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Buffel Grass in SA Meeting the challenge
Tim Reynolds
13 Sept 2012
Presentation overview
• Threat posed by buffel in SA
• What can we achieve in SA?
• A plan of action for the State
Buffel grass is also an
unwanted invasive
species in climatically
similar parts of the USA
Some challenges in SA
• Buffel is widespread (present in most regions)
• It is locally abundant (eg far North-west)
• It is not yet declared for control under legislation
• It is a contentious species (fodder species vs serious pest)
Photo: R Davies
Defining the risk of buffel grass in SA
State-level Weed Risk Assessment* (Landuse: arid/ semi-arid rangelands)
Weed risk .........................................VERY HIGH
Feasibility of containment.........................HIGH
State-level Management Response.........DESTROY INFESTATIONS
* SA Weed Risk Management System
Buffel grass is arguably the
single greatest threat to biodiversity by an invasive species
in the State‟s vast arid region
Buffel grass is also a serious fire threat to remote
communities...
Controlled buffel grass burn-off
to reduce wildfire risk,
AW NRM Region, 2010
Buffel grass can also degrade and replace
valuable native pastures
Photo: J Read, April 2012 Monoculture of Buffel grass, Kalka, APY Lands
PROFILE of Buffel Grass
• Environmentally, buffel grass is considered one of Australia‟s
worst weeds (Humphries et al. 1991)
• It is arguably the most successful introduced pasture grass in
northern Australia
• It has been identified as a „transformer weed‟ of the Australian
rangelands (Bastin et al. 2008)
• Modelling indicates it could establish in over 60% of mainland
Australia (Lawson et al. 1994)
Transformer Weeds are the most damaging invasive plant
taxa within given regions, or globally. This term refers to a
subset of invasive plants which „change the character,
condition, form or nature of a natural ecosystem over
a substantial area‟.
It is these species, comprising perhaps only about 10% of
invasive species, that have profound effects on
biodiversity and that clearly demand a major allocation
of resources for containment /control/eradication.
What is a “Transformer Weed”?
It is a good opportunist - it can survive
extended dry periods well, but when growing
conditions improve (i.e. summer rainfall) it has
the ability to spread rapidly and aggressively
invade new habitats.
Why is buffel grass a successful weed
in arid environments?
The success of Buffel grass in arid environments is due to
the following biological attributes:
• A deep root system (up to 2.5m)
• Tussocks are long-lived (>20 yrs)
• Rapid growth rate, and fast maturation - seed germination to seed
production in as little as 4-6 wks
• Prolific seed production
• Soil seed persistence may be greater than 4 or 5 years
• High seed dispersal ability
Also...
Arid environments present less competition, disease and predation
CURRENT DISTRIBUTION IN SA
• Buffel grass is widespread across the State (it occurs in 6 NRM
Regions)
• Some parts of the State have been extensively invaded by buffel
(e.g. the arid far North-west)
• There are other arid regions of the State where buffel is largely
absent (e.g. the Great Victoria Desert)
POTENTIAL DISTRIBUTION IN SA
• Over 75% of South Australia is arid
• Buffel grass is climatically well suited to becoming established
over much of the State‟s arid region
• Buffel grass is yet to reach the full limits of its potential
distribution
Climatic modelling - SA
Human-assisted dispersal is a major factor
in the spread of buffel grass
Photo: Sheldon Navie
DISPERSAL
Buffel grass reproduces mainly by seed. The seeds
are dispersed in soft burr-like structures & are easily
blown about by the wind. They may also float on
water & readily become attached to livestock, other
animals, clothing, machinery &vehicles
Livestock transport
Long distance dispersal can occur in contaminated agricultural produce (e.g. pasture seeds, gain and wool).
Watercourses
Photo: Ben Shepherd
Under favourable
seasonal conditions
Buffel grass may
spread readily and
aggressively invade
arid riparian areas.
Roads and tracks
Photo: R Davies 2003, APY Lands
Photo: D Powell
Seeds are commonly introduced into new
areas along roads and tracks. Spread along
roads is assisted by vehicle draughts and
movement of soil by graders and other
machinery and vehicles.
From the road or track verge buffel
grass then spreads into the
surrounding vegetation by wind or
water, with drainage lines acting as
conduits for more distant dispersal
(Puckley and Albrecht 2004).
Importation of new varieties & plant breeding
– Over 580 accessions of buffel have been brought to
Australia from 35 countries
– the new hybridised „varieties‟ may be better adapted
to local conditions, perhaps with increased climatic
tolerance and disease resistance
This contributes to the ongoing invasion pressure of buffel grass from pastoral production areas into other environments in Australia
Impacts
of buffel grass
Fire: The most damaging act of buffel invasion
is alteration to natural fire regimes
Buffel grass:
– produces fuel loads up to 4-5 times greater than natural fuel loads
– leads to more frequent and intense fires
– significantly increases fire risk by replacing native plants (eg
chenopods) that are not well adapted to fire
– initiates a “positive fire invasion feedback” - buffel invasion is helped
by fires, regenerating quicker than many native species, thereby leading
to extensive infestations
Fire is a fundamental component
of the ecology of arid Australia
• Species that do not tolerate frequent intense fire are typically „long-
lived obligate seeders‟
• These are slow to reach reproductive maturity (1-2 decades) and
typically do not resprout when burnt
• They are disadvantaged when fire recurs before a new generation
has matured and set seed
• Shrublands and low woodlands of obligate seeder species, with
little or no spinifex (fire-prone), are widespread across central arid
Australia
• Acacia woodlands (e.g. mulga) are the most extensive of these,
occupying about a quarter of arid Australia
Fire sensitive communities
Intervals between fires influences the perpetuation of
vegetation types
Veg-habitat type Average fire frequency
Spinifex dunes and swales High (5-30 years)
Chenopod shrublands Low
Riparian woodlands/shrublands Moderate-High
Mulga plains & dune swales Low-Moderate (15-50+ years)
A reduction in the fire-free interval can result in a decline of
the key component species.
Fire-sensitive ecosystems
NLWRA 2001, http/www.nlwra.gov.au
Photo
s: D
EW
NR
1975 fire scar: Effect of fire on mulga / chenopod shrubland
Low open mulga woodland over pearl bluebush (foreground)
1990: Ephemeral herbs with scattered shrubs (bluebush absent;
note dead mulgas in background).
UNBURNT
15 years after fire 37 years after fire
Still little recovery – mainly ephemeral herbs with scattered shrubs
(note dead mulgas & browsed bullock bush in background).
Fire-sensitive ecosystems
NLWRA 2001, http/www.nlwra.gov.au
Buffel grass:
“A major threat to Country” NRM Plan for the Alinytjara Wilurara NRM Region (2011)
Anangu no longer visit areas infested with „Mamu grass‟
(devil‟s grass) because they cannot see tracks or
snakes and kangaroos and bush tucker no longer live
there
Invaded habitats - APY lands
Photos: John Read, April 2012
creekline dune
rocky hill & acacia plain monoculture, sandy plain
Key habitats in need of protection - APY Lands P
ho
to: R
Davie
s, 2
00
3
An almost pristine Arid Native Grassland, save for a
solitary buffel grass plant only metres from a road!
Species at risk (examples)
Black-footed rock-wallaby / Warru
Buffel grass promotes hot
wildfires which can destroy
fire sensitive vegetation on
which warru rely, such as
Figs (Ficus) and Spearbush
(Pandorea sp.).
Photo: Bronwyn Dutch
Wrinkled Honey-myrtle Melaleuca fulgens subsp. corrugata
http://bie.ala.org.au
Photo: Ivan Holliday
Capable of resprouting after occasional fires, local extinction of this species has been
observed after a series of three fires in 30 years. It currently has a highly fragmented
distribution across the Central Ranges bioregion, occurring only at one or two sites on
the highest peaks of the various range systems. Its total area of occupancy is thought
to be less than 5 km2.
Is SA better placed than other States to deal with
the Buffel grass threat?
• Pastoral Board policy prevents introduction of non-indigenous species
• The use of buffel as a forage species has not been promoted by SA govt.
agencies
• The views of pastoral and conservation interests in SA are less polarised
than in other States (e.g. NT, Qld) where progress toward policy
development and strategic management of environmental impacts at
broad scales is prevented (e.g. Friedel et al.)
• Soils and climate are probably less suitable for buffel than other regions
of Australia, so historically there has been less incentive to use it as a
pasture species – but there is a high potential for greater range
expansion in SA
• At least 5 NRM Boards have already identified it as a priority pest
species and are actively controlling it
• There remains the potential to eradicate and prevent the establishment
of buffel over a significant proportion of the State
Unlike other Australian States with extensive arid
rangelands, SA has an opportunity now to
prevent buffel grass from becoming permanently
established across a significant portion of this
important biome
A strategic plan for
South Australia
VISION:
Buffel grass is contained and its impact
reduced to a minimum in South Australia
SLIDE HEADING Regular text to be inserted
Zone 1 – Manage
Zone 2 – Contain
spread
Zone 3 – Destroy
infestations
STATE MANAGEMENT ZONES
GOALS
GOAL 1 – PREVENT (all Zones)
Exclude the entry of buffel grass into SA and prevent its movement within the State
GOAL 2 – MANAGE impacts of buffel grass in ZONE 1
Reduce the overall impacts of buffel grass through targeted management
GOAL 3
CONTAIN SPREAD of buffel grass in ZONE 2 Prevent the ongoing spread of buffel grass aiming for a significant reduction in all infestations
DESTROY infestations in ZONE 3 Significantly reduce the extent of buffel, locating & destroying all infestations aiming for local eradication
where feasible
GOAL 4 - BUILD CAPACITY (all Zones) Ensure SA has the capability and commitment to manage buffel grass
Linkages with other plans
Buffel grass
State Strategic Plan
NRM District Weed Strategy (multi-species)
NRM District Operational Plan
(Buffel grass)
State Policy
Expected outcomes
• A greater understanding & awareness of the threat posed by
buffel grass in SA
• A better understanding of its biology, environmental preferences
and control
• Greater engagement in prevention & control of buffel grass by
all stakeholders
• The capacity and resources to act when needed (the enemy
won‟t wait for us!)
• Containment lines established and priority infestations
destroyed
State Taskforce
A State buffel grass taskforce is proposed. Its role is to coordinate &
oversee the implementation of the Strategic Plan, ie to:
• Maintain and build partnerships with key stakeholders
• Identify funding sources and provide independent advice
• Coordinate the exchange of information on distribution and control
• Implement monitoring and reporting protocols
• Assist in developing and implementing programs and initiatives
• Develop and implement communication and extension plans
Knowledge gaps
• Habitat preferences – invasion vs est. vs spread
• Seed bank longevity
• Fire ecology – differences between habitats
• Impacts on biodiversity eg spp at risk, effect on ecosystem
structure & function
• Taxonomy
• Mgt/control – eg fire as a component of integrated control
• Distribution modelling – eg spatial or habitat modelling at a
range of spatial scales
Knowledge gaps and directions for future investigation and
research in South Australia:
Next steps?
• Finalise & release Strategy
• Form a State Taskforce
• Seek declaration under NRM Act
• Facilitate the inclusion of strategic buffel grass management in
regional and local plans
• Seek funding opportunities
Acknowledgements
Ben Shepherd (RSSA)
Kate Reid (RSSA)
Annmarie Mabarrack (RSSA)
John Read (Ecological Horizons)
Victoria Marshall (Univ. Adelaide)
Trevor Hobbs (DENR)
Gavin Baird (DENR)
Augie Facelli (DENR)
Rick Davies (Outback Ecology)
David Powell (DPTI)
Contact
Tim Reynolds
Biosecurity SA
ph 8303 9501