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

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