miércoles, 30 de septiembre de 2020
domingo, 27 de septiembre de 2020
The origins of Amazonian landscapes: Plant cultivation, domestication and the spread of food production in tropical South America
Iriarte et al., 2020
Amazonian plant domestication is unique, differs from Eurasian processes, and needs to be study in ‘its own terms’.
Earliest colonists relied on palms, tree fruits, and underground tubers, along with terrestrial and riverine fauna.
Two areas of precocious plant domestication: sub-Andean montane forests (NW) and the shrub savannahs (SW).
First direct evidence of field polyculture agriculture within closed-canopy agroforestry and low-severity fire management.
Late Holocene spread of Amazonian anthrosols and investment in landesque capital is followed by population growth.
During the last two decades, new archaeological projects which systematically integrate a variety of plant recovery techniques, along with palaeoecology, palaeoclimate, soil science and floristic inventories, have started to transform our understanding of plant exploitation, cultivation and domestication in tropical South America. Archaeobotanical studies are providing a far greater appreciation of the role of plants in the diets of early colonists. Since ∼13ka, these diets relied mainly on palm, tree fruits, and underground tubers, along with terrestrial and riverine faunal resources. Recent evidence indicates two areas of precocious plant cultivation and domestication: the sub-Andean montane forest of NW South America and the shrub savannahs and seasonal forests of SW Amazonia. In the latter area, thousands of anthropic keystone structures represented by forest islands show a significant human footprint in Amazonia from the start of the Holocene. While radiocarbon date databases show a decline in population during the middle Holocene, important developments happened during this epoch, including the domestication of cacao, the adoption of maize and the spread of manioc across the basin. The late Holocene witnessed the domestication of rice and the development of agricultural landscapes characterised by raised fields and Amazonian Dark Earths (ADEs). Our multi-proxy analysis of 23 late Holocene ADEs and two lakes from southern Amazonia provides the first direct evidence of field polyculture agriculture including the cultivation of maize, manioc, sweet potato, squash, arrowroot and leren within closed-canopy forest, as well as enrichment with palms, limited clearing for crop cultivation, and low-severity fire management. Collectively, the evidence shows that during the late Holocene Amazonian farmers engaged in intensive agriculture marked by the cultivation of both annual and perennial crops relying on organic amendments requiring soil preparation and maintenance. Our study has broader implications for sustainable Amazonian futures.
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viernes, 25 de septiembre de 2020
jueves, 24 de septiembre de 2020
Is biodiversity bad for your health?
Richard S. Ostfeld Felicia Keesing, 2017
Natural ecosystems provide services that support human well‐being, but ecosystems may also contain elements that can endanger humans. Some researchers have argued that ecosystems that support high vertebrate diversity pose a danger to human health because they are likely to support a high diversity of zoonotic pathogens, leading to the emergence of infectious diseases. We evaluated the evidence for the three necessary links in the hypothesized causal chain linking high vertebrate diversity to a high probability of emergence of infectious diseases. We found no support for one critical link—that high total diversity of vertebrate pathogens correlates with high diversity of actual or potential zoonotic pathogens. In contrast, there is now substantial evidence that high diversity protects humans against the transmission of many existing diseases. These results have substantial relevance for environmental policy.
The necessary logical steps underlying the argument that high host diversity leads to high probability of the emergence of a zoonotic disease. High diversity of vertebrate hosts must result in high total diversity of pathogens within the vertebrate community, which in turn must lead to high diversity of actual or potential zoonotic pathogens (those that can infect humans and cause disease), which in turn must increase the probability of new emergence events. Although a link between host diversity and parasite diversity is relatively well established, effect of host diversity on viral and bacterial pathogens (arrow 1) is not. Evidence does not support a link between overall pathogen diversity and that of actual or potential zoonotic pathogens (arrow 2). Some evidence supports correlations between diversity of zoonotic pathogens and the likelihood of zoonotic emergence (arrow 3), but with important caveats described in the text.
Schematic diagram of how parasite diversity is expected to vary with host diversity when parasites show high host specificity (upper curve) and when they show low host specificity (lower curve). In the latter case, the sharing of parasites between hosts means that the diversity of parasites will saturate as host diversity increases, resulting in little or no additional increases in parasite species at high levels of host diversity.
Schematic representation of typical rank–abundance curves, in which the relative abundance of each species is represented on the vertical axis and the rank of each species, from highest to lowest abundance, is given on the horizontal axis. Contrasted are two scenarios, a relatively low‐diversity community in blue and a relatively high‐diversity community in green. The curves represent the common observation that higher‐diversity communities include more species that are rare and fewer that are common. The species added (right‐hand orange circle) in higher‐diversity communities are not likely to be the sources of zoonotic pathogens, whereas the most abundant species in lower‐diversity communities (left‐hand orange circle) are often the sources of zoonotic infection.
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martes, 22 de septiembre de 2020
John Vandermeer e Ivette Perfecto.
domingo, 20 de septiembre de 2020
sábado, 19 de septiembre de 2020
Bending the curve of terrestrial biodiversity needs an integrated strategy
Leclère et al., 2020
Increased efforts are required to prevent further losses to terrestrial biodiversity and the ecosystem services that it provides. Ambitious targets have been proposed, such as reversing the declining trends in biodiversity; however, just feeding the growing human population will make this a challenge. Here we use an ensemble of land-use and biodiversity models to assess whether—and how—humanity can reverse the declines in terrestrial biodiversity caused by habitat conversion, which is a major threat to biodiversity. We show that immediate efforts, consistent with the broader sustainability agenda but of unprecedented ambition and coordination, could enable the provision of food for the growing human population while reversing the global terrestrial biodiversity trends caused by habitat conversion. If we decide to increase the extent of land under conservation management, restore degraded land and generalize landscape-level conservation planning, biodiversity trends from habitat conversion could become positive by the mid-twenty-first century on average across models (confidence interval, 2042–2061), but this was not the case for all models. Food prices could increase and, on average across models, almost half (confidence interval, 34–50%) of the future biodiversity losses could not be avoided. However, additionally tackling the drivers of land-use change could avoid conflict with affordable food provision and reduces the environmental effects of the food-provision system. Through further sustainable intensification and trade, reduced food waste and more plant-based human diets, more than two thirds of future biodiversity losses are avoided and the biodiversity trends from habitat conversion are reversed by 2050 for almost all of the models. Although limiting further loss will remain challenging in several biodiversity-rich regions, and other threats—such as climate change—must be addressed to truly reverse the declines in biodiversity, our results show that ambitious conservation efforts and food system transformation are central to an effective post-2020 biodiversity strategy.
https://www.nature.com/articles/s41586-020-2705-y
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miércoles, 16 de septiembre de 2020
lunes, 14 de septiembre de 2020
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¿Y si al final no se puede sondear la naturaleza?
Goethe
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sábado, 12 de septiembre de 2020
Stump et al., 2020
jueves, 10 de septiembre de 2020
- Soils and their microbiomes are now recognized as key components of plant health, but how to steer those microbiomes to obtain their beneficial functions is still unknown. Here, we assess whether plant–soil feedbacks can be applied in a crop system to shape soil microbiomes that suppress herbivorous insects in above‐ground tissues.
- We used four grass and four forb species to condition living soil. Then we inoculated those soil microbiomes into sterilized soil and grew chrysanthemum as a focal plant. We evaluated the soil microbiome in the inocula and after chrysanthemum growth, as well as plant and herbivore parameters.
- We show that inocula and inoculated soil in which a focal plant had grown harbor remarkably different microbiomes, with the focal plant exerting a strong negative effect on fungi, especially arbuscular mycorrhizal fungi. Soil inoculation consistently induced resistance against the thrips Frankliniella occidentalis, but not against the mite Tetranychus urticae, when compared with sterilized soil. Additionally, plant species shaped distinct microbiomes that had different effects on thrips, chlorogenic acid concentrations in leaves and plant growth.
- This study provides a proof‐of‐concept that the plant–soil feedback concept can be applied to steer soil microbiomes with the goal of inducing resistance above ground against herbivorous insects.
domingo, 6 de septiembre de 2020
viernes, 4 de septiembre de 2020
Albrechtet al., 2020