Box 11.3 (continued)
Liquidambar (Liquidambar styraciflua), Plane Trees (Platanus species), oaks
(Quercus species), willows (native and alien Salix species), native coral trees
(Erythrina species) and bushwillows (Combretum species) have been found to
be susceptible reproductive hosts and stand to be lost from the urban landscape. Besides its impact in the urban environment, PSHB poses a threat to
many economically important tree crops including Pecan Nut (Carya
illinoinensis) and Avocado (Persea americana), plantations of Australian
Acacia species, and to natural ecosystems.
The full extent of PSHB impact on the South African urban environment
will only be ascertained over time. Municipalities already face the costly
removal of many heavily infested street trees. This loss will have a profound
impact on urban biodiversity and ecosystem services and result in reduced
amelioration of the urban heat-island effect. Besides the financial burden of
tree removal there are losses associated with reduced residential property
values, and in the longer-term municipalities will also bear the cost of tree
replanting.
South African municipalities have never had to deal with a tree-killing
pest of this magnitude before (unlike cities in North America, Europe, and
Australasia). With limited resources available, a coordinated and strategic
response has been slow to emerge. Without prioritisation of removal of
reproductive host trees and disposal at designated dumping sites (by chipping
and composting or solarisation), the unintentional dispersal of PSHB (potentially over great distances) through the movement of infested wood sold as
firewood is inevitable. Therefore, the situation requires a consolidated strategy
and action plan, with input from research, engagement with stakeholders, and
guidance from national government departments with a strong focus on
effective communication and awareness campaigns.
11.4 Management
The Alien and Invasive Species regulations promulgated under the NEM:BA places
a ‘Duty of Care’ on all landowners, whether private or public, to control invasive
species on their land. This legislation requires all ‘Organs of State’ at all spheres of
government (from national through to local government) to compile invasive species
monitoring, control and eradication plans for land under their control. However,
such “organs of state” face multiple challenges which makes compliance with the
NEM:BA regulations difficult (Irlich et al. 2017).
Urban ecosystems present a new set of challenges relating to the understanding
and management of biological invasions, and there is an urgent need for greater
exploration of invasion processes and impacts in urban areas (Gaertner et al. 2017a,
b; Irlich et al. 2017). Arguments for and against managing invasive species in urban
11 Biological Invasions in South Africa’s Urban Ecosystems
297
Liquidambar (Liquidambar styraciflua), Plane Trees (Platanus species), oaks
(Quercus species), willows (native and alien Salix species), native coral trees
(Erythrina species) and bushwillows (Combretum species) have been found to
be susceptible reproductive hosts and stand to be lost from the urban landscape. Besides its impact in the urban environment, PSHB poses a threat to
many economically important tree crops including Pecan Nut (Carya
illinoinensis) and Avocado (Persea americana), plantations of Australian
Acacia species, and to natural ecosystems.
The full extent of PSHB impact on the South African urban environment
will only be ascertained over time. Municipalities already face the costly
removal of many heavily infested street trees. This loss will have a profound
impact on urban biodiversity and ecosystem services and result in reduced
amelioration of the urban heat-island effect. Besides the financial burden of
tree removal there are losses associated with reduced residential property
values, and in the longer-term municipalities will also bear the cost of tree
replanting.
South African municipalities have never had to deal with a tree-killing
pest of this magnitude before (unlike cities in North America, Europe, and
Australasia). With limited resources available, a coordinated and strategic
response has been slow to emerge. Without prioritisation of removal of
reproductive host trees and disposal at designated dumping sites (by chipping
and composting or solarisation), the unintentional dispersal of PSHB (potentially over great distances) through the movement of infested wood sold as
firewood is inevitable. Therefore, the situation requires a consolidated strategy
and action plan, with input from research, engagement with stakeholders, and
guidance from national government departments with a strong focus on
effective communication and awareness campaigns.
11.4 Management
The Alien and Invasive Species regulations promulgated under the NEM:BA places
a ‘Duty of Care’ on all landowners, whether private or public, to control invasive
species on their land. This legislation requires all ‘Organs of State’ at all spheres of
government (from national through to local government) to compile invasive species
monitoring, control and eradication plans for land under their control. However,
such “organs of state” face multiple challenges which makes compliance with the
NEM:BA regulations difficult (Irlich et al. 2017).
Urban ecosystems present a new set of challenges relating to the understanding
and management of biological invasions, and there is an urgent need for greater
exploration of invasion processes and impacts in urban areas (Gaertner et al. 2017a,
b; Irlich et al. 2017). Arguments for and against managing invasive species in urban
11 Biological Invasions in South Africa’s Urban Ecosystems
297