what can history tell us about our ability to influence the condition of natural resources?
DESCRIPTION
Presented by Ted Lefroy as part of the 2009 Place and Purpose Symposium run by the Landscape Science ClusterTRANSCRIPT
What can history tell us about our ability to influence the condition of natural resources?
Ted Lefroy
What can history tell us about our
ability to influence the condition
of natural resources?
Ted Lefroy
University of Tasmania
Water quality in Tasmanian rivers and estuaries
Sediment cores, air photos, historical records
Biotic cycles and Large infrequent events
*
Water quality data
Response to intervention
**
Oral history, sediment
cores
Large infrequent events
1. Sediment cores
2. Space-for-time exp.
3. Air photo analysis
4. WQ/veg condition data
5. Historical records
6. Oral history
Historic WQ data,
space for time exp.
Disturbance thresholds for
Tasmanian rivers
Little Swanport
1948
1967
1973
2003
*
*
Sediment cores, air photos, historical records
1. Biotic cycles
2. Large infrequent events
3. Human influence
Epiphyte crash
Seagrass recovery
Seagrass recovery
Catastrophic seagrass decline
Flood or tsunami
Epiphyte growth
Seagrass decline
Catastrophic seagrass decline
Flood or tsunami
Catastrophic seagrass decline
Anthropogenic
C/N ratios, seagrass fragments, biogenic Si,
isotopes, sand, tsunamite, ash
Epiphyte crash
Seagrass recovery
Seagrass recovery
?
Duck, Montagu, Black & Detention
Rivers
*
Duck RiverOral history, air photos, sediment dating
Sediment dating
Oral history
Black River, Detention River
Duck River, Montagu River
Cobble bottom
Mud banks
Water quality data & space-for-time
experiment
AusRivAs dataset 1999 & 2006
781 sampling events
Water quality, Biota,
Geomorphology
Habitat
0
10
20
30
40
50
60
70
80
90
100
0 0.5
Threshold: > 42% grazing
Substituting space for time
Blue - grazing
Hatched - cropping
Green - conservation
Red - forestry
Substituting space for time
flow light temp
terrestrial carbon algal dominated
Threshold 55%
Detecting recovery
The Pet River
*
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
Regeneration = 2 x Revegetation Private investment ~ 2 x Public
Vegetation change 1946-20061946
2006
?
1800 1870 1940 2010
% C
an
op
y c
ove
r
Large Infrequent Events: Gold, Fire
Slow drivers: rabbits, sheep, Landcare, wool prices, tree change
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
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
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
The Environment Institute