ARVE Research Group – University of Lausanne

The interdisciplinary ARVE team studies the interaction between soils, vegetation and the atmosphere.

[arvegroup-blog]

Newly available : Human subsistence and land use in sub-Saharan Africa

Our latest publication is now freely available (for 3 months) at  http://www.sciencedirect.com/science/article/pii/S2213305415000302 'Human subsistence and land use in sub-Saharan Africa, 1000 BC to AD 1500: A review, quantification, and classification' from authors Andrea Kay and Jed Kaplan.

Learn more about the authors Jed O. Kaplan and Andrea U. Kay on our website: http://arve.unil.ch/people/

Abstract The Iron Age transition in sub-Saharan Africa represents a time when the relationship between humans and their environment was fundamentally altered at near-continental scale. This alteration may have had widespread consequences for regional climate, hydrology, biodiversity and ecosystem services that persist to the present. Quantification of these impacts and potential feedbacks is difficult, however, because the archaeological and historical record is highly fragmented in time and space. Here, we present a classification of human subsistence in Iron Age Africa from 1000 BC to AD 1500 that illustrates the various degrees of land use intensity employed by different groups at different times. The classification is based on a broad synthesis of archaeological, archaeobotanical, and ethnographic observations. The primary goal of our classification is to employ it as input to quantitative models of human–environment interactions to test hypotheses on the importance of humans for the development of African environments over the late Holocene.

[scinote]

How Have Volcanoes Shaped Our Climate?

The more we understand the history of Earth’s climate, the better we understand the complexities of its future.  A massive collaboration involving scientists from around the world, led by the Desert Research Institute in Nevada, has helped show the impact volcanoes have had on the climate. When a volcano erupts, it spews tons of material into the air, which gets into the atmosphere and blocks some of the Sun’s radiation, causing a cooling effect. One example of this was in 1991, when Mt. Pinatubo in the Philippines erupted. The eruption caused a cooling of 0.5 ᵒC in the North Hemisphere. This kind of cooling can have massive consequences in predicting climate change, so a greater understanding of the effect is incredibly important. We are able to gain this understanding by analyzing our environment. The sulfur that volcanoes eject will always eventually land on Earth; this is taken up by trees and can be seen in tree rings. It also lands on ice and is incorporated into the ice sheets. Scientists drill into the ice and extract long cylinders of ice called ice cores, which are so sensitive to change that a drop in lead can be seen in when unleaded petrol became the norm. It can be hard to accurately pin records from ice cores to records from tree rings, as it’s often done by simply judging that a change of sulfur in both the ice and the trees were from the same event. Using different timescales from each can often make things inaccurate. Recently, sudden changes in an isotope of carbon, carbon-14, have been found in tree rings very soon after volcanic eruptions. We’ve been able to accurately date this using an eruption from 775 AD, and using multiple trees from all over the Northern Hemisphere. The scientists in this new study assumed that a radioactive isotope of beryllium, beryllium-10, would also be created in greater quantities during an eruption, because this isotope is made when cosmic rays interact with particles in the atmosphere. This gives us a way to pin tree data to ice core data, using independent but simultaneous events. Using this information, scientists went back through previous records of ice cores and found them to be inaccurate. Some eruptions in Greenland were found to be seven years out of line with the tree ring data. This data allowed the scientists to create a new model spanning the last 2,500 years. The model shows hundreds of eruptions that influenced the climate, and shows that tropical eruptions were the cause of numerous cooling events. It has been found that between 500 BC and 1000 AD, 15 of the 16 coldest summers were after tropical eruptions. They were also able to solve a mystery: there were a number of strange cooling occurrences in the early part of the sixth century. A dust cloud was observed in records in 536 AD; this was thought to have been due to an eruption, but was never proven. The new paper shows that it must have been caused by at least two tropical eruptions. This new understanding of previous events will greatly help our planning for future change. Sources Link to article: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature14565.html Study on carbon 14 in tree rings: http://www.nature.com/nature/journal/v486/n7402/full/nature11123.html Mt. Pinatubo data: http://pubs.usgs.gov/pinatubo/self/ Lead in ice cores: http://www.sciencewa.net.au/topics/environment-a-conservation/item/1271-mt-everest-ice-core-reveals-atmospheric-lead-history/1271-mt-everest-ice-core-reveals-atmospheric-lead-history More info on paleoclimatology: http://serc.carleton.edu/microbelife/topics/proxies/paleoclimate.html By Adam M., Discoverer. Edited by Anna G.

[arvegroup-blog]

Generate climate diagrams for all parts of the world courtesy of Jed Kaplan and colleagues, http://arve.unil.ch/climap  Visit, and leave us your comments!

[geoscienceimpacts]

Instrumental climate data only extend back to the mid-19th century, at best, which means that the anthropogenic climate change signals we are chasing are in most cases longer than the available climate records. A wealth of climate history can be extracted from geologic archives such as corals,...

[msci-browsings-by-drhardee]

So, if you’re a paleoclimate science geek like me and follow climate change, and read / study / breathe paleoclimate-related anything, you know that the longest ice core recovered to date extends back to nearly 800,000 years, recovered from Dome C in Antarctica by the European’s EPICA Project back in 2004 (see here for the 2004 news article: http://www.scientificamerican.com/article.cfm?id=record-breaking-ice-core, and European Science Foundation's slightly scientific-writing but great explanation of the EPICA site’s history and discoveries.)  It was a big, BIG deal, hyoouge, when that happened (still is), as it gave us climate resolution across eight glacial-interglacial cycles at a temporal resolution of ~1000 years or so (pretty darn high resolution for hundreds of thousands of years of ice compacted under miles of even more ice, yes?).  Now, U.S. scientists have recovered an ice core that is only a paltry 68,000 years ‘long’ in age.  “Yawn”, you say?  How about if I then tell you, that this core’s temporal resolution is … ANNUAL.  Yeah, annual, as in, yearly bands of ice that can be counted, yeah, COUNTED (!) back more than 30,000 years.  And measured for oxygen and deuterium isotopes, dust, CO2, all those fun-climate-chemistry-toys.  Heck, this level of resolution is difficult to find in the present day ocean sediments, much less the 60,000 years through the past!  

Drilling for ice core climate records in Antarctica (image source:  http://www.thenakedscientists.com/HTML/content/interviews/interview/643/)

An ice core (this one happens to be from Greenland’s GISP2 site).  Image source: http://www.globalwarmingart.com/wiki/File:GISP2_Ice_Core_jpg. 

Ancient air bubbles get trapped in ice when the ice gets buried and compacted.  These bubbles can be measured with sensitive equipment for CO2 and methane concentrations that were present in that ancient atmosphere, as well as measurements of oxygen and deuterium isotopes in the ice itself (which can tell you air and ocean temperatures, evaporation, precipitation, and other cool climate stuff - see the EPICA project page above for an explanation).

[arvegroup-blog]

The interdisciplinary ARVE team studies the interaction between soils, vegetation and the atmosphere. Our current research focuses on how human activities have modified the terrestrial biosphere over the Holocene and how these changes in vegetation could have altered atmospheric chemistry and climate. We study human-environment interactions at large spatial and temporal scales using vegetation and… Read More »

Come visit our main web website, for information about our projects, activities, members, and more.

[arvegroup-blog]

New publication from ARVE Research Group : We are quantifying and classifying past land use in sub-Saharan Africa. How did these activities impact land cover?

[arvegroup-blog]

Soil Erosion in Mesoamerica showing how high rates of soil erosion are associated with humid, steep terrain, and human impact from 8000 BP to 0 BP.

[arvegroup-blog]

NATURE published work in 2012 involving ARVE researchers Prof. Jed Kaplan and Kristen Krumhardt : 'Natural and anthropogenic variations in methane sources during the past two millennia'.