Climate change is a major threat to biodiversity, with impacts already being observed and even greater projected for the future (IPCC, 2021). The average global temperature has risen by 1.09 °C since the end of the 19th century, with unprecedented speed (IPCC, 2021). Temperature increases, changes in precipitation patterns, and increased frequency of extreme events can majorly impact ecosystems and biodiversity, as the climate is an important determinant of macroecological patterns of species distribution (Pearson and Dawnson, 2003). The Paris Agreement, signed in 2015 in the context of the United Nations Framework Convention, was an important reference for climate mitigation by setting international targets to limit the increase in global average temperature to well below 2 °C (UNFCCC, 2015).

Brazil is considered a megadiverse country, including biodiversity hotspots such as the Atlantic Forest and Cerrado (Myers et al., 2000), and some of the Global-200 ecoregions such as the Southwestern Amazonian and Rio Negro-Juruá Moist Forests and Pantanal Flooded Savannas (Olson and Dinerstein, 2002). Its impressive biodiversity makes Brazil an important target for conservation in the face of climate change. Increases in mean temperature are predicted country-wide, with more severe increases in the central and northern portions (Gutiérrez et al., 2021), especially in the Pantanal wetlands and the Amazon, the latter also with a great reduction in total precipitation (PBMC, 2013; Gutiérrez et al., 2021). Such rainfall reduction acts in synergy with deforestation, potentially leading to a worrisome savannization of the Amazon (PBMC, 2013; Castellanos et al., 2022). In the northeast portion of the country, climate change is already causing a decrease in rainfall in the Caatinga dry forests, which is expected to intensify in the near future, aggravating the water deficit in the region (PBMC, 2013; Gutiérrez et al., 2021; Castellanos et al., 2022). In addition to increases in temperature and reduction in rainfall in the northern part of the country, increases in the frequency and intensity of extreme rainfall events are forecasted across the country, especially towards the south within the Atlantic Forest and the Pampa grasslands (PBMC, 2013; Castellanos et al., 2022), together with an increase in fire-prone conditions in the Amazon, Caatinga and the Cerrado (Arias et al., 2021; Viegas et al., 2022). All these alterations intensify in the most severe climate change scenarios (known as ‘business as usual’), pointing to the urgency of climate mitigation and adaptation measures.

Until the early 2000s, there were very few studies on the likely impacts of climate change on Brazilian biodiversity (Vale et al., 2009). However, this literature has grown in the last decades, placing the Atlantic Forest as one of the best-studied biodiversity hotspots in the world on this topic (Manes et al., 2021; Manes and Vale, 2022). Some studies have identified severe negative impacts from climate change, such as a 37% reduction in tree richness in the Amazon (Gomes et al., 2019), while others have predicted possible benefits, such as a threefold increase in primate species’ ranges, also in the Amazon (Sales et al., 2020). It is time, therefore, for a synthesis of the knowledge produced on the likely impacts of climate change on Brazilian biodiversity, to derive general trends.

Here, we developed the first and most comprehensive systematic review of the predicted future impact of climate change on Brazilian biodiversity using a quantitative approach. We used Brazil as our case study due to the large number of studies on future climate change impacts on biodiversity, its great environmental heterogeneity, and its vast biodiversity. We obtained 20,177 risk projections for biodiversity, identifying biases and knowledge gaps, and quantifying predicted impacts under business-as-usual and Paris Agreement scenarios.

Our review identified a strong bias in the distribution of information country-wide (Table S6; Fig S1). The Atlantic Forest was the most studied biome (39% of studies), followed by the Amazon (17%) and Cerrado (15%, Fig. S1). Although the Atlantic Forest has been the focus of most studies in Brazil, we compiled far more risk projections for the Amazon (77% of effect sizes, Table S6), mainly due to Gomes et al. (2019), who projected the impacts on 4,935 plants in multiple scenarios (Fig. S1). About 1% of the risk projections assessed species whose distribution is not limited to a single biome (hereafter ‘widespread’). Only 0.5% of the risk projections were for the Caatinga, while the Pampa and Pantanal together also accounted for 0.5%, highlighting a knowledge gap. We identified substantial bias towards terrestrial species, with very little information for freshwater species (Fig. S1). Only five papers assessed impacts on coastal and marine biodiversity. These were removed because we considered this number too small to capture patterns in such a diverse environment. We also identified a clear bias towards plants and vertebrates (54% and 38% of data, respectively). Almost all of our dataset was classified as spatial change (99.5%), while diversity and habitat changes accounted for only 0.5%.

We classified the species with projected impacts as at risk of extinction, negatively impacted, or positively impacted. We evaluated 7,650 species for the BAU scenario and 7,515 for the Paris Agreement scenario. Although few species are expected to be positively impacted, most species are likely to experience negative impacts, with a considerable portion being at risk of extinction (Fig. 1; Table S6). Impacts varied according to taxon and biome, but there is a trend towards a greater number of negatively impacted species in the BAU scenario, with a much higher number of species predicted to be at risk of extinction than in the Paris Agreement scenario (from 14% to 25% in BAU; Figs. Fig. 11 and Fig. 22 , Table S7).

Fig. 1.

Percentage of risk projections of species at extinction risk, positively and negatively impacted in the future projections. We evaluated 7,650 species in the BAU scenario and 7,515 in the Paris Agreement scenario, but the total count is higher since a species can have different projections in different scenarios. The number of species at risk of extinction is higher in the BAU scenario.

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Fig. 2.

Different impacts of climate change on Brazilian biomes and taxa. Predictions are shown for business-as-usual (BAU) and Paris Agreement (Paris) scenarios. The columns represent the percentage of risk projections that are positive, negative, or indicating a potential extinction risk for each taxon in each biome. The numbers indicate the number of species affected. The figures represent the different taxon analyzed e.g., arthropods, birds, fishes, herpetofauna, mammals, and plants. AM = Amazon, CE = Cerrado, CA = Caatinga, PT = Pantanal, AF = Atlantic Forest, PP = Pampa.

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Overall, Brazilian biodiversity will likely be severely negatively impacted under the BAU scenario (−0.7%). However, the magnitude of these impacts is significantly reduced under the Paris Agreement scenario (−0.5%, p < 0.0001, t = −6.10) (Fig. 3, Table 1). The Paris Agreement will significantly reduce the magnitude of impacts from the BAU scenario for the Amazon (from −0.71% to −0.55%) (p < 0.0001, t = 16.77) and the Atlantic Forest (from −0.51% to −0.45%) (p < 0.0001, t = 16.77), the biomes with the most information available (Fig. 3, Table 1). For the other biomes, the very low number of projections precludes the identification of general trends. The projections suggest that the Pantanal will likely be the most negatively impacted biome under both the BAU scenario and Paris Agreement, albeit projections were almost exclusively for freshwater fishes (Fig. 3, Fig. S1). Similarly, the Paris Agreement did not significantly reduce impacts for Cerrado and Caatinga. Finally, the Pampa is the biome with the lowest projected impacts, which are even positive under the Paris Agreement, although not significantly so.

Fig. 3.

Climate change impacts on biodiversity for Brazil and each biome (mean ± 95% CI) in two scenarios. Negative numbers represent a detrimental impact, and positive numbers represent a beneficial impact of climate on biodiversity. Numbers in parentheses show the count of risk projections used to calculate the mean.

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We also found a significant difference in the impacts on invasive, endemic, and native species in Brazil (Fig. S2). Invasive species are predicted to suffer much smaller negative impacts than native and endemic species (p < 0.05; Table 1).

Projections also varied across taxa, with fish and arthropods as the most negatively impacted even under Paris Agreement scenarios, although with limited data, reducing confidence in results (Fig. S2). Contrastingly, taxa with the most available data, plants and birds, show a strong and significant reduction in impact under the Paris Agreement scenario compared to BAU (p < 0.0001). For mammals and herpetofauna, a decrease in impact was also observed, but it was not statistically significant.

Our analysis shows that commitment to the Paris Agreement is of utmost importance to reduce the negative impacts of climate change on biodiversity in Brazil. Although the Paris Agreement scenario will not be able to neutralize impacts down to zero, the mitigation policies may reduce the predicted negative impacts for Brazil by 21% while also cutting by half the number of species at risk of extinction from climate change. The Atlantic Forest and the Amazon are the biomes predicted to benefit the most from the Paris Agreement. The risks of not complying with mitigation strategies are very high, as shown by our results for the BAU scenario.

We reveal important taxonomic and geographic biases in studies projecting the impacts of climate change on Brazilian biodiversity. Despite 8,500 km of coast under considerable susceptibility to climate change (Manes et al., 2023), the shortage of studies on coastal and marine environments precluded their inclusion in our analysis. Even in terrestrial environments, there was a substantial disparity in studies, with biomes severely understudied (only 0.5% of risk projections for Pantanal and Pampa), and a strong bias towards the country’s rainforests (Amazon and Atlantic Forest) — a pattern that is surely associated with their greater biodiversity and appeal, but that leaves other important environments unattended, with dire consequences for biodiversity conservation in the face of climate change (Overbeck et al. 2015; Fernandes et al. 2023). We also found a strong taxonomic bias towards plants and terrestrial vertebrates that, together, represent >90% of our dataset, whereas the very few studies on invertebrates and aquatic fauna reveal an important knowledge gap and stress the need for more studies in such underrepresented taxa. These biases hinder the formulation of efficient climate adaptation strategies for Brazil’s astonishing biodiversity.

Climate change impacts varied across the Brazilian biomes. Pantanal presented the highest projected impact rates, which is strongly associated with risks towards freshwater fishes (93% of risk projections). Notably, this very severe prediction loses some strength due to the small number of risk projections on fish and due to the lack of papers evaluating more distinct taxa. Thus, further studies should assess the potential impacts on Pantanal’s biodiversity, especially since it is one of the largest wetlands in the world (Harris et al., 2005) and is currently suffering from severe changes in rainfall (Lázaro et al., 2020), leading to severe droughts and increasing the frequency of wildfires (Viganó et al., 2018; Marques et al., 2021; Viegas et al., 2022). The severe negative impact on Brazilian rainforests, the Amazon and Atlantic Forest, is extremely worrisome since they harbor high biodiversity. Although the Amazon still maintains ∼80% of its native vegetation cover (Souza et al., 2020), which increases its resilience, the biome is highly threatened by ongoing deforestation and its high climatic hazard. The Amazon is likely to suffer the greatest temperature increases in Brazil (Gutiérrez et al., 2021) and associated changes in rainfall patterns concomitant to increasing deforestation can lead to a replacement of tropical rainforest by savannah vegetation (PBMC, 2013; IPCC, 2022), representing a complete shift in the Amazon’s structure. Contrastingly, the Atlantic Forest is not predicted to suffer such severe changes in climate, although increases in temperature and changes in rainfall patterns are likely (PBMC, 2013; Gutiérrez et al., 2021). Nonetheless, the risks to the Atlantic Forest are heightened as only 28% of its forest cover remains, fragmented into small and isolated patches (Rezende et al., 2018; Ribeiro et al., 2009), reducing its resilience to predicted environmental changes. The severe fragmentation in this biome should also hinder species range shifts (Opdam and Wascher, 2004), making one of the main responses of biodiversity to climate change unfeasible (Bellard et al., 2012). Lastly, the mildest projected impacts for the Pampa are coherent with the climate hazard projected for the region, which will likely have the lowest temperature increases in Brazil.

Given the severe predicted impacts, our findings emphasize the imperative nature of climate change mitigation measures. While the negative impact of climate change on biodiversity under Paris Agreement scenario does not drop to zero, mitigation efforts have the potential to significantly reduce these impacts. The importance of limiting temperature increase to reduce climate change’s impacts on biodiversity has already been demonstrated in regional to global scale studies (e.g. Manes et al., 2021; Manes and Vale, 2022, and Warren et al., 2018). To achieve greater biodiversity conservation, however, we need to combine strong mitigation with adaptation measures, such as expansion and adaptation of protected areas in the context of climate change (Malecha et al., 2023; Manes and Vale, 2022). Certainly, this must be a truly international movement with active engagement particularly from nations that have significantly contributed to the climate crisis (i.e., the developed countries), as implementing measures within a single country cannot resolve the climate crisis. Each nation must propose and genuinely fulfill its commitments, enabling the international community to achieve an overarching global goal. The latest Brazilian Nationally Determined Contribution (NDC) prepared in 2024 commits to reducing greenhouse gas emissions by 59–67% by 2035, with the goal of achieving carbon neutrality by 2050 (Brazil, 2024). To achieve these goals, the Brazilian NDC includes several actions that have clear co-benefits to biodiversity, increasing its resilience to climate change. These include, for example, the elimination of illegal deforestation by 2030 (mostly in the Amazon) and the restoration of 24 Mha of degraded areas by 2050, showing the synergy between climate mitigation and adaptation so common in nature-based solutions. Brazil's National Adaptation Plan also encourages the production of knowledge about the impact of climate change on biodiversity. The synthesis provided here contributes to the development of adaptation strategies with a focus on biodiversity conservation. These strategies are needed to protect Brazil’s biodiversity and increase people’s resilience to climate change. Changes in the hegemonic over-exploitative development model are necessary and viable (IPCC, 2022), and are the only path to move towards a sustainable future.