Download Benefiting from the modern transit, people today can easily travel

Benefiting from the modern transit, people
today can easily travel to almost any place
on this planet. However, trouble-free
transportation also gives a rise to the
invasion of imported foreign species. So far,
reports have it that imported species usually
won’t come in alone: they also bring some
negative effects to the host lands.
First, some local species can be replaced by
newly imported ones and even because
extinct under extreme circumstances. This
danger emerges mostly riskily in ecological
systems that are traditionally isolated from
the others. For example, Australia can be
one best showcase because the native
Australian species are generally considered
less competitive in the contest for natural
resources, compared with introduced
species from other continents.
Second, new species also bring dangers to
the local ecological system sometimes. For
example, cane toad, a species that recently
brought into South America from West
Africa, has been believed to be responsible
for hundreds of poisoning accidents. This is
because neither South American people nor
native animals have any previous knowledge
about this toxic toad and dangers happen
once they fail to keep distance away from it.
Third, newly introduce species can be
economic burden to the local people as well,
if not properly handled. For instance, the
mesquite tree encounters few natural
enemies and spreads rapidly right after its
introduction into Africa. Failing to compete
with mesquite trees for sunshine and water
resource, many local economical plants die
off and this is also followed by great
reduction in agricultural output.
In the lecture, the professor makes several
points to demonstrate cases in the passage
does not always happen and imported
species may be a bliss to local people/
Firstly, in agriculture, it is proved that
competitive foreign plants are better
substitute of local plants. She then further
explains her point by giving an example of
maize. He said that maize was not
introduced to Asia until recently. But Asian
farmers loved maize as soon as they got to
know it for maize survive many rigorous
environments while local crops need
constant care. So even if local species are
replaced by newly imported species as the
passage concerned, there will not be such a
big negative effect.
Secondly, after imported species blend into
new environment, they will no longer be
dangerous to local people and animals. The
cane toad does poison people and native
animals but they live peacefully in Florida
since the local people find out cane toad
eats a lot of local pests like flyers and
mosquitoes.
Thirdly, newly introduce species are not
necessarily economic burden to the local
people. The professor argues that imported
species will bring out positive effects to the
host country. Admittedly mesquite trees
may cut off light and water resources of
local economical plants and cause
agriculture output reduction. But the
mesquite tree is a precious recourse as
firewood for it grows fast, lives short and
perfect for burning. Thus, introduced
species also benefit the local economics.