What can history tell us about our ability to influence the condition of natural resources?

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Presented by Ted Lefroy as part of the 2009 Place and Purpose Symposium run by the Landscape Science Cluster

Presented by Ted Lefroy as part of the 2009 Place and Purpose Symposium run by the Landscape Science Cluster

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  • 1. What can history tell us about our ability to influence the condition of natural resources? Ted Lefroy
  • 2. What can history tell us about our ability to influence the condition of natural resources? Ted Lefroy University of Tasmania
  • 3. Water quality in Tasmanian rivers and estuaries Oral history, sediment Water quality data cores Response to intervention Large infrequent events 1. Sediment cores 2. Space-for-time exp. ** 3. Air photo analysis Historic WQ data, space for time exp. Disturbance thresholds for 4. WQ/veg condition data Tasmanian rivers * 5. Historical records 6. Oral history Sediment cores, air photos, historical records Biotic cycles and Large infrequent events
  • 4. Little Swanport 1948 * 1967 1973 2003
  • 5. Sediment cores, air photos, historical records C/N ratios, seagrass fragments, biogenic Si, isotopes, sand, tsunamite, ash Epiphyte growth Epiphyte crash Seagrass decline Seagrass recovery Catastrophic seagrass decline Seagrass recovery Flood or tsunami Epiphyte crash Seagrass recovery Catastrophic seagrass declinedecline Catastrophic seagrass Anthropogenic Flood or tsunami ? Seagrass recovery 1. Biotic cycles * 2. Large infrequent events 3. Human influence
  • 6. Duck, Montagu, Black & Detention Rivers *
  • 7. Duck River Oral history, air photos, sediment dating Black River, Detention River Cobble bottom Sediment dating Oral history Mud banks Duck River, Montagu River
  • 8. Water quality data & space-for-time experiment AusRivAs dataset 1999 & 2006 781 sampling events Water quality, Biota, Geomorphology Habitat 100 90 80 70 60 50 Threshold: > 42% grazing 40 30 20 10 0 0 0.5
  • 9. Substituting space for time Blue - grazing Hatched - cropping Green - conservation Red - forestry
  • 10. Substituting space for time Threshold 55%  flow  light  temp terrestrial carbon  algal dominated
  • 11. Detecting recovery The Pet River *
  • 12. The Pet River  16 km2 catchment  5-25% of sub-catchments treated  12 sub-catchments monitored for 7 years  No detectable change in N or P
  • 13. Vegetation change 1946-2006 1946 2006 % Canopy cover ? Large Infrequent Events: Gold, Fire Slow drivers: rabbits, sheep, Landcare, wool prices, tree change 1800 1870 1940 2010 Regeneration = 2 x Revegetation Private investment ~ 2 x Public
  • 14. Summary 1 1. Multiple lines of evidence – Sediment cores – Space-for-time experiments – Air photo analysis – Historic WQ/veg condition data – Oral history – Historical records
  • 15. Summary 2 2. In combination, they can be used to identify – Biotic cycles – Large infrequent events – Human disturbance – Recovery in vegetation extent 3. ….but its more challenging to – Document recovery in water quality – Document change in vegetation condition
  • 16. Acknowledgements Estuarine research – John Gibson, Barry Gallagher, Jeff Ross and Christine Crawford Fresh water – Nelli Horrigan, Reg Majierowski, Steve Read and Peter Davies Riparian – Shane Broad, Bill Cotching and Ross Corkery Vegetation change – Garreth Kyle, Dave Duncan, Libby Rumpf and Graeme Newell www.landscapelogic.org.au
  • 17. The Environment Institute