), thus affecting the survival of jaguars and the various species under their umbrella, as well as human welfare.

Source: Ecology - nature.com