* Sampling biases exist in our datasets, which become apparent as we collect more data (this is exactly what my poster next month at EGU is about!).
* Review paper: there are 3 in the last few years (4 from 2002) which make use of much of the same data but come to different conclusion. People are sneaky and use the evidence that best fits their hypotheses…
* Don’t forget the errors associated with dates. The suggested phases without errors from primary papers get regurgitated in review papers and somehow become fact… (see chapter 10 of my thesis for this rant also!)
* Histograms of age frequencies from records across the Kalahari are sampling site bias! and might be meaningless!
* With OSL dates 5% errors are the best we can get
* Advocated the use of a presence or absence of ages in 1 ka bin widths as an alternative to the histogram. (one problem is losing the error information).
Read this paper in QI when it is published!(3) Groundwater age and renewability in NW China
Professor Mike Edmunds brought us closer to the modern day for the first time at the meeting, presenting work on groundwater recharge rate assessment in China (co authors John Gates, now in the US and Li Ma, postdoc in Oxford). He posed one simple question – “is the water in deserts, and beneathe deserts, part of the active hydrological cycle or part of a past hydrological cycle?” This has huge impacts for society and resourcse sustainability and renewability, or not!
These approaches use chloride as a tracer and mass balance approaches to calculate rates of most mmodern recharge. Mike showed us results from the Minqin Basin and the Badain Jaran desert (see the papers by John Gates in NW China and also result from northern Africa). The difficult message from this research is that groundwater, on which the populations of these arid areas rely, are not renewable, being used far more quickly than they recharge. This calls for new approaches in management and education.
(4) Livelihood sustainability in drylands
Andy Dougill, head of the School of Earth and Environment at Leeds University then spoke to us about sustainability of livelihoods. He highlighted that he has details of 7 case studies available for those who would like to see examples of these ideas, and that these will appear in an special issue of Ecology and Society. His focus is on the local scale – how livelihood systems in drylands are affected by drought, and a call for a critical reflection on integrated modelling approaches. The tag line is ‘closing loops’.
(5) Rejecting authenticity in the desert landscapes of the modern MIddle East (Oman)
Dawn Chatty from the Refugee Studies Centre, University of Oxford, kept us in the realm of modern human environments in deserts, looking at the interaction between human populations and the environments in Oman, middle East and the role of different scales of policy management, from the head of state, through middle management to the tribal people. Dawn brought us a great deal of knowledge spanning work with the UN from the 1980s to the present day.
(1) Dust in the Sahara
Richard Washington from this host department took us back to Africa after lunch with his presentation about dust in the Sahara, reporting on the work completed in the Bodele Depression and his plans for forthcoming work in the western Sahara.
With respect to the Bodele work he answered three important questions:
1) why does this region produce so much dust? – Bodele is located in the ‘bulls eye’ of windspeed over a depression (the Bodele Low Level Jet) (see Washington and Todd, 2005)
2) what can we learn from the past? – The depression has filled with water a number of times during the past 18 ka, and deposited the diatomite sediment that is now easily deflated. E.g.
(Washington et al., 2006). Topography is also very important. Removing topography from the model, wind speed reduces by 30 %.
3) what is predicted for the future? The Bodele Low Level Jet is predicted to get bigger in the future… have a look at Washington et al. (2009).
Richard also set out his plans for the forthcoming field campagin to investigate dust loadings in the west Sahara (FENNEC).
(2) Climate change and cultural transitions over the last 160,000 years in NW Africa.
Angela Vaughan, kept us in northern Africa, looking at the record preserved in the Grotte des Pigeons at Taforalt in Morocco. This cave is an important one, as it contains one of the longest, and potentially continuous sequences of environmental and archaeological change. Angela talked us through a number of the sectors of the cave. At sector 2, layer 14 (dated to 45-50 ka) suggests the Alterian was longer lived than generally perceived. There is a halt in evidence around 25 ka, suggesting a break in the occupation of the cave, over which LGM layers are found. Above this different lithics are from the iberomaurusian. An intensification of the use of the cave is indicated from 13-11 ka, with evidence for modern behavioural traits, such as burial practices. This culture also practiced the removal of the two front teeth. Angela will continue to reconstruct the local environmental conditions at this site and link these to marine record (see Sanchez-Goni et al. 2008 for some of the story so far).(3) SW Libya between development and conservation
Marina Gallinaro, from the University of Rome, presented on the Holocene records of the Libyan Sahara. She highlighted the issues of preservation of these records in light of the development in the Libyan south, which is having wide impacts. What struck the audience perhaps most was the puzzling motication for the human destruction/ graffiti of the rock art in the region.
(4) Human economic impacts of the Saharan interior: The case of addax
Tim Wacher from the Sahara Conservation Fund kept us in the realm of the impacts of humans, this time from the wildlife perspective. He used the example of tracking the behaviour of the addax Addax nasomaculatus, and their response to traditional human caravan routes through to modern mineral extraction. The population is currently around 200. Aerial surveys and sight reports were used. In summing up he examined: What are the causes of econimc impacts in deserts? – the need for oil, coming from outside the Sahara (e.g. China). What are the shifts in biodiversity? –this will depend on knowledge and attitude of the developers. It is not necessary to crash across the system. Development can be more sensitive to the ecology and this is what the Sahara Conservation Fund is working hard with the government to achieve.
(5) The Mali wetlands: predicted river flows, inundation and water resources
Simon Dadson, working at the Centre for Ecology and Hydrology, presented results from land surface- atmosphere modelling study, looking at impacts of changing water resource management on evaporation from the land surface in the Mali wetlands. The land surface is sensitive to configuration of soil moisture and other available moisture. Looking at the feedbacks from the large wetland innudation to atmospheric moisture, which provides lots of local rainfall and storms (up to 50% more). They are striving to understand how far this impact reaches – what is the footprint – few 100 km or even further into the regional climate. If we manage these water resources, perhaps we are also impacting regional climate? With a proposal to build a large dam, this will increase rice production, but effect bird populations, also downstream flows and perhaps regional climatology.
(1) Groundwater and irrigation in Balochistan Pakistan
Daanish Mustafa, from King’s College took us to the semi-arid province of Balochistan in Pakistan where there is a transition in the approach to irrigation from the traditional karez system to groundwater pumping via tubewells. In this water scarce area groundwater is the mainstay and the past and future of drylands is ties to this. There is a connection between water use and cultural and political Talibanization, with a change to community leadership structures as the technologies of water use change. Water is the key to more than livelihood, and is deeply connected to culture/ identity and community. Whilst land is almost infinite, water is precious. Kareez used to work on a principal of access to water over a certain number of hours and the division of upstream and downstream access helped to ensure the sustainable preservation of the water in the Kareez. The tubwells have disrupted this and put access to water into the hands of the few, who have become very powerful. The predatory pumping of water has facilitated inappropriate farming, such as apples and coriander, which are not the right crops for this region. Daanish argued that protection of the kareez irrigation is an environmental, economic and social necessity, and this must be at the core of development objectives for a sustainable future.
(2) Inferences on retrospective climate of the Thar desert through luminescence dating of aeolian and lacustrine sequences.
Ashok Singhvi, from the Physical Research Laboratory, Ahmedabad, India claims to take us back to drier topic – geomorphology, archaeology and palaeoenvironment (but in fact right back into my direct area of interest). He showed a fascinating brief historical overview of the work that has been done in the region since the 1970s (with lots of contribution by Oxford geographers and archaeologists, from Martin Williams, Andrew Goudie, through the work of the RLAHA in the region today with Mike Petraglia). He highlighted that to cover the Quaternary record in this talk would take a rate of 100 ka per minute!
Some very important major messages were reiterated by Ashok:
a) the sedimentary record is episodic – short periods of intense aggradation and long periods of quiescence. Issues of thresholds, timelags and preservation must be considered.
b) gradients: climatic gradients and changing boundaries of dune activity through time.
c) the vital importance of stratigraphical information alongside chronological data, for example digging trenches in aeolian units and also using thin sections. The concentration of carbonate in some regions of the sand were high enough to rewuire 8 m depth of sand, but this no longer existed. The thin sections revealed a stacked sequence, so in fact the calcrete had formed during multiple cycles beteween 62 and 58 ka in which sediment was depoisted, then removed, aggradated again, and then removed.
d) short windows available for aeolian accumulation and preservation (a 13 ka peak in the record). This message, reiterated from Nick Lancaster and others at INQUA in 2007 – ‘small windown of opportunity’ for accumulation, relating to sediment supply, windiness and vegetation (with a useful figure to illustrate has these things relate to sand mobility).
e) with human activity the rates of dune migration appear to have increased tenfold (from 0.9 cm/y to up to 9 cm/y)
f) a break down of the old (and still regurgitated) view of the LGM as a peak of aeolian accumulation. In fact the peak of aeolian accumulation is well after this, and is a period of transitional climate in which the active/stable dune boundaries have progressively shifted over a gradient from SW to NE.
g) environmental changes and response to climate does not need to be synchronous, and indeed does not appear that way in the preserved record!
Other important ideas Another important message is about climatic gradients in the Thar desert.
(3) Living off uncertainty
Saverio Kratli, editor of Nomadic People spoke about the problems faced when trying to understand rangeland ecology because of the failure of standard statistical techniques to capture the true nature of the system (asymmetric distributions, upon which dryland pastoralism relies upon). Things such as nutrient concentration are unstable and distributed asymmetrically, and understanding this is vital if we are to maximise production of economic value. Pastoralism exploits this asymmetric distribution of nutrients with herders monitoring the animals, rather than the grasslands and making sure that the animals have access to the best available grass, rather than simply eating ‘more grass’. In summary: (1) instability is not an obstacle, even if it seems as one (2) however, resource-scarcing models still frame unpredictable ecological variability as unfavourable and (3) the tools we use to analyse are not correct and exclude the approach of pastoralism. The statistical approaches that have been used hide exactly that which they are supposed to highlight.
see some of his work here
(4) Knowledge systems have not served the drylands well
Mike Mortimer continued the theme of questioning the underpinnings of approaches and knowledge systems with respect to drylands. He reflected on the knowledg e system and how to influence policy makers. The role of stakeholders in knowledge systems is complex and we need to understand the geography of scientific knowledge uptake. There are multiple paradigms, the access to science varies, students from dryland environments that move away to study can be treated as outsiders once they return. There are many myths that hang around in the understanding of drylands, and it can be hard to break these down.
(5) Water landscapes in Central Sahara
Savino di Lernia from the University of Rome took us back to Sahara from the final time in day 1. The main aim of his work Water in the Desert was to assess the water resources available in the area – producing a repetory of the natural (gheltas) and artificial (excavated wells and abonkor) water-related features for the first time, from the Mountains in SW Libya in the southern Sahara . The second aim was to analyse the relation between water and people in prehistory. He considered use of water since the beginning of the Holocene (through rock art) to the present. This work finds that the distribution, size, geomorphological context, vegetal landscape, period of activity and accessibility are key factors for the understanding of the role of water points, settlement systems and mobility strategies within the kel Tadrart Tuarge community.
‘FROM DICK TO THE DESERT: A SHORT (AND IN COMPLETE) HISTORY OF OXFORD GEOGRAPHY’S CONTRIBUTIONS TO DESERT SCIENCE’
Dave Thomas gave us the keynote address at the close of the day, something ‘non-academic’ in a sense, to mark the first integrated deserts conference in Oxford, he put together a (likely incomplete, and occasionally error filled) history of Oxford Geography to desert science.
Listen to the podcast for an entertaining and informative history!
The talk has a focus on the natural-based environment side of Oxford desert geography. It is a great to feel a part of such a distinguished community – even if Oxford Deserts work started in Cambridge!
… and Day two.
(1) Hominin dispersals and the Middle Palaeolithic of Arabia
Huw Groucott from the School of Archaeology in Oxford brought us back to topic that started day 1, taking us to one of the regions introducted by Mike Petraglia – the Arabian Peninsula, and particularly Saudi Arabia. His focus is on pluvial records, from alluvial fans, palaeolakes, palaeosols, speleothems and hippo teeth. The reulsts from his reconnaiscance trip has identified 25 new sites wih middle palaeolithic significance – many with lithic artefacts. It will be very important to find examples of buried artefacts, rather than surface lithics, as these can be put into context and most importantly dated. This will extend the understanding of hominin occupation past the Holocene and into MIS 3, which is a debated pluvial in the region. Previous work in this region by Mike Petraglia and his team is published in Antiquity.
(2) The role of the desert in forming the ancient Egyptian civilization
Mohamed Abouelata from King Saud University, Saudi Arabia talked about the formation of ancient Egyptian civilization and the role of the desert. He shed light on how the civilization used the resources of the desert. For example, use of 7 soft quaried stones for buildings, mining of metals and gemstones for arts, burial and preservation of bodies in the dry sand of the desert. The role of the desert resources may lead us to replace the famous motto of Herodutus ‘Egypt is the gift of the Nile’ with ‘Eygpt is the gift of the desert’.
(3) Water infrastructure and innovative technologies in arid climates
Lisa Mol, presented this paper on behalf of Asisa Chaouni and Liat Margolis from the Department of Architecture, University of Toronto, Canada. This work inv estigates the water infrastructures in cities as components that are rarely viewed as ground for designers. In desert climates the efficiency v. conservation dialectic is at its most extreme. Some of the innovative technologies that support water infrastructure in arid urban centre were presented and analyzed. See more about their work in thisBlog talking about strategies against desertification.
(4) a break from the Programme line up – Maria Mango stood in, with a talk about Androna in the Mediterranean, and a site, which was a staging post on a Roman Road.
This large site (160 ha) has different boundary walls. Was the expansion and contraction linked to climate or invasions? She spoke about the hectares of land needed to support the different sizes of population.
(4) “The cake will be shared by all” in the urban desert: The Black Panthers of Israel 1971-1975.
Anne-Marie Angelo a PhD student at Duke University gave us a history of the Black Panthers movement/ political party in Israel, which was in operation briefly from 1971-1975. This movement was modelled on the US Black Panthers.
(1) Environmental change in oasis systems
Caroline King, a DPhil student, here in the School of Geography, University of Oxford, presented the results of environmental changes over the past 50 years in oasis systems from 3 sites – Nefzaoua, southern Tunisia and the north of the Western Desert of Egypt. This research uses a mixture of remote sensing, national statistical data and research archives alongside surveys of the cultivators in this region to identify the environmental changes that have taken place. In particular, Caroline highlighted issues regarding how to manage these water resources. For example, whilst some attempts have been made to reduce use by concreting up wells, this only leads to the water emerging elsewhere.
(2) Wet rocks, big trouble? Using novel techniques to assess rock art deteriotation.
Lisa Mol stepped back up, this time to give us an insight into her research into rock weathering. This work involves measurements of rock surfaces both out in the splendour of the Golden Gate National Park in South Africa and in the laboratory. Lisa uses ERT (electrical resitivity tomography) to investigate internal moisture within the sandstone rocks. The rows of electrodes shoot 12 V of electricity into the rocks. Over a periods of just 1 year there are dramatic changes in the profiles measured between two field seasons. Lisa showed us these results alongside data-loggers of temperature in the field. In the laboratory the role of moisture and heat has been investigated. Add salt to the sandstone and weathering accelerates!
Lisa has two publications relating to this work so far… In Archaeometry andGeomorphology.
(3) A new estimate about the evaporation in the deserts of northwestern China
Xiaoping Yang, from the Institue of Geology and Geophysics, Chinese Academy of Sciences, Beijing presented his new estimates of annual evaporation from the Taklamakan and Badain Jaran Deserts in China. One of the particularly fascinating parts of the presentation for me were photographs of perched water/moisture in sections cut through these dunes. These contain moisture contents as high as 10-15%. The presence of these small pockets of moisture may help explain the ability for plants to persist and for the ‘green-ness’ of the desert (and maybe sustain those Gerbils we met at Narabeb in the Namib Sand Sea?).
Mean annual rainfall has previously been reported to be as high as 2600mm to 4000 mm in the study region. However, new estimates from Xiaoping, using a modeified Penman Equation and weather station records suggest lower values – of around 1040 mm from lake surfaces and ~ 100 mm from the land surface in the SE part of the Badain Jaran Desert. The use of evaporation pans to previous estimate rates is not necessarily very representative of what is happening at the land surcace. If we are thinking of ‘myths’ – things that get reported as fact might not be true. The metal pan is different from sand.
The implication of these reulsts is that as much as 5 % of modern precipitation could be infiltrating to the groundwater aquifer (and lead to recharge!). This contrasts with the findings of John Gates and Mike Edmunds that recharge rates were ~ 1.7 % or lower. See publications in Hydrogeology Journal, and The Holocene.
All interesting food for thought re. my future research plans.
(4) Gateway of India: the implications of palaoenvironmental change in the Thar desert, NW India, for the dispersal of Homo Sapiens.
James Blinkhorn, from the School of Archaeology in Oxford, gave us the final installment of the hominin dispersal story, and also allowed us to return to the Thar Desert for the second time this conference. The Thar is thought to have been one of the last inhabited regions on a latitudinal belt before humans move north and south. There are some particular controversies over environmental conditions inOIS 3.
There has yet to be a systematic investigation of the rich Palaeolithic archaeological record in the Thar desert to investigate the dispersal of Homo sapiens and this has not been integrated effectively with the palaeoenvironmental record.
James outlined his planned season of fieldwork, which will help to address disparitied between the palaeoenvironmental and archaeological evidence.
(5) Environmental changes in the arid-semi arid western Pampas
Marcelo Zarate fromthe Universidad Nacional de La Pampa, Soanta Rosa, Argentina presented the work by Quaternary geologists and sedimentologists from Argentina in the Western Pampas, focussing on the last episode of activation. This occued during the 1930 decade, and seems to have a parallell with the dust bowl times. Was there an interhemispheric linkage?
(1) Modelling the emission and transport of Saharan dust
Jamie Banks from Atmospheric Physics, here in Oxford presented his results of 3D modelling desert dust lifting and transport and compared this with predicted mineral dust loading over the Saraha from AERONET ground stations and satelitte instruments (SEVIRI, AATSR and MODIS). This region produces a LOT of dust – 1157 Tg in the period between March 2006 and Febuary 2007. The model predicts the path of transport with reasonable accuracy, and 62 Tg of this dust makes it make off the coast of west AFrica into the Atlantic.
(2) Casting new light on late Quaternary environmental and palaeohydrological change in the Namib desert: a review of the application of OSL.
My turn (Abi Stone) to talk about role that OSL has played since 2002 in improving our understanding of palaeohydrological and palaeoenvironmental change in the Namib Desert. There are three important developments: (i) understanding dune migration rates in large complex linear dunes, alongside use of ground penetrating radar (GPR) to establish sedimentological strucutres; (ii) application alongside detailed fluvial lithofacies approaches which have been vital for clarifying the palaeohydrological interpretations of the deposits of the ephemeral rivers that cross the Namib Desert and (iii) applicaiton to sand units that interbed water-lain calcareous rich units, to revise the 14C chronologies, based on unreliable open-system carbonate systems. Watch this site for news of finishing this review paper…
(3) Minimum carbon payment along an aridity gradient for dryland forestation
Henri Rueff from the Centre for Development and Environment, University of Bern presented the economics of reforestation in Non Annex I dryland countries. Planting trees in these regions has an important impact on carbon drawdown, and the farmers are being payed for this carbon drawdown. Henri compared 30 years of the net productive value from carbon with net productive value from agriculture to consider whether this is worthwhile for farmers. There are issues relating to the amount of water the tree plantations take, as compared to agricultural land use. The policy implications are putting structures and intermediaries in place to ensure yearly payments to the farmers (rather than one bulk payment). The Clean Development Mechanism, whilst attractive to government agency must also be worthwhile for famers.
(4) Soil moisture and feedback cycles: southern Africa as a carbon sink.
Andrew Thomas from Manchester Metropolitan University, kept us both informed and entertained in the last presentation of the conference with an excellent presentation on the weird and wacky world of semi-arid soils, biological crusts and CO2.
Current understanding of dryland respiration is insufficient to enable prediction of the consquence of these changes for soils of CO2 fluxes. Using a transect of sites in the Kalahari Andrew and colleagues have determined the effect of temperature, light and moisture on the soil inorganic carbon balance using what look like minature greenhouse pods from which to collect the gas for analysis.
Soil moisture is the primary limiting factor to respiration, with increases in (simulated) rainfall. Wet soils, plus higher temperatures further increase respiration (hotter northerly sites losing more organic carbon after rainfall than cool southerly sites). The autotrophic organisms in the biological crusts respond very quickly to rainfall, creating a temporarily ‘green’ surface. These photosynthesise, take up CO2, therefore muting net respiration rates.
Their revised model considers the complexity biological crusts add to diurnal variations in soil respiration. Predictions for the future are that warming will lead to higher soil carbon losses from the Kalahari Sands due to respiration, and that intensification of grazing results in the break-up of the crusts further increasing atmospheric CO2.
Posters were displayed alongside a wonderful gallery of desert-research photographs that featured on the BBC Earth News. Poster topics ranged from Hot Rocks to Dry Trees. Posters were by
CaitlinManal Abou El-Kassin and Mohamed Hossain from Fayoum University, Eygpt; Christine McCullough from OUCE; Lisa Mol from OUCE; Troy Sternberg from OUCE; Heather Viles from OUCE; Vanessa Winchester from OUCE; Yang Yu from Department of Sociological Studies, University of Sheffield.