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

tim.reynolds@sa.gov.au