A r u n d o d o n a x A r u n d o d o n a x Spanish Reed Spanish Reed Arundo donax Arundo donax : : Economic implications and Economic implications and Ecological realities of a Ecological realities of a riparian invader species riparian invader species Richard Knight Richard Knight, Botany, Department, University of the Western Cape, South Africa Gretchen Coffman Gretchen Coffman, Department of Environmental Health Sciences University of California, Los Angeles UCLA, United States Edited by: Jeff Manuel, Department of Biodiversity and Conservation Biology, University of the Western Cape, South Africa.
Economic implications and Economic implications and Ecological realities of a riparian Ecological realities of a riparian
invader speciesinvader species
Richard KnightRichard Knight, Botany, Department, University of the Western Cape, South Africa
Gretchen CoffmanGretchen Coffman, Department of Environmental Health Sciences University of California, Los Angeles UCLA, United States
Edited by: Jeff Manuel, Department of Biodiversity and Conservation Biology, University of the Western Cape, South Africa.
Aru
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Aru
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ax •Arundo donax Arundo donax is a perennial grass is a perennial grass
species that superficially species that superficially resembles bamboo and forms resembles bamboo and forms dense stands in riverine areas.dense stands in riverine areas.
Aru
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Aru
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ax •It can grow at a daily rate of 6.5 It can grow at a daily rate of 6.5
cm/day for 40 days and reach 8 cm/day for 40 days and reach 8 meters in a single growing season!meters in a single growing season!
Aru
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Aru
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and warm and warm temperate temperate distribution and distribution and originally originally appears to have appears to have come from India.come from India.
Aru
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Aru
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has been questioned but it appears has been questioned but it appears to have been in the Mediterranean to have been in the Mediterranean basin for many thousands of basin for many thousands of years. years.
Aru
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Aru
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construction in 5000 BC and it was construction in 5000 BC and it was also made into musical pipes by also made into musical pipes by the Egyptians (3000 BC). the Egyptians (3000 BC).
Aru
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Aru
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ax In the Gouritz river catchment, it In the Gouritz river catchment, it
was extensively used for building was extensively used for building warehouse-sheds for tobacco warehouse-sheds for tobacco drying during the last centurydrying during the last century
Aru
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Aru
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Gouritz River Catchment today, Gouritz River Catchment today, indicating it is possibly a livelyhood indicating it is possibly a livelyhood supporting resource.supporting resource.
Aru
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Aru
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concern are concern are the well the well developed developed undergroununderground rhizomes d rhizomes that have that have been been formed.formed.
Aru
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Aru
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ax Its root system reaches a depth of Its root system reaches a depth of
5 meters below the lower rhizome 5 meters below the lower rhizome levellevel
Aru
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Aru
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growth uses growth uses copious copious quantities of quantities of water. water.
•In California, it In California, it uses more than uses more than three times the three times the water of water of indigenous indigenous reeds.reeds. Calitzdorp, RSA
Aru
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Aru
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recharge and interfere with surface recharge and interfere with surface water flow leading to river water flow leading to river channelisationchannelisation
Aru
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Aru
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ground- and surface water ground- and surface water interactions and associated interactions and associated ecological process is as yet ecological process is as yet unknown.unknown.
Aru
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Aru
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ax Since it restricts water flow it will Since it restricts water flow it will
have a major impact on increasing have a major impact on increasing flood risks.flood risks.
Infested Disa River in Flood
Aru
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Aru
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ax By restricting the flow and By restricting the flow and
increasing floods Spanish Reed is increasing floods Spanish Reed is able to spread downstream and able to spread downstream and colonize new areas.colonize new areas.
Aru
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Aru
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compete native compete native Phragmites Phragmites and and most other riparian vegetation.most other riparian vegetation.
Aru
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Once it Once it becomes becomes dominant dominant different different habitats habitats formed by formed by the natural the natural braiding of braiding of the stream the stream are lost.are lost.
Aru
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Aru
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growth totally growth totally shades the shades the stream, lowering stream, lowering water water temperature, temperature, affecting water affecting water oxygen levelsoxygen levels
Aru
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Aru
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channel, effectively preventing channel, effectively preventing almost all meaningful ecological almost all meaningful ecological interactions from occuring.interactions from occuring.
Aru
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Aru
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possesses possesses more biomass more biomass than indigenous than indigenous reeds it reeds it significantly significantly increases fire increases fire risks. risks.
Aru
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Aru
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tightly packed it virtually tightly packed it virtually eliminates feeding and nesting eliminates feeding and nesting sites for birds . sites for birds .
Threatened Least Bell’s Vireo
Aru
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Aru
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to 97% of riverine habitats in to 97% of riverine habitats in California and reduced overall California and reduced overall wildlife value to virtually zero.wildlife value to virtually zero.
Aru
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Aru
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have confirmed that Spanish Reed is have confirmed that Spanish Reed is likely to be initiating a likely to be initiating a trophic trophic cascadecascade of species loss such as of species loss such as has occurred in California! has occurred in California!
Willow Flycatcher
Aru
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Aru
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problem in South Africa?problem in South Africa?
• Declared a class 1 invasive Declared a class 1 invasive speciesspecies
Conservation of Agricultural Conservation of Agricultural Resources Act, Act 43 of 1983)Resources Act, Act 43 of 1983)
Aru
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Aru
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its biology in South Africa?its biology in South Africa?
Henderson 2001
Aru
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Aru
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concentrated our research into concentrated our research into woody invasive aliens!woody invasive aliens!
Aru
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Aru
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& grass species can represent & grass species can represent significant ecological implications significant ecological implications but it has been argued that “very but it has been argued that “very few have caused real damage” few have caused real damage”
(Richardson et al. 2000).
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• One problem One problem is that it has is that it has been around for been around for so long and so long and been used so been used so extensively that extensively that most people most people consider it to consider it to be indigenous! be indigenous!
Aru
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Aru
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with native with native PhragmitesPhragmites sp. when sp. when it is small! it is small!
Where in the Southwestern Cape Where in the Southwestern Cape does Spanish Reed occur?does Spanish Reed occur?
Almost the entire SW Cape!
Aru
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Aru
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Reed occur?Reed occur?
Can occur in almost any part of the
Country!
Aru
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Aru
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Richtersveld (on the Orange River) Richtersveld (on the Orange River) to the moist subtropical areas of to the moist subtropical areas of KwaZulu Natal!KwaZulu Natal!
Aru
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Aru
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potential to be more economically potential to be more economically and ecological damaging that any and ecological damaging that any woody alien species! woody alien species!
