The open kickoff meeting of the PAGES working group GloSS aimed to set the boundary conditions that will enable the GloSS-WG to meet its scientific goals within the next three years. Therefore, this workshop focused on the development of a list of proxies/indices of human impacts on soils and sediments that will support the compilation of a global soil and sediment database. A total of 30 participants from different disciplines (geomorphology, geology, soil science, ecology, (palaeo)limnology, hydrology and geoarchaeology) and seven countries and four continents contributed to the workshop.
The first 1 ½ day were dedicated to continental reviews of proxies of human impacts on soils and sediment transfers. The keynotes were given by Gary Stinchcomb (Murray State University), Tim Beach (University of Texas at Austin), Juan Restrepo (EAFIT University of Medellin), Dan Penny (University of Sydney), Hongming He (Chinese Academy of Science), Lishan Ran (National University of Singapore), Rajiv Sinha (Indian Institute of Technology, Kanpur) and Gert Verstreaten (Leuven University). The regional reviews were complemented by a keynote of Jane Willenbring (University of Pennsylvania) on a global view on sediment production and export and a contribution via skype Nicholas McKay (Northern Arizona University) on his experiences building the PAGES 2k database.
During the second and the third day the workshop participants i) developed a concept that organizes proxies of human impact on soil and sediment dynamics for hillslopes, floodplains, lakes and deltas covering different time scales during the Holocene, ii) discussed potential stakeholder, and requirements of a GloSS-database, and iii) discussed its structure and developed a road map for the first three years.
The participants of the breakout discussion group on human proxies agreed that the primary GloSS-data sets should be proxies/indices that focus on soil erosion and sediment transport and deposition and do not include other proxies (such as pollen or diatoms). While volumetric and/or mass balance proxies are generally favoured compared to length per time proxies (such as sedimentation and/or erosion rates given in mm/a), it was noted that length-based rates are an invaluable tool for constructing such sediment budgets and that for many study sites complete quantitative inventories are not available and difficult to obtain. Thus length-based rates were considered as very valuable information that should be considered but interpreted with great care. Regarding the considered timescale, a conservative estimate of the Holocene was decided to be the operational time frame for the GloSS datasets, allowing estimation of natural base line conditions.
The discussion on the database content and structure resulted in the following statements: The GloSS-DB should focus on soil erosion, sediment transport and deposition of the following environments: hillslopes, floodplains/channels, lakes and deltas. There is no need to populate the GloSS-DB with other available paleo-environmental information. Instead, the GloSS-DB should be linked to other existing databases (esp. developed within the PAGES-Community) to avoid redundancy where possible.
The group agreed that human impact on the above-mentioned environments is best described by the change of erosion, transport and/or deposition. Thus, at minimum two ‘time slices’, before and after human impact, for the three variables are necessary. Due to the major challenges to define what human impact actually is and when it starts in different regions of the earth, it was argued that the number of time-slices should be maximize to allow flexible interpretations without constraining what the user can interpret from changes (e.g. climate versus human impacts).
To set the boundary conditions for the first three years of the GloSS working group, a roadmap, seven regional task forces and a database task force was build. The regional task forces and their leaders are: i) Europe and Mediterranean (Gert Verstraeten), South Asia (Rajiv Sinha), Australia / NZ (Bob Wasson, Duncan Cook), East and Central Asia (Hongming He, Lu Xixi), North-America (Jane Willenbring, Gary Stinchcomb), South and Central America (Juan Restrepo), Africa (Klaus Martin Moldenhauer, not fixed at this time). The database task force has following members: Jane Willenbring, Gary Stinchcomb, Veerle Vanacker, Dan Penny, Lishan Ran, Jean Philippe Jenny, Nick Mackay, Kim Cohen and Thomas Hoffmann.
– Written by Thomas Hoffmann, University of Bonn