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Rock Hyrax Middens and Climate Change in Southern Africa during the last 50,000 years

Final Report Summary - HYRAX (Rock Hyrax Middens and Climate Change in Southern Africa during the last 50,000 years)

The goal of the HYRAX project was to develop a new palaeoenvironmental archive that will for the first time enable the recovery of reliable, high resolution records of long-term climate and vegetation change from southern Africa. This archive is the stratified accumulation of urine and faecal pellets (middens) of the rock hyrax (Procavia capensis) that when solidified may preserve records of environmental change spanning upwards of 50,000 years. When coupled with high-precision chronologies, these environmental proxies (such as fossil pollen and stable isotopes) have the potential to provide multi-millennial records of sub-decadal resolution, suitable for the assessment of both long-term trends and abrupt events.
Despite the southern Africa’s sensitivity to climate change, and its position at a key juncture in hemispheric and global circulation systems, the environmental history of the region remains largely unknown. This is principally due to the region’s semi- to hyperarid climate, which is not conducive to the occurrence of lakes and wetlands that typically preserve long records of environmental change in temperate and tropical regions. HYRAX planned to address a series of unsolved questions regarding past, present and future climate change research that are critical not only for southern Africa, but for our understanding of global climate change as well. These questions, which are relatively well-resolved in much of the Northern Hemisphere, remained unanswered in southern Africa.
• What were conditions like during the Last Glacial Maximum? What was the nature of the transition from glacial to interglacial climates? Did significant regional variability exist? What were the drivers of change?
• How did rapid climate change events impact regional climates?
• How can we expect future climate change to affect regional climates, hydrologic systems, vegetation, and the potential for desertification?
In order to reach its goal, HYRAX proposed to:
1) Use stable isotopes and fossil pollen to determine the environmental history and dynamics at a series of sites across southern Africa.
2) Develop statistical techniques to produce quantitative climate reconstructions from pollen data.
3) Assess the spatial and temporal variability of environmental change across southern Africa during the last 50,000 years.
4) Use data from hyrax middens to integrate data from less well resolved records to achieve a more complete understanding of environmental change in the region.
5) Compare our findings with the latest simulations from general circulation models (GCMs) to evaluate the model simulations, and study climate system dynamics.
HYRAX met and exceeded these goals and expectations. The fundamental goal of the project, to develop rock hyrax middens as an archive, was achieved through technical refinements in the field and laboratory that have allowed us to optimise the collection, preparation and subsampling of hyrax middens for subsequent analyses. This work, combined with the application of some 750 radiocarbon ages to over 100 midden sections from a total of 29 major midden sites near comprehensive insight into how middens form, and how best to exploit their potential. This stratigraphic and chronologic framework has supported the development of an array of high resolution proxy records of environmental change spanning the interface between southern Africa’s tropical and temperate regions. While varying between middens and sites, records of sub-decadal resolution were recovered, as were records extending back an estimated 70,000 years. In more humid regions where middens were found to be absent, we applied a new climate reconstruction tool – CREST - developed by the HYRAX project to derive quantified estimates of specific palaeoclimatic parameters from existing pollen records. In combination, these data have provided the underpinning for an entirely new paradigm for the study and understanding of climate change and dynamics in the region. The analysis and comparison of these continuous multi-millennial, high resolution records is revealing previously unrecognised, unimagined spatio-temporal patterns and events in the region. Most critically, the work of the HYRAX project is for the first time allowing for: 1) the detailed, robust comparison of southern African palaeoclimate dynamics with patterns and phenomena at the global scale, allowing for the consideration of the region in discussions and analyses of global change, and 2) the comparison of our data with GCM simulation to evaluate, modify and improve model performance, and study the drivers and dynamics of climate change.