(JP)Impact of (wittingly or unwittingly) introducing alien species to ecosystems

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http://www.japantimes.co.jp/cgi-bin/getarticle.pl5?fl20010930a7.htm

 

Impact of (wittingly or unwittingly) introducing alien

species to ecosystems

Alien invaders

 

By MARK BRAZIL

Special to The Japan Times

 

They arrive in bunches of bananas; they turn up in

containers of vegetables; they sneak in hidden inside

rattan and wooden furniture; they disembark from among

shipped household possessions, industrial and military

equipment. They are as pervasive as the computer

server virus Nimda, but, in their own way, far more

destructive.

 

What are they? Not illegal immigrants but aliens

nonetheless -- and seemingly Japan has no laws for

restricting either their arrival or their dispersal.

 

These aliens are capable of withstanding chilling;

gassing; changes of pressure; and lack of both water

and food for prolonged periods. They are the most

successful living creatures on Earth: They are

insects.

 

Alien or introduced species, those " imported " from

outside their natural range into a country

unaccustomed and ill-equipped to cope with them,

perhaps represent the greatest environmental threat

after habitat loss. Accidental introductions are

problematic enough, but the deliberate introduction of

species is tantamount to ecoterrorism, with

potentially catastrophic results.

 

Introduced mammals, birds, fish, reptiles and

amphibians can wreak havoc with ecosystems in a

delicate equilibrium, but at least the larger of them

are noticeable: black bass in Lake Biwa, mongooses in

the Nansei Shoto, raccoon in Hokkaido. But who notices

alien insects? Who, even, can identify them?

 

Japan's insect biodiversity is so great that there are

few specialists capable of recognizing the new

invaders. Discovery of a new species poses a

conundrum: Is the creature a native species merely

overlooked in the past, or a newly arrived alien? Only

investigations by experts in a particular taxonomic

field may provide the answer.

 

But how grave is the problem? One moth here, a

mosquito there, the odd beetle or spider -- do they

really matter?

 

For many species, one egg-laden female is all it takes

to launch a new population of potential agricultural,

forestry or social pests. Surely, the arrival of the

western large bumblebee in Hokkaido can't be a

problem?

 

Wrong. A competitor for nectar, it is displacing local

bumblebees that ultimately lose out in the competition

for survival. Not having co-evolved with native

flowers, the differently proportioned mouthparts of

the invaders enable them to take the plants' nectar

without providing that most crucial of services,

pollination, in return. As their rates of pollination

decline, so too does the reproductive success of the

plants; gradually they will lose ground and become

extinct in turn.

 

Introduced beetles can play havoc with natural forest

cover and forest industries, as has been discovered to

considerable cost in the United States and Britain.

Introduced bee mites can devastate honey industries

(as in the North Island of New Zealand). Alien ants,

such as the South American fire ant that has reached

the Galapagos Islands and Australia, not merely

descend on native insects, reptiles and even birds,

but force people to change their behavior. The great

Aussie barefoot barbecue in the yard and children

playing shoeless or in sandals in the park may become

pleasures of the past if the fire ant, with its

excruciating bite, is not eradicated quickly.

 

And lest you think " it couldn't happen here, " one of

the fire ant species, the Argentine ant Linepithema

humile, has already made it to Japan. It was

discovered in 1993 in residential areas of Hatsukaichi

City, Hiroshima Prefecture. Be careful where you

tread.

 

The range of alien creepy-crawlies already found in

Japan is wide. No doubt because of the extent of trade

between the two countries, many of them originated in

the U.S. They threaten pine forests (the pine wood

nematode, Bursaphelenchus lignicolus, introduced as

early as 1905), cherry trees (the fall webworm,

Hyphantria cunea, a 1945 arrival, is a serious

defoliator of such trees) -- and even rice crops (the

rice water weevil, Lissorhoptrus oryzophilus,

introduced in 1976).

 

Lax controls at customs, airports and container ports

have allowed a wide range of aliens to enter Japan,

where the general level of public awareness about the

dangers of alien species is woefully low.

 

Not only might that accidental invertebrate devastate

a fruit crop, a tree harvest or out-compete a native

species, it might even threaten people. Mention

poisonous spiders, and many people will at least know

of the infamous American black widow with its

potentially lethal bite. A close relative of the widow

(although not as deadly) is the Australian red-back

spider, first reported here in November 1995 at

Takaishi, a port city in southern Osaka Prefecture.

 

Both infestations occurred at, or near, ports

receiving imports from Australia, where the red-back

is both common and widespread. When the related

Australian brown widow was found to have reached

Okinawa on Dec. 7, 1995, however, the discovery

complicated our understanding of the invasion routes

of these spiders. Okinawa is not a major port and

receives few Australian goods. The spider's means of

arrival remains a mystery.

 

Japan is by no means the first country to be colonized

by alien spiders. Red-backs have reached New Zealand

and, more amazingly, the remote South Atlantic island

of Tristan da Cunha. They are thought to have reached

the latter thanks to a satellite-station tracking unit

that was airlifted from western New South Wales to

Florida, where it was stored for three weeks before

being shipped to Tristan da Cunha.

 

But these examples are just the tip of the iceberg: No

fewer than 300 alien insect species have become

established in Japan since 1868. While not a new

phenomenon, alien insects are increasingly a force to

be reckoned with; they may bring pain, economic

hardship or carry diseases affecting crops -- or us.

That is no reason to wage war on all insects, but it

is certainly justification for stepping up control

measures at customs and immigration, and for

encouraging the teaching of insect taxonomy the better

to safeguard Japan's bio-integrity.

 

The Japan Times: Sept. 30, 2001

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