AboutZoos, Since 2008


Inva­sive alien species: a grow­ing prob­lem for envi­ron­ment and health

pub­lished 22 Feb­ru­ary 2013 | mod­i­fied 22 Feb­ru­ary 2013

American minkInva­sive alien species pose greater risks than pre­vi­ously thought for bio­di­ver­sity, human health and economies, accord­ing to two new reports from the Euro­pean Envi­ron­ment Agency (EEA).

An alien or non-​native species is an organ­ism which humans have intro­duced –inten­tion­ally or acci­den­tally –out­side its pre­vi­ous range. It is deemed ‘inva­sive’ if it has neg­a­tive effects on its sur­round­ings, for exam­ple by out­com­pet­ing or pre­dat­ing on native species that have evolved with­out spe­cific adap­ta­tions to cope with them. In such cases pop­u­la­tions of native species can be dev­as­tated. Evi­dence shows that in a grow­ing num­ber of cases inva­sive alien species even cause harm to human health and soci­ety.

In many areas, ecosys­tems are weak­ened by pol­lu­tion, cli­mate change and frag­men­ta­tion. Alien species inva­sions are a grow­ing pres­sure on the nat­ural world, which are extremely dif­fi­cult to reverse.
Jacque­line McGlade, EEA Exec­u­tive Direc­tor »

There are more than 10,000 alien species present in Europe, and the rate of new intro­duc­tions has accel­er­ated and is still increas­ing. At least 15 % of these alien species are known to have a neg­a­tive eco­log­i­cal or eco­nomic impact. How­ever, non-​native species — for exam­ple, some food crops — can also have huge ben­e­fits.

The first report, The impacts of inva­sive alien species in Europe, details the effects and spread of some species. The sec­ond report, Inva­sive alien species indi­ca­tors in Europe dis­cusses the method­olog­i­cal approach in bring­ing this data together.

The most com­mon rea­son species are intro­duced else­where is for hor­ti­cul­ture, while oth­ers may be brought into new areas for other rea­sons includ­ing farm­ing, hunt­ing, and fish­ing, or as pets, the report notes. Trans­port is not always inten­tional — for exam­ple, zebra mus­sels have stowed away in the bal­last water of ships to pro­lif­er­ate in Euro­pean lakes.

Increas­ing trade and tourism in recent decades may have led to increas­ing num­bers of alien species. Cli­mate change may also play a role in the spread of these species, the report says, mak­ing some areas more favourable to plants and ani­mals orig­i­nally from else­where.

Inva­sive alien species are one of the main threats to bio­di­ver­sity. Of the 395 Euro­pean native species listed as crit­i­cally endan­gered by the IUCN Red List of Threat­ened Species, 110 are in dan­ger because of inva­sive alien species. The EU Bio­di­ver­sity Strat­egy 2020 has pol­icy tar­gets which aim to address the problem.

Impacts on human health

For humans, one of the most dan­ger­ous effects of inva­sive alien species is as a car­rier of dis­ease. The Asian tiger mos­quito has been linked to more than 20 dis­eases, includ­ing yel­low fever and chikun­gunya fever. It has come to Europe mainly through the inter­con­ti­nen­tal trade in used tyres, and is now preva­lent in sev­eral south­ern Euro­pean coun­tries, espe­cially Italy. Cli­mate change pro­jec­tions show that the mos­quito will likely extend its range fur­ther north in com­ing years.

Cli­mate change is also enabling the spread north­ward of the com­mon rag­weed. The plant is orig­i­nally from North Amer­ica, the seeds first com­ing to Europe in mixes of grain intended as bird feed. It is a pow­er­ful trig­ger of hayfever and other aller­gies.

Chang­ing land­scapes are another result of inva­sive alien species. For exam­ple, the red palm wee­vil is destroy­ing large num­bers of palms in the Mediter­ranean region, trans­form­ing the green spaces in cities.

There are also effects on ecosys­tems which indi­rectly affect humans. In some cases ecosys­tems altered by inva­sive alien species may be less able to pro­vide impor­tant ‘ecosys­tem ser­vices’ which sup­port human activ­ity. For exam­ple, the pol­li­na­tion car­ried out by hon­ey­bees may be affected by inva­sive alien species — the yellow-​legged hor­net, native to Asia, has been found to dev­as­tate bee­hives in France.

Inva­sive alien species cost Europe around € 12 bil­lion per year, accord­ing to one esti­mate. Species such as the Span­ish slug, now found in most Euro­pean coun­tries, can dev­as­tate crops. Other species such as the per­va­sive zebra mus­sel can also cause high costs by foul­ing water fil­tra­tion plants and water cool­ing reser­voirs of power plants.

Inva­sive species harm­ing bio­di­ver­sity

Inva­sive alien species harm native species through pre­da­tion, as is the case of feral cats killing smaller crea­tures. Cats have been intro­duced to approx­i­mately 180 000 islands world­wide, and have a sig­nif­i­cant impact — in Britain alone, cats are esti­mated to kill 2529 mil­lion birds every year.

The Amer­i­can mink was orig­i­nally brought to Europe for fur farm­ing. Many ani­mals have since escaped or been inten­tion­ally ‘lib­er­ated’, so the species is now com­mon in the wild in many areas of Europe. It is now out­com­pet­ing its Euro­pean cousin in many areas, and has had dev­as­tat­ing effects on local wildlife, par­tic­u­larly ground-​nesting birds.

Amphib­ians around the world are in decline, in part due to the inva­sive chytrid fun­gus. Other alien species can spread dis­eases, as is the case with the red swamp cray­fish, which car­ries the ‘cray­fish plague’. The dis­ease often proves deadly to Euro­pean cray­fish, as they have not evolved to cope with the dis­ease.

Hybridi­s­a­tion can also be a prob­lem. For exam­ple, Japan­ese knotweed is a par­tic­u­larly vir­u­lent hybrid of two alien species orig­i­nat­ing from dif­fer­ent parts of Asia, which first came into con­tact as alien species in cen­tral Europe. The hybrid has been found to spread faster than its par­ents, out­com­pet­ing other plants and alter­ing ecosys­tems with effects on other species.

(Source: Euro­pean Envi­ron­ment Agency news release, 21.02.2013)

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