protecting indigenous biodiversity in the eastern south island rainshadow zone

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

Pastoral period

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

Canterbury dryland environments

THREATENED ENVIRONMENT

Canterbury Region (~2005)

Distribution of threatened plants

% LOSS of indigenous cover since European settlement,

by elevation zone

levati

ically

0 to 400m 400 to 800m 800 to1200m

1200 to1600m

>1600 m

Lowland Montane Subalpine & Alpine

Canterbury’s 103 Acutely and Chronically

Threatened plants(2005 threat classification categories)

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

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

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

A B C D E F G H

Dryland type

WoodyGrassy

Intensivelydeveloped

mixed native-exotic

Pastoral period

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

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

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

3. Humans and the transformation of ecosystemsPost-settlement period – creation of the grasslandsPastoral period – transformation of the grasslands

The arrival of humans

Clarks Junction fossil pollen trends through the Holocene (from McGlone 2001, NZ Jecol)

Grasses

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

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)

Pre-settlement Post-settlement

tage o

f polle

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

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

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

Maungatua 870 m Old Man Ra. 1220 m Coronet Peak 1190 m0

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

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Ecological Districts&V Towns# Sampling sites

Alluvial grassland sites

Survey evidence

957 quadrats in 47 alluvial systems

Walker & Lee (2000; 2002; 2003)

Synergy 3: Reduced native dominance + exotic invasion

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Number (n) of exotic plant species >>

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”

The rule and role of birds and reptilesAll but fire-free Herbs and wood

Pastoral period

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

Expansion of mixed, native-exotic woody vegetation

Tekapo Scientific Reserve, Mackenzie Basin 1992 to 2009

Monitoring Plots 1992 - 2009

Flat Top Hill Conservation Area, Central Otago(retired & reserved 1993)

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)

A B C D E F G H

Dryland type

Intensivelydeveloped

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

<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

ined (

0 20 40 60 80 100

Private land

Leases

A: 1990 B: 2009

Converted by 1990 Converted by 1990

Converted between 1990 and 2009

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

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)

protecting indigenous biodiversity in the eastern south island rainshadow zone

talksouth island drylands

european settlement

indigenous biodiversity

new zealands

drylands todaythe case

kowhai remnants

broadleaved forest

endemismthe rule

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