economic tools in order to answer two fundamental questions: Does the benefit of
slowing or preventing its spread outweigh the costs? What is the most cost
effective method to control the spread?
17.2 Acacia saligna: An Invasive Species
17.2.1 Background
Acacia saligna is a small tree indigenous to Australia and known around the world
as an invasive species owing to its rapid growth rate and ability to competitively
exclude native species (Cohen and Bar (Kutiel) 2004). It was first brought to Israel
by the British in the early part of the twentieth century for forestation, soil conservation, and stabilization of sand dunes to protect roads, agriculture, and settlements (Bar (Kutiel) et al. 2004; Cohen and Bar (Kutiel) 2004). In the early
1960s, the JNF planted A. saligna in the Nizzanim coastal sand dunes as a means
of stabilizing shifting dunes. Acacia saligna has spread quickly into native habitats
by transforming the nature of the soil (such as increasing organic matter and nitrate
content) and the hydrology (such as decreasing water infiltration rate and the
ground water level) to better suit its own ecological needs (Mehta 2000). Likewise,
it out-competes dwarf native plants through shade and an enormous seed bank that
may stay dormant for 50 years (Mehta 2000).
17.2.2 The Impact of Acacia saligna in Israel
The transformation of an organism into an invasive species and its spread is a
stochastic process. ‘‘A species must advance through several stages before being
considered invasive: (1) it must be imported to an area where it is not native; (2) it
must be introduced into the wild; (3) it must become established with a selfsustaining population; (4) it must be a pest which means that it must trigger costs
to humans or ecosystems that outweigh any attendant benefits’’ (Shogren and
Tschirhart 2004, p. 2). Acacia saligna has clearly advanced through stages 1–3
within Israel (Bar (Kutiel) et al. 2004; Cohen and Bar (Kutiel) 2004) and therefore
its invasion is seen as costly to both humans and ecosystems in that country.
The presence of A. saligna in the coastal sand dunes in Israel has a negative effect
on the characteristic native vegetation as well as on the fauna (Cohen and Bar (Kutiel)
2004; Manor et al. 2007). It is obvious mainly at the inter-dune depressions and at the
aeolianites (local type of sandstones), where it is expressed in cover, richness, and
composition. The negative effects of A. saligna on the plant composition (abundance
and richness) are expressed chiefly by reducing the psammophyle species; nearly
100 % of the species in the non-invaded mobile dunes are psammophytes, while less
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D. Lehrer et al.
slowing or preventing its spread outweigh the costs? What is the most cost
effective method to control the spread?
17.2 Acacia saligna: An Invasive Species
17.2.1 Background
Acacia saligna is a small tree indigenous to Australia and known around the world
as an invasive species owing to its rapid growth rate and ability to competitively
exclude native species (Cohen and Bar (Kutiel) 2004). It was first brought to Israel
by the British in the early part of the twentieth century for forestation, soil conservation, and stabilization of sand dunes to protect roads, agriculture, and settlements (Bar (Kutiel) et al. 2004; Cohen and Bar (Kutiel) 2004). In the early
1960s, the JNF planted A. saligna in the Nizzanim coastal sand dunes as a means
of stabilizing shifting dunes. Acacia saligna has spread quickly into native habitats
by transforming the nature of the soil (such as increasing organic matter and nitrate
content) and the hydrology (such as decreasing water infiltration rate and the
ground water level) to better suit its own ecological needs (Mehta 2000). Likewise,
it out-competes dwarf native plants through shade and an enormous seed bank that
may stay dormant for 50 years (Mehta 2000).
17.2.2 The Impact of Acacia saligna in Israel
The transformation of an organism into an invasive species and its spread is a
stochastic process. ‘‘A species must advance through several stages before being
considered invasive: (1) it must be imported to an area where it is not native; (2) it
must be introduced into the wild; (3) it must become established with a selfsustaining population; (4) it must be a pest which means that it must trigger costs
to humans or ecosystems that outweigh any attendant benefits’’ (Shogren and
Tschirhart 2004, p. 2). Acacia saligna has clearly advanced through stages 1–3
within Israel (Bar (Kutiel) et al. 2004; Cohen and Bar (Kutiel) 2004) and therefore
its invasion is seen as costly to both humans and ecosystems in that country.
The presence of A. saligna in the coastal sand dunes in Israel has a negative effect
on the characteristic native vegetation as well as on the fauna (Cohen and Bar (Kutiel)
2004; Manor et al. 2007). It is obvious mainly at the inter-dune depressions and at the
aeolianites (local type of sandstones), where it is expressed in cover, richness, and
composition. The negative effects of A. saligna on the plant composition (abundance
and richness) are expressed chiefly by reducing the psammophyle species; nearly
100 % of the species in the non-invaded mobile dunes are psammophytes, while less
274
D. Lehrer et al.