miércoles, 30 de septiembre de 2020

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THE MAN BORN TO FARMING
By Wendell Berry

The grower of trees, the gardener, the man born to farming, whose hands reach into the ground and sprout, to him the soil is a divine drug. He enters into death yearly, and comes back rejoicing. He has seen the light lie down in the dung heap, and rise again in the corn.
His thought passes along the row ends like a mole.
What miraculous seed has he swallowed that the unending sentence of his love flows out of his mouth like a vine clinging in the sunlight, and like water descending in the dark? 
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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.

https://bit.ly/361Nqdi

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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. 

https://bit.ly/3hZTx43

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martes, 22 de septiembre de 2020

Complejidad ecológica y control biológico autónomo de plagas
John Vandermeer e Ivette Perfecto.

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


sábado, 12 de septiembre de 2020

Resistance-genes affect how pathogens maintain plant abundance and diversity
Stump et al., 2020

Specialized pathogens are thought to maintain plant community diversity; however, most ecological studies treat pathogens as a black-box. Here we develop a theoretical model to test how the impact of specialized pathogens changes when plant resistance (R) genes mediate susceptibility. This work synthesizes two major hypotheses: the gene-for-gene model of pathogen resistance and the Janzen-Connell hypothesis of pathogen-mediated coexistence. We examine three scenarios. First, R-genes do not affect seedling survival; in this case, pathogens promote diversity. Second, seedlings are protected from pathogens when their R-gene alleles and susceptibility differ from those of nearby conspecific adults, thereby reducing transmission. If resistance is not costly, pathogens are less able to promote diversity because populations with low R-gene diversity suffer higher mortality, putting those populations at a disadvantage, and potentially causing their exclusion. R-gene diversity may also be reduced during population bottlenecks, creating a priority effect. Third, when R-genes affect survival, but resistance is costly, populations can avoid extinction by losing resistance alleles, as they cease paying a cost that is unneeded. Thus, the impact pathogens can have on tree diversity depends on the mechanism of plant-pathogen interactions. Future empirical studies should examine which of these scenarios most closely reflects the real world. 

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jueves, 10 de septiembre de 2020

Conditioning the soil microbiome through plant–soil feedbacks suppresses an aboveground insect pest 
Pineda et al., 2019

  • 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.


Community structure for bacteria (a) and fungi (b) in the inocula and in the inoculated soils after chrysanthemum growth, colored by plant species (sterilized control in black) in Expt 1. Centroids are shown as large dots and lines connecting the individual samples to the centroids. Inocula were conditioned by grasses (AP, Alopecurus pratensis; FO, Festuca ovina; HL, Holcus lanatus; LP, Lolium perenne) or forbs (AM, Achillea millefolium; GM, Galium mollugo; RA, Rumex acetosella; TM, Tripleurospermum maritimum).  

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domingo, 6 de septiembre de 2020

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The Death of the Moth
By Virginia Woolf

Moths that fly by day are not properly to be called moths; they do not excite that pleasant sense of dark autumn nights and ivy-blossom which the commonest yellow-underwing asleep in the shadow of the curtain never fails to rouse in us. They are hybrid creatures, neither gay like butterflies nor sombre like their own species. Nevertheless the present specimen, with his narrow hay-coloured wings, fringed with a tassel of the same colour, seemed to be content with life. It was a pleasant morning, mid-September, mild, benignant, yet with a keener breath than that of the summer months. The plough was already scoring the field opposite the window, and where the share had been, the earth was pressed flat and gleamed with moisture. Such vigour came rolling in from the fields and the down beyond that it was difficult to keep the eyes strictly turned upon the book. The rooks too were keeping one of their annual festivities; soaring round the tree tops until it looked as if a vast net with thousands of black knots in it had been cast up into the air; which, after a few moments sank slowly down upon the trees until every twig seemed to have a knot at the end of it. Then, suddenly, the net would be thrown into the air again in a wider circle this time, with the utmost clamour and vociferation, as though to be thrown into the air and settle slowly down upon the tree tops were a tremendously exciting experience.

The same energy which inspired the rooks, the ploughmen, the horses, and even, it seemed, the lean bare-backed downs, sent the moth fluttering from side to side of his square of the window-pane. One could not help watching him. One was, indeed, conscious of a queer feeling of pity for him. The possibilities of pleasure seemed that morning so enormous and so various that to have only a moth's part in life, and a day moth's at that, appeared a hard fate, and his zest in enjoying his meagre opportunities to the full, pathetic. He flew vigorously to one corner of his compartment, and, after waiting there a second, flew across to the other. What remained for him but to fly to a third corner and then to a fourth? That was all he could do, in spite of the size of the downs, the width of the sky, the far-off smoke of houses, and the romantic voice, now and then, of a steamer out at sea. What he could do he did. Watching him, it seemed as if a fibre, very thin but pure, of the enormous energy of the world had been thrust into his frail and diminutive body. As often as he crossed the pane, I could fancy that a thread of vital light became visible. He was little or nothing but life.

Yet, because he was so small, and so simple a form of the energy that was rolling in at the open window and driving its way through so many narrow and intricate corridors in my own brain and in those of other human beings, there was something marvellous as well as pathetic about him. It was as if someone had taken a tiny bead of pure life and decking it as lightly as possible with down and feathers, had set it dancing and zig-zagging to show us the true nature of life. Thus displayed one could not get over the strangeness of it. One is apt to forget all about life, seeing it humped and bossed and garnished and cumbered so that it has to move with the greatest circumspection and dignity. Again, the thought of all that life might have been had he been born in any other shape caused one to view his simple activities with a kind of pity.

After a time, tired by his dancing apparently, he settled on the window ledge in the sun, and, the queer spectacle being at an end, I forgot about him. Then, looking up, my eye was caught by him. He was trying to resume his dancing, but seemed either so stiff or so awkward that he could only flutter to the bottom of the window-pane; and when he tried to fly across it he failed. Being intent on other matters I watched these futile attempts for a time without thinking, unconsciously waiting for him to resume his flight, as one waits for a machine, that has stopped momentarily, to start again without considering the reason of its failure. After perhaps a seventh attempt he slipped from the wooden ledge and fell, fluttering his wings, on to his back on the window sill. The helplessness of his attitude roused me. It flashed upon me that he was in difficulties; he could no longer raise himself; his legs struggled vainly. But, as I stretched out a pencil, meaning to help him to right himself, it came over me that the failure and awkwardness were the approach of death. I laid the pencil down again.

The legs agitated themselves once more. I looked as if for the enemy against which he struggled. I looked out of doors. What had happened there? Presumably it was midday, and work in the fields had stopped. Stillness and quiet had replaced the previous animation. The birds had taken themselves off to feed in the brooks. The horses stood still. Yet the power was there all the same, massed outside indifferent, impersonal, not attending to anything in particular. Somehow it was opposed to the little hay-coloured moth. It was useless to try to do anything. One could only watch the extraordinary efforts made by those tiny legs against an oncoming doom which could, had it chosen, have submerged an entire city, not merely a city, but masses of human beings; nothing, I knew, had any chance against death. Nevertheless after a pause of exhaustion the legs fluttered again. It was superb this last protest, and so frantic that he succeeded at last in righting himself. One's sympathies, of course, were all on the side of life. Also, when there was nobody to care or to know, this gigantic effort on the part of an insignificant little moth, against a power of such magnitude, to retain what no one else valued or desired to keep, moved one strangely. Again, somehow, one saw life, a pure bead. I lifted the pencil again, useless though I knew it to be. But even as I did so, the unmistakable tokens of death showed themselves. The body relaxed, and instantly grew stiff. The struggle was over. The insignificant little creature now knew death. As I looked at the dead moth, this minute wayside triumph of so great a force over so mean an antagonist filled me with wonder. Just as life had been strange a few minutes before, so death was now as strange. The moth having righted himself now lay most decently and uncomplainingly composed. O yes, he seemed to say, death is stronger than I am.
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viernes, 4 de septiembre de 2020

The effectiveness of flower strips and hedgerows on pest control, pollination services and crop yield: a quantitative synthesis
Albrechtet al., 2020


Floral plantings are promoted to foster ecological intensification of agriculture through provisioning of ecosystem services. However, a comprehensive assessment of the effectiveness of different floral plantings, their characteristics and consequences for crop yield is lacking. Here we quantified the impacts of flower strips and hedgerows on pest control (18 studies) and pollination services (17 studies) in adjacent crops in North America, Europe and New Zealand. Flower strips, but not hedgerows, enhanced pest control services in adjacent fields by 16% on average. However, effects on crop pollination and yield were more variable. Our synthesis identifies several important drivers of variability in effectiveness of plantings: pollination services declined exponentially with distance from plantings, and perennial and older flower strips with higher flowering plant diversity enhanced pollination more effectively. These findings provide promising pathways to optimise floral plantings to more effectively contribute to ecosystem service delivery and ecological intensification of agriculture in the future.


Forest plot showing effects of flower strips and hedgerows on pollination and pest control service provisioning in adjacent crops compared to control crops without adjacent floral plantings. Squares illustrate predicted mean effects (z‐score estimates), bars show 95% confidence intervals (CIs). On average, pest control services were enhanced by 16% (z‐score: 0.25) in fields with adjacent flower strip compared to control fields.  


Predicted relationships between (a) mean natural pest control service and (b) mean crop pollination service (z‐scores (solid lines) ± 95% CI (dashed lines)) and in‐field distance to field border for field with (red lines; dots) or without adjacent floral planting (black lines, triangles). 

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