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The Pacific is biologically unique, because the isolated islands provide ideal
conditions for the development of new species. Birds illustrate the outstanding
biological uniqueness of the region – the Pacific has 15% (408 of 2700)
of the world’s restricted range bird species in only 0.4% of its total
land area.
Many of the unique plants and animals of this region are amongst the most endangered
in the world, mainly because the tiny sizes of most of the islands also means
the total world populations of many of these species are naturally very small,
which makes them very vulnerable to any disturbance. Thus most extinct species
came from islands – similar figures apply to other groups. Pacific currently
has 24% of the world’s threatened bird species and has already lost many
species.
One of the key threats to the remaining species globally and in the Pacific
is land clearing. But on the islands, invasive species pose an even greater
risk to living things.
Invasive species are also known as introduced species or pest species, sometimes
called invasive alien species. They are species living where they do not belong.
Invasive species are highly adaptable and usually widespread. They can live
in a wide range of environments. They breed fast and spread easily. When they
arrive in a new country, they have usually left the diseases and predators
that would have kept their numbers under control back in their home country.
The brown tree snake was introduced to Guam accidentally in the late 1940s.
Its introduction has resulted in ecological devastation, including the permanent
loss of nine of the eleven original native bird species in Guam, along with
five species of lizard. There are an estimated 80 million brown tree snakes
on Guam today, and they cause damage to electrical infrastructure, causing
power outages every 4 –5 days, damage to household electrical appliances,
and research and control costs totalling over $US 5 million a year in Guam
alone. This does not include the costs to Guam’s major trading partners
to ensure that snakes that hitchhike in goods or on aircraft or ships from
Guam are detected before they can establish new populations. They also impact
on health - their bites pose a risk especially to children.
Invasive vines like merremia and mikania vines smother forest canopies, reducing
the production of flowers and fruits that fruit bats and native birds such
as pigeons depend on. They are also close to the top of regional agricultural
weed lists.
Invasive species can come from any group of living things like insects such
as ants. Rats have some of the biggest impacts. There are also invasive birds
such as the mynah and aquatic species, both freshwater and marine species.
These are just a few examples.
Invasive species have a range of effects on the environment and on humans:
They threaten many species with extinction. They interfere with the species
that make up ecosystems and change the way they function. They have negative
impacts on the resources people rely on to live – food, clean water,
and shelter. They carry diseases and can directly harm humans. They can impact
on species we rely on for our livelihoods, or can reduce the tourist potential
of the area by reducing the reasons they want to visit and they can impact
on Pacific islanders traditional activities.
90% of species that have become extinct since 1800 were island birds, and 90%
of these have fallen victim to an invasive species. Many endemic bird species
are in trouble in the Pacific, some directly threatened by predators such as
rats and stoats, whilst others are threatened by loss of habitat and food due
to smothering of their forests by introduced vines.
Ship rats are one of the biggest threats to the survival of birds of the region – they
eat eggs and young birds, especially of ground breeding species. They recently
arrived in Kiribati’s Christmas Island, which was formerly the largest
seabird breeding colony in the world – 18 species of seabird were seen
in numbers of up to 6 million.
Meanwhile over in the Indian Ocean’s Christmas Island, which was famous
for its red land crabs, the crazy ant developed huge super colonies that covered
the ground and killed all the red land crabs in its path, although, millions
of dollars later, it is hoped to be under control.
An example of the impact invasives can have on the economic sector. In Samoa
a decade ago an outbreak of taro leaf blight, a fungal disease, decimated taro
production, which formed a key part of the Samoan economy. It is estimated
to have cost Samoa more than the impact of three cyclones, $US 40 million,
to replace domestic consumption, lost exports and the cost of measures to control
the disease.
Regardless of where we live, invasive species can impact on us all. Every country
of the Pacific has invasive species that cause problems and is at risk of getting
new ones. Prevention is definitely better than the cure.
Some invasives were introduced deliberately by people as a food source. Biological
control can be an effective method to control certain invasive species, but
if not carefully checked first, the biological control agents can become invasive
themselves.
Pacific islanders are great gardeners. A large proportion of plant invaders
were originally legally introduced for ornamental purposes. Pacific gardeners
also often smuggle in garden plants – often as seeds – and produce
for their own use. Plant pests, ants and diseases have been introduced as contaminants
of fruits, vegetables, soil, plants and commercial feed.
The rate of accidental introductions is increasing as there is more movement
of people and more and freer trade around the region. Quarantine often exists
at the international borders of countries but not between islands within the
country, so increased people movement increases the risk of invasion substantially.
Containers and packaging materials also pose a risk. Invasive species can hitchhike
to new islands in many ways – they can be transported in cargo and household
goods, in cars or timber, in military equipment or used machinery, and in personal
effects such as hiking boots and camping equipment.
Shipping is a particular risk as it is more likely to visit uninhabited islands.
Yachts pose a risk in the Pacific. Over 2000 yachts visit the Vavau islands
of Tonga each year. Invasive species can be found in the ballast water of ships
or clinging to the their hulls.
There are five steps that can be taken depending on the invasive situation:
Prevent invasives getting to each island
Detect them quickly if they do
Respond rapidly to the incursion
Control the population
Eradicate the species from the island
The Pacific is a leader in collaborating to address invasive species, The regional
invasive species strategy, developed collaboratively by countries and endorsed
by them all in 2000, was the first regional strategy of its kind in the world
and provides a framework for efforts to increase country capacity to take the
five steps in relation to invasive species, particularly emphasising prevention.
This essay was written by Liz Dovey, Bird Conservation and Invasive Species
Officer, SPREP
Go to "Bird Conservation and Invasive
Species" page