|Panel debate on 'Tipping Points' Chaired by Prof Ken Gregory|
I was intending to arrive in time for Prof Antony Long's (Durham University) Keynote 'Separating fluctuations from trends: the behaviour of the Greenland ice sheet in the last millennium', but didn't turn up until half way through the subsequent talk by Mark Macklin et al. entitled 'Seeing things whole: database and meta-analysis of fluvial responses to Holocene environmental change'. He talked about river entrenchment events through the Holocene and I noted one event taking place between 1100-700 years ago, but there is not much data from southeast Wales, which is my area of interest here around those dates as an entrenchment event may have taken place there then.
Julian Murton then followed on with his talk 'Permafrost as a driver and record of environmental change'. He covered ice segregation, thermokarst evidence, thermal erosion, and the carbon freezer. He said that unfrozen water migrates towards colder temperatures within the soil, regolith or rock profile, resulting in bidirectional or unidirectional flow depending on the season (upward in the winter, downward in the summer, and up and down (bidirectional) in the autumn). Bidirectional freezing leads to fracturing along the top of the permafrost boundary, whilst unidirectional freezing (in the winter) leads to fracturing near the ground surface. Something that was a little counter-intuitive is that a lot of frost heave takes place in the summer as water migrates downward to feed ice lenses. He also discussed the formation of thermokarst lakes due to subsidence, and used examples from Kent Chalk and Glamorgan Mercia Mudstone in talking about solifluction in incised valley bottoms, which suffer more severe fracturing due to higher water content. He suggests that valley incision is more likely to have occurred during cold phases under good permafrost conditions into which rivers eroded thanduring warm phases. Regarding carbon sequestered, he stated that some 1672 Gt/C is stored in permafrost, which is a large amount, far more than in the atmosphere, so it would be worrying should the permafrost melt and the carbon released. He also talked about his work on the Yedoma silt in Siberia. It is a significant permafrost unit that covers some 1 million km2 of Russia and contains fossil roots and animal remains. Lastly, he mentioned that he thought the North American glacial Lake Agassiz drained perhaps not eastward through the Gulf of St Lawrence into the Atlantic, but northwest via the Mackenzie Delta system and into the Arctic Ocean.
Before tea, Varyl Thorndycraft et al. talked about the teams research of the rivers Erme in the southwest and Till in the northeast of the UK in 'Towards a quantification of flood response to long-term autogenic and allogenic drivers'. They looked at reconstructing palaeochannels and flood levels, which was interesting given the level of river discharge, such as 416 m/sec. After tea, David Thomas and his co-worker talked about 'Interpreting geoproxy records of late Quaternary climate change in the low latitudes: the challenge of incorporating geomorphological reality in palaeoenvironmental research'. It was an interesting presentation principally about reconstructing complex African Quaternary environments. Marine records are OK, but they don't give much information about terrestrial environments, so lake records are useful. But many of African lake basins lack sediment sequences, and so they argue landforms (geoproxies) are the only indicators available, such as lake shorelines and dunes. However, such geoproxies are difficult to interpret as wet or dry; for example, Nash and Endfield (2008) document extreme wet and dry conditions in the Kalahari region within the space of 60 years! There does seem to be some hope for geoproxy use however, as their sensitivity appears to change across climate gradients.
Prof Adrian Harvey (University of Liverpool) followed with his Linton Lecture on 'The coupling status of alluvial fans and debris cones', and considered the functional and preservational roles of coupling. Fans and streams can be coupled or not e.g. fans forming at the foot of scarp slopes may or may not have streams exiting them. Throughout his presentation, Prof Harvey dispelled some popular 'myths' regarding fans, such as the significance of fining-up or coarsening-up sediment sequences, which simply indicate primary or reworked sequences respectively. He also celebrated recent advances in the field, such as new dating methods, and the arrival of Google Earth as a freely available satellite image resource.
The next presentation was the first 30th International Geographical Congress (IGC) Lecture given by Prof Will Graf (University of South Carolina) on 'Science, policy and politics for the Florida Everglades'. Prof Graf told a story of the Everglades, particularly from a cultural standpoint. The restoration of the Everglades is costing US$17 Billion and is one of a number of river restoration projects in the US each costing over $10 Billion. There are three eras of environmental history: pre-development era up to 1880, development era 1880-1980, and the restoration era post-1980. He romped through Everglade history, mentioning Audubon's ornithology, the Seminole and Miccosukee Tribes, the paintings of George Herbert McCord, Hamilton Disston, Napoleon Bonaparte Broward, Snail Kites, Cape Sable Seaside Sparrow, Wood Storks, Marjory Stoneman Douglas, and Arthur R. Marshall.
- Pre-development era (pre-1880): Everglades comprise a 23,000 km2 drainage basin with broad flows up to 50km across but less than 1m deep (i.e. sheet flow), and relief less than 20m on the Florida peninsula. Documented in 1773 on the first map of Florida as the 'Riverglades', but then changed through a transcription error by 1856 to the Everglades. Audubon in 1838 and McCord in 1878 depict a wildlife-rich (c. 1100 plant species) and idyllic landscape of sawgrass, ridge and slough (shallow channels and low ridges on a bed of peat), and tree islands (occupying bedrock highs).
- Development Era (1880-1980): Disston (1844-1896) started draining the Everglades, which was continued by Broward (1857-1910). Agriculture developed but set back by hurricanes in 1926 and 1928, the latter killing around 3000 Flordians. In 1934, Lake Okeechobee was dredged and levees constructed around its margins, and the number of tree islands later declined dramatically. In 1948, the Central and Southern Florida Project was set up and the reduction of the Everglades contined down to 6,000 km2. The Everglades Agricultural Area established between 1954-1959, and the Tamiami Trail (levee and canal) in 1960, and by the end of the era there were 1300 water control stations and 2017 miles of canals and levees. Bird life also declines through this period e.g. Snail Kites decline to around 1000 individuals, mis-managment of Cape Sable Seaside Sparrow strongholds, and the migration of Wood Storks to water storage areas rather than natural habitats. If development continued to 2060 then almost all of Flordia will be urbanised and over 36 million people would live there.
- Restoration era (post-1980): 1990 Preservation 2000 Act allocated $3 Billion to buy land, 1994 Consent Decree, 2000 Comprehensive Everglades Restoration Plan (CERP), expected to take 60 years and cost $17 Billion comprising 62 projects to help restore natural flows.
The evening concluded with a BSG and RGS-IBG Joint Debate 'Fragile environments: are we at a tipping point'? The debate was introduced by Catherine Souch of the RGS, and Chaired with opening remarks by Prof Ken Gregory. The first speaker was Prof Stuart Lane (Durham University) who equated rapid change with the notion of 'tipping points'. He cited the work of Gladwell and bifurcation theory, the John Humphries effect, and that big catastrophes have big causes, and that people need to better cope with catastrophes when they happen. Prof Sue Smith (Cambridge University) followed and discussed how society deals with collapse and also about the 'ethic of care'. Prof Alan Thorpe (NERC) talked about climate as being quite stable and suggests that tipping points occur when climate flips from one state to another and drew some (later contested) examples from the palaeoclimate record. He then discussed tipping points in the context of future climate change with regard to the melting of the Greenland ice sheet (requiring a temperature rise of 3 degrees C locally), the West Antarctic Ice Sheet (requiring 8 degree C local warming plus sea-level rise), thermohaline circulation, El Nino-Southern Oscillation and its link to Amazon drought, and the Asian monsoon (current Pakistan floods may not be climate related). Lastly, Prof Chris Whitty (DfID) discussed tipping points at different scales, suggesting they are very common on the small scale e.g. extinction of species restricted to isolated hill tops, but that resilience of populations, particularly in developing countries was an important factor in determining the local impact of a disaster. There were some interesting questions from the floor before Prof Gregory summed up and we all made for the wine reception.