protecting indigenous biodiversity in the eastern south island rainshadow zone susan walker lance...
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Protecting indigenous biodiversity in the eastern South Island rainshadow zone
Susan WalkerLance McCaskill Memorial LectureForest & Bird North Canterbury BranchAnnual General MeetingWEA, Christchurch9 June 2010
Structure of my talk
1. South Island drylands: characteristics and challenges
2. Pre-settlement dryland ecologyRadiations and endemism
The rule and role of birds and reptilesAll but fire-free
3. Humans and the transformation of ecosystemsPost-settlement period
Pastoral period
4. Where to from here?Four trends in drylands today
The case for a return to woody dominanceRetreating opportunities
Structure of my talk
1. South Island drylands: characteristics and challenges
2. Pre-settlement dryland ecologyRadiations and endemism
The rule and role of birds and reptilesAll but fire-free
3. Humans and the transformation of ecosystemsPost-settlement period
Pastoral period
4. Where to from here?Four trends in drylands today
The case for a return to woody dominanceRetreating opportunities
New Zealand drylands
http://www.doc.govt.nz/upload/documents/science-and-technical/SFC258.pdf
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)
ENVIRONMENT TYPES
Southern and inland environments
G: Inland southern South Island basins and valley floors
H: Mackenzie Basin and Central Otago hillslopes
Canterbury’s drylands
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
CharacteristicsRemaining native ecosystems and species are some of New
Zealand’s most transformed, least protected and most threatened
Threat classification for land environmentsCategory 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 ENVIRONMENT
S”
Canterbury dryland environments
THREATENED ENVIRONMENT
S
Canterbury Region (~2005)
Distribution of threatened plants
% LOSS of indigenous cover since European settlement,
by elevation zone
% L
OS
S o
f in
dig
en
ou
s c
over
in e
levati
on z
one
No.
of
Acu
tely
an
d
Ch
ron
ically
Th
reate
ned
pla
nts
0
20
40
60
80
100
0 to 400m 400 to 800m 800 to1200m
1200 to1600m
>1600 m
Lowland Montane Subalpine & Alpine
0
20
40
60
Canterbury’s 103 Acutely and Chronically
Threatened plants(2005 threat classification categories)
South Island dryland ecosystems
CharacteristicsRemaining 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
CharacteristicsRemaining 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 challengesExtremely low awareness of dryland biodiversity and its
protection needs (community and agencies)
Limited knowledge, experience and science to support management for biodiversity protection
Kowhai Bush, KaikouraKanuka & mixed broadleaved forest and shrubland, with scattered podocarps
Some of Canterbury’s dryland communities
Rakaia Island communities
Kanuka forest, kowhai
remnants, dry shrubland
Riparian kowhai/lowland ribbonwood remnants, South
Canterbury
Hector’s tree daisy Olearia hectori
Fierce lancewoodPseudopanax ferox
South Canterbury shrubland and forest
remnants
Limestone communities, North Canterbury
Limestone communities, South Canterbury
Gentianella calcis subsp. taiko
Mcleans Island grasslands
Birdlings Flat/Lake Forsyth shrublands
South Branch Hurunuivalley floors and gorge
Ashburton Basin
floor grasslands, shrublands and
wetlands
Mackenzie Basin foothills
Mackenzie Basin floors
23% of Canterbury’s ‘Threatened’ and ‘At Risk’ plants,
and 11% of Canterbury’s ‘Data Deficient’plants
Mackenzie Basin floor
Mackenzie Basin floor
33 species Grassland and shrublands
31 species Wetlands and their margins and turfs
Threatened and At Risk flora
Diverse, endemic, threatened invertebrates
Moth, grasshopper and beetle faunas especially rich & distinctive
Mackenzie Basin floor
ENVIRONMENT TYPES
Southern and inland environments
G: Inland southern South Island basins and valley floors
H: Mackenzie Basin and Central Otago hillslopes
Canterbury’s drylands
Remaining opportunities for dryland biodiversity conservation
Dryland Types
0
2000
4000
6000
8000
10000
12000
14000
A B C D E F G H
Dryland type
Are
a (
km2)
WoodyGrassy
Intensivelydeveloped
mixed native-exotic
Structure of my talk
1. South Island drylands: characteristics and challenges
2. Pre-settlement dryland ecologyRadiations and endemism
The rule and role of birds and reptilesAll but fire-free
3. Humans and the transformation of ecosystemsPost-settlement period
Pastoral period
4. Where to from here?Four trends in drylands today
The case for a return to woody dominanceRetreating opportunities
Radiations and endemism
Pleistocene
Likely drivers
•Absence of forest
•New habitats & vacant niches
•Isolation
‘Permanent’ barriers (mountains, geological islands)
Temporary barriers i.e. glaciations
Dryland radiations & endemismNative brooms
Brachaspis grasshoppers“The species exhibit remarkable diversity, from trees to prostrate forms a few centimetres high”
(Bevan Weir, NZ Rhizobia)
‘Non-diadromous’
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, long-beaked echidnas, and tigers”
(Tim Flannery, The Future Eaters)
Mega-bird herbivory
Diversity of moa sizes and feeding habits
Grazers
Finschs duck
Takahe
Teal
Browsers
Tree munchers
Pachyornis
Olearia gizzard twigs
Gizzard stones
Arboreal defoliators
Frugivores and seed dispersers
Frugivores and seed
dispersersLizards too!
Pollinators
Understorey scratchers and bashers
Turf-maintenance crews
Turfs
Bird legacies in the flora
Unappetising (dead)
Armoured
Inaccessible
Inpenetrable
Bird defense mechanisms?
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)
Weeping matipo, Myrsine divaricata Mountain wineberry, Aristotelia fruticosa
Tough and slow woody plants
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)
North America
New Zealand
Australia
South Africa
•Tough (high tissue density) leaves and roots•Low in nitrogen
Few nutritious, fast-growing sward-forming grasses
Conservative birds and lizards
• Slow growth rates • Long time to maturity• Low fecundity• Long-lived
North Island Brown Kiwi: slowest growth rate of any bird anywhere! (McLennan et al. 2007)
The slowest bird on earth
Structure of my talk
1. South Island drylands: characteristics and challenges
2. Pre-settlement dryland ecologyRadiations and endemism
The rule and role of birds and reptilesAll but fire-free
3. Humans and the transformation of ecosystemsPost-settlement period – creation of the grasslandsPastoral period – transformation of the grasslands
4. Where to from here?Four trends in drylands today
The case for a return to woody dominanceRetreating opportunities
The arrival of humans
Clarks Junction fossil pollen trends through the Holocene (from McGlone 2001, NZ Jecol)
Beech
Grasses
Tim
e, w
arm
ing
>>
Podocarps(bird
dispersed)
Shrubs and small trees(wind, then bird dispersed)
Eastern South Island fire historyFrequency of dates from subfossil charcoals, South Island
(summed in 100-year intervals):
Years before present (BP)
References: McGlone (2001) NZJ Ecol; Rogers, Walker & Lee (2005) Science for Conservation
Frequency
(n =
24
2)
Time
0
5
10
15
20
25
30
30
0 to
4
00
70
0 to
8
00
11
00
to
12
00
15
00
to
16
00
19
00
to
20
00
23
00
to
24
00
27
00
to
28
00
31
00
to
32
00
35
00
to
36
00
39
00
to
40
00
43
00
to
44
00
47
00
to
48
00
51
00
to
52
00
55
00
to
56
00
59
00
to
60
00
63
00
to
64
00
67
00
to
68
00
71
00
to
72
00
75
00
to
76
00
79
00
to
80
00
83
00
to
84
00
87
00
to
88
00
91
00
to
92
00
95
00
to
96
00
99
00
to
10
00
01
03
00
to
10
40
0
Enormous post-
settlement increase in SI
dryland grass pollen percentages
Pre-settlement
Post-settlement
25-75%15-25%10-15%5-10%0-5%
Grass pollen %s in cores
Rogers, Walker & Lee 2005 Science
for Conservation
Grass pollen percentages (same data)
0
20
40
60
80
100
Pre-settlement Post-settlement
Perc
en
tage o
f polle
n s
um
(%
)
Otago sites Canterbury sites
MarlboroughRogers, Walker & Lee
Science for Conservation
Creation of the grasslands
A few tussock species spread far and wide
Those with most rapid growth rates!
enabled by •‘mast’ seeding: periodic massive
seed production•longish (>decades?) fire return
times
Midribbed snow tussock
Red tussock
Narrow-leaved snow
tussock
Slim snow tussock
Lloyd, Lee & Wilson (2002) Conservation
Biology
Gitay, Lee, Allen & Wilson(1992) Journal of Environmental
Management
Recovery following burning
Chionochloa rigida
13 Otago sites with known fire history,
Measurements taken in 1989 at 1 to 26 years since burning
TIME SINCE LAST BURNING>>>
Some characteristics have not fully
recovered in 30 years
New Zealand grasses recover slowly from disturbance
Payton, Lee, Dolby & Mark(1986) NZJ Botany
UNBURNED
New Zealand grasses recover slowly from disturbance
Bracken (for the first time) and scrub on steeper land
•Different stages of recovery from infrequent Maori fires
•Abundance of palatableplants
•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
Transformation of the grasslands
Began with European settlement
Late 19th century over-enthusiasm
“exploitative pastoralism”•More frequent burning•High stocking rates•New plants
The period of pastoralism
O’Connor (1986) TGML Journal
Transformation of the grasslandsChanges 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!
The period of pastoralism
Three synergies in the transformation of the dryland grasslands
1. Burning + grazing2. Domestic + feral grazers 3. Reduced native dominance + exotic invasion
Grazing-only effects:experimental evidence
Chionochloa rigida (narrow-leaved snow tussock)
Carrick Range, Otago
Grazing affects tussock regeneration:
a) reduced overall recruitment
b) reduced proportions small seedlings
c) reduced seedling heightd) reduced proportion of
seedlings distant from plant
small tussocks <- -> large tussocks small tussocks <- -> large tussocks
“LIGHT” grazing(control)
“HEAVY” grazing
Immature 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
Burning + grazing synergy:experimental evidence
Mark (1965) NZJ Botany
0
20
40
60
80
100
Maungatua 870 m Old Man Ra. 1220 m Coronet Peak 1190 m
Mean number of new tillers emerged in the 2 years following spring and autumn fires
Spring Spring Spring
Autumn Autumn Autumn
0
20
40
60
80
100
Maungatua 870 m Old Man Ra. 1220 m Coronet Peak 1190 m0
20
40
60
80
100
Maungatua 870 m Old Man Ra. 1220 m Coronet Peak 1190 m
Burned only Burned and then regrowth
clipped
Synergy 2. Domestic + feral grazers
&V&V &V&V &V &V&V
&V&V
&V
&V
&V &V&V&V
&V
&V&V&V&V&V&V
&V&V
&V&V&V
&V
&V&V&V
&V&V&V&V &V
&V&V&V &V&V&V
&V&V&V&V&V&V&V&V
&V&V&V&V &V&V&V&V&V&V &V
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Ecological Districts&V Towns# Sampling sites
N
Alluvial grassland sites
Survey evidence
957 quadrats in 47 alluvial systems
Walker & Lee (2000; 2002; 2003)
Synergy 3: Reduced native dominance + exotic invasion
0
1
2
3
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Number (n) of exotic plant species >>
Nati
ve d
om
inan
ce
Average native dominance score (for quadrats with n exotic species)
•Fewer exotic species where structural dominance of native species is greater
•Main invaders are perennial forbs and grasses
•Relatively few woody invaders NATIVE EXOTIC
TOTAL FLORA 247 79
ANNUALSDicot (non-grass!) herbs 4 12Grasses 2 6
N-FIXERSHerbaceous 0 7Woody 5 2
PERENNIALSDicot (non-grass!) herbs 116 34*
Grasses 28 14*
Sedges 35 1-
Orchids 5 0-
Trees 35 1-
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, toboom-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 ecologyRadiations and endemism
The rule and role of birds and reptilesAll but fire-free Herbs and wood
3. Humans and the transformation of ecosystemsPost-settlement period
Pastoral period
4. Where to from here?Four trends in drylands today
The case for a return to woody dominanceRetreating opportunities
Trends in dryland landscapes todayIntensive agriculture: complete transformationContinued 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 todayIntensive agriculture: complete transformationContinued 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 todayIntensive agriculture: complete transformationContinued 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 todayIntensive agriculture: complete transformationContinued 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
Monitoring Plots 1992 - 2009
1992
1992
2009
2009
Flat Top Hill Conservation Area, Central Otago(retired & reserved 1993)
2009
Pragmatic dryland conservation goals?
Return to past states is impracticalToday’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 light-demanding
Focus of 8-year FRST-funded ‘dryland’ research programmeFacilitating 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)
0
2000
4000
6000
8000
10000
12000
14000
A B C D E F G H
Dryland type
Are
a (
km2)
Wood
Grass
Intensivelydeveloped
0
10
20
30
40
50
60
70
80
90
100DOC recommended for protection as public land
More developable landMore threatened biodiversity
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
Recommendations and achievements for significant inherent values in Tenure Review to 2007
LINZ achieved protection
% o
f id
en
tifi
ed
sig
nifi
can
t in
here
nt
valu
es
<10% indigenous cover left
10–20% left 20–30% left >30% left and <10%
protected
>30% left and 10–20%
protected
>30% left and >20%
protected
Leases retain more indigenous cover than private land in the same environments
% indigenous cover remaining in environments
Indig
enous
cover
reta
ined (
%)
0 20 40 60 80 100
0
20
40
60
80
100
Private land
Leases
A: 1990 B: 2009
Converted by 1990 Converted by 1990
Converted between 1990 and 2009
Mackenzie Basin floor
B: 2009
Converted by 1990
Converted between 1990 and 2009
Grays Hills
Sawdon
SimonsPass
Glenmore
Mackenzie Basin floor leases
Conclusion
Restoring dryland ecological integrity through woody dominance may be possible
BUT
only if the habitat remains
Thanks!
Ideas, information and photosNick 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)