Explore the vast range of titles available.

The possibility that the Amazon forest system could soon reach a tipping point, inducing large-scale collapse, has raised global concern 1 – 3 . For 65 million years, Amazonian forests remained relatively resilient to climatic variability. Now, the region is increasingly exposed to unprecedented stress from warming temperatures, extreme droughts, deforestation and fires, even in central and remote parts of the system 1 . Long existing feedbacks between the forest and environmental conditions are being replaced by novel feedbacks that modify ecosystem resilience, increasing the risk of critical transition. Here we analyse existing evidence for five major drivers of water stress on Amazonian forests, as well as potential critical thresholds of those drivers that, if crossed, could trigger local, regional or even biome-wide forest collapse. By combining spatial information on various disturbances, we estimate that by 2050, 10% to 47% of Amazonian forests will be exposed to compounding disturbances that may trigger unexpected ecosystem transitions and potentially exacerbate regional climate change. Using examples of disturbed forests across the Amazon, we identify the three most plausible ecosystem trajectories, involving different feedbacks and environmental conditions. We discuss how the inherent complexity of the Amazon adds uncertainty about future dynamics, but also reveals opportunities for action. Keeping the Amazon forest resilient in the Anthropocene will depend on a combination of local efforts to end deforestation and degradation and to expand restoration, with global efforts to stop greenhouse gas emissions. Analyses of drivers of water stress are used to predict likely trajectories of the Amazon forest system and suggests potential actions that could prevent system collapse.

Past human societies have left persistent marks on forests worldwide. However, the degree to which pre-colonial Amerindian societies have affected forest structure is still not fully understood, especially in southern Brazil. This study investigated the influence of two distinct Amerindian groups (Southern-Jê and Guarani) over tree composition of forest fragments in the State of Santa Catarina. Vegetation data was obtained from the Santa Catarina Forest and Floristic Inventory (SCFFI): a statewide systematic vegetation sampling project. Archaeological data was collated from literature reviews as well as existing databases for archaeological sites occupied by Guarani and Southern-Jê groups. Using these sites of known Amerindian occupation, and corresponding environmental variables, ecological niche models were developed for each Amerindian group, predicting potential archaeological sites occupied by these groups across southern Brazil. Maps of these potential occupation sites of pre-colonial Amerindian groups were compared with 417 corresponding floristic inventory plots. Redundancy analysis (RDA) was used to identify floristic composition patterns linked to areas with a high probability of Southern-Jê or Guarani presence. Southern-Jê and Guarani pre-colonial occupations overlapped near main rivers; however, Southern-Jê groups generally occupied elevated areas whereas Guarani occupied mostly coastal areas. We observed differences in forest composition associated with the predicted occurrence of these pre-colonial Amerindian groups. Based on these results, we argue there is a relationship between tree species distribution and pre-colonial human occupation by these two Amerindian groups.

The legacy of pre-Columbian land use in the Amazonian rainforest is one of the most controversial topics in the social 1 – 10  and natural sciences 11 , 12 . Until now, the debate has been limited to discipline-specific studies, based purely on archaeological data 8 , modern vegetation 13 , modern ethnographic data 3 or a limited integration of archaeological and palaeoecological data 12 . The lack of integrated studies to connect past land use with modern vegetation has left questions about the legacy of pre-Columbian land use on the modern vegetation composition in the Amazon, unanswered 11 . Here, we show that persistent anthropogenic landscapes for the past 4,500 years have had an enduring legacy on the hyperdominance of edible plants in modern forests in the eastern Amazon. We found an abrupt enrichment of edible plant species in fossil lake and terrestrial records associated with pre-Columbian occupation. Our results demonstrate that, through closed-canopy forest enrichment, limited clearing for crop cultivation and low-severity fire management, long-term food security was attained despite climate and social changes. Our results suggest that, in the eastern Amazon, the subsistence basis for the development of complex societies began ~4,500 years ago with the adoption of polyculture agroforestry, combining the cultivation of multiple annual crops with the progressive enrichment of edible forest species and the exploitation of aquatic resources. This subsistence strategy intensified with the later development of Amazonian dark earths, enabling the expansion of maize cultivation to the Belterra Plateau, providing a food production system that sustained growing human populations in the eastern Amazon. Furthermore, these millennial-scale polyculture agroforestry systems have an enduring legacy on the hyperdominance of edible plants in modern forests in the eastern Amazon. Together, our data provide a long-term example of past anthropogenic land use that can inform management and conservation efforts in modern Amazonian ecosystems. Fossil records suggest that the Amazon rainforest in the pre-Columbian era was home to polyculture agroforestry, with multiple annual crops providing subsistence for indigenous groups who shaped the Amazon as early as 4,500 years ago.

The expansion of globalized industrial societies is causing global warming, ecosystem degradation, and species and language extinctions worldwide. Mainstream conservation efforts still focus on nature protection strategies to revert this crisis, often overlooking the essential roles of Indigenous Peoples and Local Communities (IP&LC) in protecting biodiversity and ecosystems globally. Here we assess the scientific literature to identify relationships between biodiversity (including ecosystem diversity) and cultural diversity, and investigate how these connections may affect conservation outcomes in tropical lowland South America. Our assessment reveals a network of interactions and feedbacks between biodiversity and diverse IP&LC, suggesting interconnectedness and interdependencies from which multiple benefits to nature and societies emerge. We illustrate our findings with five case studies of successful conservation models, described as consolidated or promising ‘social–ecological hope spots’, that show how engagement with IP&LC of various cultures may be the best hope for biodiversity and ecosystem conservation, particularly when aligned with science and technology. In light of these five inspiring cases, we argue that conservation science and policies need to recognize that protecting and promoting both biological and cultural diversities can provide additional co-benefits and solutions to maintain ecosystems resilient in the face of global changes. This Review identifies and describes interactions and feedbacks between biodiversity and diversity of Indigenous Peoples and Local Communities, and uses case studies from South America to illustrate the conservation and human benefits that can arise from protecting both biological and cultural diversity.

The Brazil nut tree (Bertholletia excelsa) is an iconic and economically valuable species that dominates vast swathes of the Amazon Basin. This species seems to have been an important part of human subsistence strategies in the region from at least the Early Holocene, and its current distribution may be a legacy of past human settlement. Because B. excelsa is a long-lived pioneer tree it requires natural or human disturbances to increase light availability in the understory for a successful establishment. However, it remains unclear how the long-term population dynamics of this species have been shaped by pre-colonial and post-colonial human practices. Here, we use tree-ring analyses to look at changes in growing conditions over the past 400 years in a Brazil nut tree population in Central Amazonia. We identify changes in tree recruitment and growth rates associated not only with regional climatic variability, but also major political and socio-economic activities recorded by historical documents in the vicinity of Manaus. We demonstrate that the expansion of a post-colonial political center (Manaus) from the middle of the 18th century onwards coincided with a reduction in recruitment of B. excelsa. We argue that this hiatus suggests the interruption of indigenous management practices, probably due to the collapse of pre-Columbian societies. A second recruitment pulse, and unprecedented cycles of growth release and suppression, aligns with a shift to modern exploitation of the forest into the 20th century. Our findings shed light on how past histories of human-forest interactions can be revealed by the growth rings of trees in Amazonia. Future interdisciplinary analysis of these trees should enable more detailed investigation of how human forest management has changed in this part of the world, through pre-colonial, colonial, and industrial periods of human activity, with potential implications for conservation.

Plants have been used in Amazonian forests for millennia and some of these plants are disproportionally abundant (hyperdominant). At local scales, people generally use the most abundant plants, which may be abundant as the result of management of indigenous peoples and local communities. However, it is unknown whether plant use is also associated with abundance at larger scales. We used the population sizes of 4,454 arboreal species (trees and palms) estimated from 1946 forest plots and compiled information about uses from 29 Amazonian ethnobotany books and articles published between 1926 and 2013 to investigate the relationship between species usefulness and their population sizes, and how this relationship is influenced by the degree of domestication of arboreal species across Amazonia. We found that half of the arboreal species (2,253) are useful to humans, which represents 84% of the estimated individuals in Amazonian forests. Useful species have mean populations sizes six times larger than non-useful species, and their abundance is related with the probability of usefulness. Incipiently domesticated species are the most abundant. Population size was weakly related to specific uses, but strongly related with the multiplicity of uses. This study highlights the enormous usefulness of Amazonian arboreal species for local peoples. Our findings support the hypothesis that the most abundant plant species have a greater chance to be useful at both local and larger scales, and suggest that although people use the most abundant plants, indigenous people and local communities have contributed to plant abundance through long-term management.

[This corrects the article DOI: 10.1371/journal.pone.0235819.].

In this essay, we will present arguments for a negative answer to the debate question: “ Is publishing ethnobiology data respectful of Indigenous and Local Knowledge holders’ rights? ” We recognize that ethnobiological research has advanced in recognizing the rights of Indigenous Peoples and Local Communities (IPLC), but we believe that we still have a long way to go in deconstructing colonialism in ethnobiology. In order to be truly respectful, ethnobiologists need to collaborate with IPLC to achieve an ethical science with equity between knowledge systems, fostering the co-production of knowledge from an intercultural science perspective. This essay was written by a group of Brazilian scientists, both IPLC and non-IPLC, and reflects a perspective of the academic universe seen from the place we are, in this multicultural and imbalanced world.

The Neolithic Revolution narrative associates early-mid Holocene domestications with the development of agriculture that fueled the rise of late Holocene civilizations. This narrative continues to be influential, even though it has been deconstructed by archaeologists and geneticists in its homeland. To further disentangle domestication from reliance on food production systems, such as agriculture, we revisit definitions of domestication and food production systems, review the late Pleistocene–early Holocene archaeobotanical record, and quantify the use, management and domestication of Neotropical plants to provide insights about the past. Neotropical plant domestication relies on common human behaviors (selection, accumulation and caring) within agroecological systems that focus on individual plants, rather than populations—as is typical of agriculture. The early archaeobotanical record includes numerous perennial and annual species, many of which later became domesticated. Some of this evidence identifies dispersal with probable cultivation, suggesting incipient domestication by 10,000 years ago. Since the Pleistocene, more than 6500, 1206 and 6261 native plant species have been used in Mesoamerica, the Central Andes and lowland South America, respectively. At least 1555, 428 and 742 are managed outside and inside food production systems, and at least 1148, 428 and 600 are cultivated, respectively, suggesting at least incipient domestication. Full native domesticates are more numerous in Mesoamerica (251) than the Andes (124) and the lowlands (45). This synthesis reveals that domestication is more common in the Neotropics than previously recognized and started much earlier than reliance on food production systems. Hundreds of ethnic groups had, and some still have, alternative strategies that do involve domestication, although they do not rely principally on food production systems, such as agriculture.

Native Amazonian populations managed forest resources in numerous ways, often creating oligarchic forests dominated by useful trees. The scale and spatial distribution of forest modification beyond pre-Columbian settlements is still unknown, although recent studies propose that human impact away from rivers was minimal. We tested the hypothesis that past human management of the useful tree community decreases with distance from rivers. In six sites, we inventoried trees and palms with DBH≥10 cm and collected soil for charcoal analysis; we also mapped archaeological evidence around the sites. To quantify forest manipulation, we measured the relative abundance, richness and basal area of useful trees and palms. We found a strong negative exponential relationship between forest manipulation and distance to large rivers. Plots located from 10 to 20 km from a main river had 20-40% useful arboreal species, plots between 20 and 40 km had 12-23%, plots more than 40 km had less than 15%. Soil charcoal abundance was high in the two sites closest to secondary rivers, suggesting past agricultural practices. The shortest distance between archaeological evidence and plots was found in sites near rivers. These results strongly suggest that past forest manipulation was not limited to the pre-Columbian settlements along major rivers, but extended over interfluvial areas considered to be primary forest today. The sustainable use of Amazonian forests will be most effective if it considers the degree of past landscape domestication, as human-modified landscapes concentrate useful plants for human sustainable use and management today.