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Simplicissimus @simplicissimus 14/05/2016

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Florida sinkhole archeological site recasts ’peopling of the Americas’ narrative - CSMonitor.com
▻http://www.csmonitor.com/Science/2016/0513/Florida-sinkhole-archeological-site-recasts-peopling-of-the-Americas-narr
Deep in an underwater sinkhole in a river in Florida, archeologists have found the remains of a prehistoric population of humans that lived in the region some 14,550 years ago. Stone tools, mastodon bones with distinct cut marks, and mastodon dung hold enticing clues into the lives of these early Americans and the megafauna around them. Those new findings are reported in a paper published Friday in the journal Science Advances.
Today these findings are accepted as adding to the early prehistory of the Americas, but that wasn’t the case for artifacts unearthed from the same site just decades ago.

Simplicissimus @simplicissimus
- Simplicissimus @simplicissimus 14/05/2016
  
  Pre-Clovis occupation 14,550 years ago at the Page-Ladson site, Florida, and the peopling of the Americas | Science Advances
  ▻http://advances.sciencemag.org/content/2/5/e1600375
  Abstract
  Stone tools and mastodon bones occur in an undisturbed geological context at the Page-Ladson site, Florida. Seventy-one radiocarbon ages show that ~14,550 calendar years ago (cal yr B.P.), people butchered or scavenged a mastodon next to a pond in a bedrock sinkhole within the Aucilla River. This occupation surface was buried by ~4 m of sediment during the late Pleistocene marine transgression, which also left the site submerged. Sporormiella and other proxy evidence from the sediments indicate that hunter-gatherers along the Gulf Coastal Plain coexisted with and utilized megafauna for ~2000 years before these animals became extinct at ~12,600 cal yr B.P. Page-Ladson expands our understanding of the earliest colonizers of the Americas and human-megafauna interaction before extinction.
  http://d3a5ak6v9sb99l.cloudfront.net/content/advances/2/5/e1600375/F2.large.jpg
  
  Fig. 2 Stratigraphy of excavation units at the Page-Ladson site displaying pre-Clovis artifacts and radiocarbon ages.
  (A) Artifact 12209-a. (B) Artifact 12209-b. (C) Artifact 12242-1. (D) Artifact 12068-2. (E) Artifact 12068-1. (F) Artifact 12080-1. (A) to (E) are flakes; (D) shows evidence of use. (F) is a biface. (G) 2014 wall profiles showing stratigraphy, locations of artifact finds, and location of radiocarbon samples. (H) 2013 wall profiles showing stratigraphy, locations of artifact finds, and location of radiocarbon samples. For (G) and (H), white dots represent locations and ages of radiocarbon samples collected from profiles. Purple dots and text represent radiocarbon ages collected from within units, plotted with correct elevation, and northing or easting. Red triangles show locations of artifacts collected from within units, plotted with correct elevation, and northing or easting. Open red circle shows approximate location of artifacts found in the screen. Trees in the profile are represented by dark brown. Note that although the biface appears as if it were found in the middle of a tree, the tree only occurs in the south wall profile and does not extend into the excavation unit where the biface was found.
  
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Lyco @lyco 30/05/2015

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Saigas, an Endangered Antelope, Dying of Mystery Disease
▻http://www.nytimes.com/2015/06/02/science/saiga-antelope-mystery-disease-die-off.html

http://static01.nyt.com/images/2015/05/30/science/02antelope-a/02antelope-a-master675.jpg

In the past two weeks, more than third of all saigas have been killed, conservationists have found.
[...]
“To lose 120,000 animals in two or three weeks is a phenomenal thing.”
[...]
The scientists found that the animals were infected with two species of deadly bacteria, Pasteurella and Clostridium. But Dr. Kock is convinced that the bacteria are not the fundamental cause of the die-off.
Both species of bacteria are present in healthy animals, becoming lethal only when the animals grow weak. Dr. Kock also observed that the saiga died so quickly from their infections that they could not have spread the bacteria to other animals.
“The time period is too short,” he said.
Dr. Kock and his colleagues are investigating other factors that may have triggered the die-off, including the possibility of an unknown virus. Dr. Kock said it will take three or four weeks to isolate any agent in the necropsy tissues.
The scientists are also looking at how changes in the environment may have put stress on the saiga. Heavy rainfall this year may have altered the ecology of the steppes, disrupting their food supply, for example.
[...]
“The die-off may not be over,” she said. “This is unconfirmed, but it fills us with great fear.”
#extinction #saïgas #biodiversité

Lyco @lyco
- Lyco @lyco 15/08/2015
  
  He said that according to preliminary results, the cause of death of saiga is hemorrhagic septicemia. It is an infection that involves bacteria producing many different toxins. The researchers suspect that the pathogens were spread by ticks that populate the steppes in great numbers in late April-early May.
  ▻http://en.tengrinews.kz/environment/Foreign-experts-present-findings-on-mass-saiga-pestilence-in-261483
  
  Lyco @lyco
- Lyco @lyco 24/09/2015
  
  Début septembre, des chercheurs rapportent que 60.000 de ces antilopes asiatiques sont tombées les unes à la suite des autres, sans raison, en l’espace de seulement 4 jours.
  ▻http://www.sciencesetavenir.fr/animaux/20150907.OBS5383/60-000-antilopes-decedent-mysterieusement-au-kazahkstan.html
  
  Lyco @lyco
- Lyco @lyco 3/11/2015
  
  At a scientific meeting last week in Tashkent, Uzbekistan, Dr. Kock and his colleagues reported that they had narrowed down the possible culprits. #Climate change and stormy spring weather, they said, may have transformed harmless bacteria carried by the antelopes, called saigas, into lethal pathogens.
  It is a scenario that deeply worries scientists. “It’s not going to be something the species can survive,” Dr. Kock said. “If there are weather triggers that are broad enough, you could actually have extinction in one year.”
  ▻http://www.nytimes.com/2015/11/03/science/more-than-half-entire-species-of-saigas-gone-in-mysterious-die-off.html
  
  Lyco @lyco
- Lyco @lyco 18/06/2016
  
  After mass die-off, saiga antelope numbers go up in Kazakhstan
  ▻https://news.mongabay.com/2016/06/after-mass-die-off-saiga-antelope-numbers-go-up-in-kazakhstan
  A recent aerial survey of saigas carried out from April 18 to May 3, 2016 has revealed that the numbers of all three saiga populations in Kazakhstan—Ural, Betpak-Dala and Ustyurt — are going up. [...] The surveys counted a total of 108,300 adult saigas. The Ural population has about 70,200 individuals, up from 51,700 in 2015, while the Ustyurt population has around 1,900 individuals, up from 1,200 in 2015. The Betpak-Dala population also showed promise with about 36,200 individuals, the results revealed.
  [...] “This is far below the 242,000 animals we counted in spring 2015, before the mass-die off,” Albert Salemgareyev from ACBK, co-leader of the Altyn Dala Conservation Initiative, said. “But we are grateful for this glimpse of hope.”
  [...] Scientists are continuing to investigate the conditions that could have led to the 2015 mass deaths.
  
  Lyco @lyco
- Lyco @lyco 10/04/2018
  
  Saigas on the brink: Multidisciplinary analysis of the factors influencing mass mortality events (Kock et al., 2018)
  ▻http://advances.sciencemag.org/content/4/1/eaao2314.full
  
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CNRS - Le Journal (RSS) @cnrs 8/04/2015

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Forêts morcelées, oiseaux menacés ?
▻https://lejournal.cnrs.fr/diaporamas/forets-morcelees-oiseaux-menaces
À cause des constructions humaines, la forêt guyanaise est de plus en plus fragmentée, c’est-à-dire découpée en parcelles de plus en plus petites et isolées. Quel en est l’impact sur la biodiversité, et plus précisément sur les oiseaux ? Des chercheurs français mènent l’enquête dans les forêts du littoral, particulièrement touchées par ce phénomène, afin d’influencer les politiques locales.
- #Amazon
CNRS - Le Journal (RSS) @cnrs
- odilon @odilon CC BY-NC-ND 8/04/2015
  
  #forêt #écologie #biodiversité
  
  odilon @odilon CC BY-NC-ND
- Lyco @lyco 9/04/2015
  
  Habitat fragmentation and its lasting impact on Earth’s ecosystems
  ▻http://advances.sciencemag.org/content/1/2/e1500052
  This analysis revealed that nearly 20% of the world’s remaining forest is within 100 m of an edge (Fig. 1, A and B)—in close proximity to agricultural, urban, or other modified environments where impacts on forest ecosystems are most severe (14). More than 70% of the world’s forests are within 1 km of a forest edge. Thus, most forests are well within the range where human activities, altered microclimate, and nonforest species may influence and degrade forest ecosystems (15). The largest contiguous expanses of remaining forests are in the humid tropical regions of the Amazon and Congo River Basins
  
  Lyco @lyco
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