Transcript (MS PowerPoint Document, 10.0 MB) Susan

Protecting indigenous
biodiversity
in the eastern South Island
rainshadow zone
Susan Walker
Lance McCaskill Memorial Lecture
Forest & Bird North Canterbury Branch
Annual General Meeting
WEA, Christchurch
9 June 2010
Structure of my talk
1. South Island drylands: characteristics and challenges
2. Pre-settlement dryland ecology
Radiations and endemism
The rule and role of birds and reptiles
All but fire-free
3. Humans and the transformation of ecosystems
Post-settlement period
Pastoral period
4. Where to from here?
Four trends in drylands today
The case for a return to woody dominance
Retreating opportunities
Structure of my talk
1. South Island drylands: characteristics and challenges
2. Pre-settlement dryland ecology
Radiations and endemism
The rule and role of birds and reptiles
All but fire-free
3. Humans and the transformation of ecosystems
Post-settlement period
Pastoral period
4. Where to from here?
Four trends in drylands today
The case for a return to woody dominance
Retreating opportunities
New Zealand drylands
East of main axial
ranges
Annual Penman
Moisture Deficit
>270 mm
(monthly evaporation
minus monthly rainfall, in
mm, summed across 12
months)
Area ~ 53,000 km2
(20% of NZ)
http://www.doc.govt.nz/upload/documents/science-and-technical/SFC258.pdf
Canterbury’s drylands
ENVIRONMENT TYPES
Southern and inland
environments
G: Inland southern South
Island basins and valley
floors
H: Mackenzie Basin and
Central Otago hillslopes
Northern and coastal environments
B. Dry hill country (characteristic of North
Island drylands, more widespread there)
D. Coastal Marlborough and Kaikoura
Coast low relief alluvium & loess
E: Marlborough and North Canterbury
hillslopes
F: Canterbury Plains, Banks Peninsula and
Otago inland basin alluvium and loess
South Island dryland ecosystems
Characteristics
Remaining native ecosystems and species are some of New
Zealand’s most transformed, least protected and most
threatened
Threat classification for land
environments
Category
Category Criteria
Category Name
1
<10% indigenous cover left
Acutely Threatened
2
10–20% left
Chronically
Threatened
3
20–30% left
At Risk
4
>30% left and
<10% protected
Critically
Underprotected
5
>30% left and
10–20% protected
Underprotected
6
>30% left and
>20% protected
Less Reduced and
Better Protected
“THREATENED
ENVIRONMENTS”
Canterbury dryland environments
THREATENED
ENVIRONMENTS
100
80
% LOSS of indigenous cover
since European settlement, by
elevation zone
60
40
20
0
0 to 400m 400 to 800m
Canterbury’s 103
Acutely and
Chronically
Threatened plants
(2005 threat
classification
categories)
800 to
1200m
1200 to
1600m
60
No. of Acutely and
Chronically
Threatened plants
% LOSS of indigenous cover
in elevation zone
Canterbury Region (~2005)
>1600 m
Distribution of threatened plants
40
20
0
Lowland
Montane
Subalpine & Alpine
South Island dryland ecosystems
Characteristics
Remaining native ecosystems and species are some of New
Zealand’s most transformed, least protected and most
threatened
Ecosystems are unstable (not at equilibrium) and much invaded
South Island dryland ecosystems
Characteristics
Remaining native ecosystems and species are some of New
Zealand’s most transformed, least protected and most
threatened
Ecosystems are unstable (not at equilibrium) and much invaded
Major conservation challenges
Extremely low awareness of dryland biodiversity and its
protection needs (community and agencies)
Limited knowledge, experience and science to support
management for biodiversity protection
Some of Canterbury’s dryland communities
Kowhai Bush, Kaikoura
Kanuka & mixed broadleaved forest and shrubland, with
scattered podocarps
Rakaia Island
communities
Kanuka forest,
kowhai remnants,
dry shrubland
Riparian kowhai/lowland
ribbonwood remnants, South
Canterbury
South Canterbury
shrubland and forest
remnants
Fierce lancewood
Pseudopanax ferox
Hector’s tree daisy
Olearia hectori
Limestone communities,
North Canterbury
Limestone communities,
South Canterbury
Gentianella calcis subsp. taiko
Mcleans Island
grasslands
Birdlings Flat/
Lake Forsyth
shrublands
South Branch Hurunui
valley floors and gorge
Ashburton Basin
floor grasslands,
shrublands and
wetlands
Mackenzie Basin
foothills
Mackenzie Basin
floors
Mackenzie Basin floor
23% of
Canterbury’s
‘Threatened’ and
‘At Risk’ plants,
and
11% of
Canterbury’s
‘Data Deficient’
plants
Mackenzie Basin floor
Threatened and At Risk flora
31 species
Wetlands
and their
margins
and turfs
33 species
Grassland
and
shrublands
Mackenzie
Basin floor
Diverse, endemic,
threatened
invertebrates
Moth, grasshopper
and beetle faunas
especially rich &
distinctive
Canterbury’s drylands
ENVIRONMENT TYPES
Southern and inland
environments
G: Inland southern South
Island basins and valley
floors
H: Mackenzie Basin and
Central Otago hillslopes
Remaining opportunities for dryland biodiversity
conservation
Dryland Types
14000
Woody
Grassy
12000
Intensively
developed
10000
Area (km2)
mixed
native-exotic
8000
6000
4000
2000
0
A
B
C
D
E
Dryland type
F
G
H
Structure of my talk
1. South Island drylands: characteristics and challenges
2. Pre-settlement dryland ecology
Radiations and endemism
The rule and role of birds and reptiles
All but fire-free
3. Humans and the transformation of ecosystems
Post-settlement period
Pastoral period
4. Where to from here?
Four trends in drylands today
The case for a return to woody dominance
Retreating opportunities
Radiations and endemism
Likely drivers
•Absence of
forest
•New habitats &
vacant niches
‘Permanent’
barriers
(mountains,
geological
islands)
•Isolation
Temporary
barriers i.e.
glaciations
Pleistocene
Dryland radiations & endemism
Native brooms
“The species exhibit remarkable diversity, from
trees to prostrate forms a few centimetres high”
(Bevan Weir, NZ Rhizobia)
Brachaspis grasshoppers
‘Nondiadromous’
galaxiid fishes
Lowland longjaw
Upland longjaw
Bignose galaxiid
Pencil galaxiids
of the
Mackenzie
Basin
On land, birds and lizards ruled
“No where else had birds evolved to
become the ecological
equivalent of giraffes, kangaroos,
sheep, striped possums, longbeaked echidnas, and tigers”
(Tim Flannery, The Future Eaters)
Mega-bird herbivory
Diversity of
moa sizes and
feeding habits
Grazers
Finschs duck
Teal
Takahe
Browsers
Tree
munchers
Pachyornis
Olearia gizzard twigs
Gizzard stones
Arboreal
defoliators
Frugivores and
seed dispersers
Frugivores and
seed dispersers
Lizards too!
Pollinators
Understorey
scratchers
and bashers
Turfmaintenance
crews
Bird legacies in
the flora
Turfs
Bird defense mechanisms?
Inpenetrable
Unappetising (dead)
Armoured
Inaccessible
fleshy-fruited shrubs
and their imitators!
Big suite of endemic (non grass) herbs
(many now threatened)
No N-fixing herbs!
Pre-settlement ecosystems
All but fire-free
“... a bioclimatic zone, possibly unique on a
global scale, which was dry, drought-prone
but free of all but infrequent fire.
The anomalous result is that New Zealand
possesses a suite of shrubs and trees tolerant
of dry, droughty conditions but highly
sensitive to fire and slow to recover in its
wake” (McGlone 2001, NZJ Ecol)
Tough and slow woody plants
Weeping matipo, Myrsine divaricata
Mountain wineberry, Aristotelia fruticosa
No weedy northern hemisphere conifers to march across the landscape
Tough and slow grasses
•Slow nutrient acquisition
•Slow nutrient use
•Slow growth
(Craine & Lee 2004, Oecologia)
•Tough (high tissue density) leaves
and roots
•Low in nitrogen
Few nutritious, fastgrowing sward-forming
grasses
Australia
North America
South Africa
New Zealand
Conservative birds and lizards
•
•
•
•
Slow growth rates
Long time to maturity
Low fecundity
Long-lived
The slowest bird on earth
North Island Brown Kiwi: slowest growth rate of any bird
anywhere! (McLennan et al. 2007)
Structure of my talk
1. South Island drylands: characteristics and challenges
2. Pre-settlement dryland ecology
Radiations and endemism
The rule and role of birds and reptiles
All but fire-free
3. Humans and the transformation of ecosystems
Post-settlement period – creation of the grasslands
Pastoral period – transformation of the grasslands
4. Where to from here?
Four trends in drylands today
The case for a return to woody dominance
Retreating opportunities
Time, warming >>
The arrival of humans
Beech
Podocarps
(bird
dispersed)
Grasses
Shrubs and small trees
(wind, then bird dispersed)
Clarks Junction fossil pollen trends through the Holocene (from McGlone 2001, NZ Jecol)
20
300 to 400
700 to 800
1100 to 1200
1500 to 1600
1900 to 2000
2300 to 2400
2700 to 2800
3100 to 3200
3500 to 3600
3900 to 4000
4300 to 4400
4700 to 4800
5100 to 5200
5500 to 5600
5900 to 6000
6300 to 6400
6700 to 6800
7100 to 7200
7500 to 7600
7900 to 8000
8300 to 8400
8700 to 8800
9100 to 9200
9500 to 9600
9900 to 10000
Years before present (BP)
10300 to 10400
0
Time
15
10
Frequency (n = 242)
Eastern South Island fire history
Frequency of dates from subfossil charcoals, South Island
(summed in 100-year intervals):
30
25
5
References: McGlone (2001) NZJ Ecol; Rogers, Walker & Lee (2005) Science for Conservation
Grass pollen %s
in cores
Enormous postsettlement
increase in SI
dryland
grass pollen
percentages
0-5%
5-10%
10-15%
15-25%
25-75%
Pre-settlement
Rogers, Walker
& Lee 2005
Science for
Conservation
Post-settlement
Grass pollen percentages (same data)
100
Percentage of pollen sum (%)
Pre-settlement
Post-settlement
80
60
40
20
0
Otago sites
Rogers, Walker
& Lee
Science for
Conservation
Canterbury sites
Marlborough
Creation of the grasslands
A few tussock species spread far and wide
Slim snow
tussock
Midribbed
snow tussock
Red tussock
Narrowleaved snow
tussock
Those with most rapid growth rates!
enabled by
•‘mast’ seeding: periodic massive
seed production
•longish (>decades?) fire return
times
Lloyd, Lee &
Wilson (2002)
Conservation
Biology
New Zealand
grasses recover
slowly from
disturbance
Recovery following
burning
Chionochloa rigida
13 Otago sites with known fire
history,
Measurements taken in 1989
at 1 to 26 years since burning
Some
characteristics
have not fully
recovered in 30
years
Gitay, Lee, Allen & Wilson
(1992) Journal of Environmental Management
TIME SINCE LAST BURNING>>>
New Zealand
grasses recover
slowly from
disturbance
Payton, Lee, Dolby & Mark
(1986) NZJ Botany
UNBURNED
Bracken (for the first
time) and scrub on
steeper land
•Different stages of
recovery from infrequent
Maori fires
•Abundance of palatable
plants
•Herbivore vacuum
Creation of the grasslands:
summary
A one-off! Unique combination of circumstances
• Infrequent (>decades?) but massive fires: a radical new
disturbance
– A few species were pre-adapted and did well (most didn’t)
• No weeds
• 500 years of (virtually) no herbivores
The period of pastoralism
Transformation of the grasslands
Began with European settlement
Late 19th century over-enthusiasm
“exploitative pastoralism”
• More frequent burning
• High stocking rates
• New plants
O’Connor (1986) TGML
Journal
The period of pastoralism
Transformation of the grasslands
Changes in grassland structure and composition continue today
(perhaps especially in short tussock grasslands) e.g. Connor 1964; O’Connor 1982; Treskonova
1991; Rose et al. 1995; Hunter & Scott 1997; Jensen et al. 1997; Walker & Lee 2000; 2002, Duncan et al. 2001.
Major transitions
Tall tussock grasslands to short tussock grasslands
Short tussock grasslands to degraded herbfields with much bare
ground
• Stature and density of the tussocks reduced
• Decreased diversity and abundance of native species
• Increase in non-native plants
No evidence of equilibrium with
pastoral management!
Three synergies in the transformation of the
dryland grasslands
1. Burning + grazing
2. Domestic + feral grazers
3. Reduced native dominance + exotic invasion
Grazing-only effects:
experimental evidence
Immature tussocks
Chionochloa rigida
(narrow-leaved snow
tussock)
Carrick Range, Otago
“LIGHT” grazing
(control)
“HEAVY” grazing
Grazing affects tussock
regeneration:
a) reduced overall
recruitment
b) reduced proportions small
seedlings
c) reduced seedling height
d) reduced proportion of
seedlings distant from
plant
small tussocks <-
-> large tussocks
small tussocks <-
-> large tussocks
Lee, Fenner & Duncan (1993)
NZJ Botany
Synergy 1. Burning + grazing synergy
Kevin O’Connor’s depiction
Burning alone
Burning + constant
grazing
Burning + increasing
grazing
O’Connor (1982) NZJ Ecology
100
100
Burning + grazing
synergy:
80
80
experimental evidence
60
60
20
20
Mean number of new tillers emerged in the 2 years following
spring and autumn
fires
40
40
Burned only
100
80
60
0
Maungatua 870 m
Spring
Burned and
then regrowth
0
clipped
870
m Peak
Old
ManmRa. 1220 m
Old Man Ra. Maungatua
1220 m
Coronet
1190
Spring
Autumn
Spring
Autumn
Autumn
40
20
0
Maungatua 870 m
Old Man Ra. 1220 m
Coronet Peak 1190 m
Mark (1965) NZJ Botany
Synergy 2. Domestic + feral grazers
Synergy 3: Reduced native dominance
+ exotic invasion
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Towns
Ecological Districts
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Survey evidence
957 quadrats in 47
alluvial systems
Walker & Lee (2000; 2002; 2003)
•Fewer exotic species where structural
dominance of native species is greater
Native dominance
3
Average native dominance score
(for quadrats with n exotic species)
2
1
0
1
2
3
4
5
6
7
8
9
10
11
12
Number (n) of exotic plant species >>
13
14
15
•Main invaders are perennial forbs and grasses
•Relatively few woody invaders
NATIVE
TOTAL FLORA
ANNUALS
Dicot (non-grass!) herbs
Grasses
N-FIXERS
Herbaceous
Woody
PERENNIALS
Dicot (non-grass!) herbs
Grasses
Sedges
Orchids
Trees
EXOTIC
247
79
4
2
12
6
0
5
7
2
116
28
35
5
35
34*
14*
101-
n* = significantly more, n- = significantly fewer than expected (P<0.05 by chi-squared)
Major ecological shifts
(post-settlement and pastoral periods)
Slow bird herbivore fauna, to
boom-bust mammal fauna
Slow woody/shrubby communities with numerous cryptic
non-grass herbs, to
new open grasslands invaded by ‘fast’ light-demanding
exotic plants
– sward-forming grasses & N-fixing herbs,
– northern hemisphere postglacial tree “superweeds”
Structure of my talk
1. South Island drylands: characteristics and challenges
2. Pre-settlement dryland ecology
Radiations and endemism
The rule and role of birds and reptiles
All but fire-free
Herbs and wood
3. Humans and the transformation of ecosystems
Post-settlement period
Pastoral period
4. Where to from here?
Four trends in drylands today
The case for a return to woody dominance
Retreating opportunities
Trends in dryland landscapes today
Intensive agriculture: complete transformation
Continued pastoral use: native grassland dominance
reduced, consolidation of exotic species (especially
mammal grazing-adapted light-demanding forbs
and grasses)
Reduced fire-frequency with relict shrubs: expansion
of mixed unpalatable native-exotic woody
vegetation
Grazing and fire reduced: race between residual
native species and new exotic species
Intensive agriculture
Trends in dryland landscapes today
Intensive agriculture: complete transformation
Continued pastoral use: native grassland dominance
reduced, consolidation of exotic species (especially
mammal grazing-adapted light-demanding forbs
and grasses)
Reduced fire-frequency with relict shrubs: expansion
of mixed unpalatable native-exotic woody
vegetation
Grazing and fire reduced: race between residual
native species and new exotic species
Trends in dryland landscapes today
Intensive agriculture: complete transformation
Continued pastoral use: native grassland dominance
reduced, consolidation of exotic species (especially
mammal grazing-adapted light-demanding forbs
and grasses)
Reduced fire-frequency with relict shrubs: expansion
of mixed unpalatable native-exotic woody
vegetation
Grazing and fire reduced: race between residual
native species and new exotic species
Expansion of mixed, native-exotic woody
vegetation
Trends in dryland landscapes today
Intensive agriculture: complete transformation
Continued pastoral use: native grassland dominance
reduced, consolidation of exotic species (especially
mammal grazing-adapted light-demanding forbs
and grasses)
Reduced fire-frequency with relict shrubs: expansion
of mixed unpalatable native-exotic woody
vegetation
Grazing and fire reduced: race between residual
native species and new exotic species
Tekapo Scientific Reserve, Mackenzie Basin
1992 to 2009
1992
2009
1992
2009
Monitoring Plots 1992 - 2009
Flat Top Hill Conservation Area, Central Otago
(retired & reserved 1993)
2009
Pragmatic dryland conservation goals?
Return to past states is impractical
Today’s grasslands are unstable, and difficult to
maintain as grasslands
“Ecological Integrity” (Lee et al. 2005)
• Species occupancy
– “native species that could and should be present, are present”
• Native dominance
– “native species dominate structure, composition and function”
• Environmental representation
– “across a full range of environments”
The case for a return to woody
dominance in drylands
• Former widespread ecosystems were slow, woody, fire-free
– wood overstorey, non-grass herb understorey
• Major exotic plant invaders and competitors are lightdemanding
Focus of 8-year FRST-funded ‘dryland’ research programme
Facilitating transitions to native woody communities, understanding
associated biodiversity benefits/changes, building understanding
and awareness
Retreating opportunities for dryland
protection
Land use intensification
Land reform (Tenure Review)
14000
12000
Wood
Grass
Intensively
developed
Area (km2)
10000
8000
6000
4000
2000
0
A
B
C
D
E
Dryland type
F
G
H
% of identified significant inherent values
Recommendations and achievements for significant
inherent values in Tenure Review to 2007
100
DOC recommended for protection as public land
90
LINZ achieved protection
80
70
60
More developable land
More threatened biodiversity
50
40
30
20
10
0
<10%
indigenous
cover left
10–20% left
20–30% left
>30% left and
<10%
protected
>30% left and
10–20%
protected
Threat categories from the Threatened Environment Classification (Walker et al. 2007)
Data source: Department of Conservation, unpublished data for 69 of the 90 leases reviewed 1992-2007
>30% left and
>20%
protected
Leases retain more indigenous cover than private land
in the same environments
Indigenous cover retained (%)
100
Leases
Private land
80
60
40
20
0
0
20
40
60
80
100
% indigenous cover remaining in environments
Mackenzie Basin floor
A: 1990
Converted by 1990
B: 2009
Converted by 1990
Converted between
1990 and 2009
Mackenzie Basin
floor leases
B: 2009
Glenmore
Converted by 1990
Converted between
1990 and 2009
Sawdon
Simons
Pass
Grays Hills
Conclusion
Restoring dryland ecological integrity through
woody dominance may be possible
BUT
only if the habitat remains
Thanks!
Ideas, information and photos
Nick Head, Peter Johnson, Jamie Wood, Marieke
Lettink, Geoff Rogers, Di Lucas, Bill Lee, Kelvin Lloyd,
Ines Stager, Emily Weeks
Paul Martinson for his extinct bird portaits
from Tennyson & Martinson, Extinct Birds of New Zealand, Te
Papa Press (available from Manaaki Whenua Press)