Paper · 2026 · Biocontrol Science and Technology

An assessment of changes in the abundance of two Australian Acacia species under biological control in the Southwestern Cape region, South Africa

C. Marais; J. Hoffmann; M. Powell; et al.

5
claims
9
verbatim quotes
1
citations
3
research areas
—
Not open access

Abstract

Considerable investments have been made in the biological control of invasive Australian Acacia species in the Fynbos biome of South Africa. The biological control agents introduced for the most invasive Acacia species do not kill standing trees but rather reduce the reproductive output, thereby reducing the rate of spread. Here, we consider the changes in the abundance of Acacia saligna (Labill.) H. L. Wendl. and Acacia cyclops A. Cunn. ex G. Don., in the presence of biological control agents for the purpose of informing long-term decision-making on the costs of manual control. We used remote sensing of permanent monitoring plots to assess the impacts of biological control in combination with fire and firewood removal. The cover of these two species where the plots had been left to biological control, informal firewood harvesting, and fire with no other forms of prescribed control for a 20-year period was assessed. The cover decreased by up to 85%, with smaller changes over periods of less than 10 years, and no impacts over a 6-year period. Biological control resulted in a marked slowing down in the rate of increase of the Acacia spp. cover. The reduction in the rate of spread of these two highly invasive species due to biological control should reduce the cost of clearing and, therefore, the financial burden on landowners and natural resource management entities involved in Acacia spp. control.

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Claims 5

Observationobservedoriginal resultpositivemeasured

Claim · model-written summary

Cover of the two Acacia species declined by up to 85% over 20 years under biological control, firewood harvesting and fire.

Taxon
Acacia speciesAcaciat0
Outcome
covere0
Direction
decreasede0
Value
up to 85%e0
Qualifier
20-year periode1

Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Acacia
Acacia · Taxon · picture from its Wikimedia Commons categoryGiles Laurent · CC BY-SA 4.0 · Wikimedia Commons ↗

Verbatim

e0

“The cover decreased by up to 85%, with smaller changes over periods of less than 10 years, and no impacts over a 6-year period.”

✓ located verbatim in the source · abstract, characters 930–1057 · show in text ↑
e1

“The cover of these two species where the plots had been left to biological control, informal firewood harvesting, and fire with no other forms of prescribed control for a 20-year period was assessed.”

✓ located verbatim in the source · abstract, characters 730–929 · show in text ↑
t0

“Acacia species”

✓ located verbatim in the source · title, characters 60–74 · show in text ↑
Observationobservedoriginal resultmeasured

Claim · model-written summary

Acacia cover changes were smaller over periods shorter than 10 years.

Taxon
Acacia speciesAcaciat0
Outcome
changese0
Direction
smallere0
Qualifier
periods of less than 10 yearse0

Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Acacia
Acacia · Taxon · picture from its Wikimedia Commons categoryGiles Laurent · CC BY-SA 4.0 · Wikimedia Commons ↗

Verbatim

e0

“smaller changes over periods of less than 10 years”

✓ located verbatim in the source · abstract, characters 969–1019 · show in text ↑
t0

“Acacia species”

✓ located verbatim in the source · title, characters 60–74 · show in text ↑
Observationobservedoriginal resultno effectmeasured

Claim · model-written summary

No cover impact was observed over six years.

Taxon
Acacia speciesAcaciat0
Outcome
impactse0
Direction
no impactse0
Qualifier
6-year periode0

Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Acacia
Acacia · Taxon · picture from its Wikimedia Commons categoryGiles Laurent · CC BY-SA 4.0 · Wikimedia Commons ↗

Verbatim

e0

“no impacts over a 6-year period”

✓ located verbatim in the source · abstract, characters 1025–1056 · show in text ↑
t0

“Acacia species”

✓ located verbatim in the source · title, characters 60–74 · show in text ↑
Intervention effectobservedoriginal resultpositivemeasured

Claim · model-written summary

Biological control markedly slowed the increase in Acacia cover.

Taxon
Acacia spp.Acaciae0
Treatment
Biological controle0
Outcome
rate of increase of the Acacia spp. covere0
Direction
slowing downe0

Not reportedComparator

Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Acacia
Acacia · Taxon · picture from its Wikimedia Commons categoryGiles Laurent · CC BY-SA 4.0 · Wikimedia Commons ↗

Verbatim

e0

“Biological control resulted in a marked slowing down in the rate of increase of the Acacia spp. cover.”

✓ located verbatim in the source · abstract, characters 1058–1160 · show in text ↑
Recommendationauthor interpretationoriginal resultpositivebasis n/a

Claim · model-written summary

The authors expect biological control to reduce clearing costs and financial burden.

Taxon
Acacia spp.Acaciae0
Treatment
biological controle0
Outcome
cost of clearing and, therefore, the financial burdene0

Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Acacia
Acacia · Taxon · picture from its Wikimedia Commons categoryGiles Laurent · CC BY-SA 4.0 · Wikimedia Commons ↗

Verbatim

e0

“The reduction in the rate of spread of these two highly invasive species due to biological control should reduce the cost of clearing and, therefore, the financial burden on landowners and natural resource management entities involved in Acacia spp. control.”

✓ located verbatim in the source · abstract, characters 1161–1419 · show in text ↑