Invasive Species are more Beneficial than Alarmists will Admit

Every organism that ever evolved became an invasive species.  It colonized new territory where it previously had not existed.  The concept of an invasive species that is harmful to the environment is a construct invented by man, the most environmentally damaging species to ever evolve.  The Homo sapien is such an hypocritical species.  The biogeographical history of the earth is a tale of species invading new territories.  The Bering Landbridge allowed a back and forth migration between Eurasia and North America, and the emergence of Central America offered a highway for another interchange of flora and fauna.  Man, the ultimate invader, has facilitated and accelerated the transfer of many species. Environmentalists focus on the harmful results invasive species wreak on ecology but ignore the obvious benefits that may in most cases outweigh the damage.  I mentioned 1 example on my blog last week–Burmese pythons reduce the population of predators that prey on endangered sea turtle eggs.  A recent study (referenced below) gives many more examples of beneficial invasive species that according to the authors of that study should be referred to as “recently arrived species.”

–The honeybee is not native to North America, yet without this “recently arrived species” industrial scale fruit and nut orchards would not be economically viable.

–Environmentalists mistakenly thought non native tamarisk trees were causing low water levels on the Colorado River floodplains.  Millions of dollars were spent eradicating this species.  But later studies showed tamarisk trees were not responsible for causing these low water levels.  Their misguided policy greatly reduced nesting habitat for the endangered willow flycatcher, a species that uses tamarisk in lieu of willow.

Endangered southwestern willow flycatcher’s nest in a non-native tamarisk tree.  The government and groups like the Nature Conservancy spent millions eradicating this species of tree based on the false premise that it lowers water levels.  Now this rare bird has far less nesting habitat.

–Native trees can’t be re-established on eroded Puerto Rican forestlands unless non-native trees are planted first.  With the help of non-native trees, 20 species of native trees were able to grow on badly eroded soils.

–The presence of non native honeysuckle vines increases the population of robins and catbirds that feed on the berries.  The increased bird populations acted as dispersers that helped increase native honeysuckle vine abundance.

–Non native guavas in Kenya helped increase the population of fruit-eating birds there.

–Non native grasses planted on reclaimed strip mines increased the population of endangered Henslow’s sparrows.

–Non native shad serve as forage to help feed  Pacific salmon.

–Non native mussels serve as food for raccoons.

–Butterflies utilize non native species as sources of food.

–Non native cattle maintain early successional habitat, thus helping native species dependent upon this habitat.  They’re a substitute for extinct Pleistocene megafauna.

–African honeybees traverse the areas between fragmented forests in Brazil, aiding the pollination of plant species that could become inbred and sterile.

Some regions provide refuge for species that are endangered in their land of origin.  The Aldabra tortoise is native to a Seychelles Island but is more common in Mauritia where it occupies the ecological role of a now extinct species of giant tortoise.

Aldabra Giant Tortoise Geochelone gigantea edit1.jpg

The Aldabra giant tortoise has been introduced to the island of Mauritia where another species of giant tortoise was overhunted into extinction centuries ago.  It serves as an important disperser of native plants.

Banteng, an endangered species of cattle native to southern Asia, breeds successfully in northern Australia.

Banteng bull caught on camera trap in Malua BioBank. Photo by: Sabah Wildlife Department (SWD).

Banteng cattle face extinction in their homeland but have successfully established a wild breeding population in northern Australia.

Hippos (imported by a rich cocaine baron) thrive in Colombia.  Game ranches in Texas are the best hope for breeding black rhinos, currently extinct in Africa.

Recently arrived species can cause the extinction of competing native species, but they can also instigate the evolution of new species.  Non native house sparrows appear to be speciating in North America, according to the geographic region they have colonized.  Desert populations of house sparrows have distinct physical characteristics from those found in eastern woodlands.  A new species of honeysuckle fly exists today, thanks to non native honeysuckle vines.  This species resulted from the hybridization of 2 closely related flies that hosted 2 different species of native honeysuckles.  The 2 different species of fly both hosted non native honeysuckles, explaining how they began breeding with each other.

The lonicera fly is the result of hybridization between 2 different species: Rhagoletes menax X R. zephyra.  This new species resulted from the introduction of non native honeysuckles.

The authors of the below referenced study suggest recently arrived species should be more carefully evaluated and managed and not blindly eradicated, simply because they are non native.

Reference:

Schlaepfer, Martin; Dow Sax and Julian Olde

“The Potential Conservation Value of Non-Native Species”

Conservation Biology 25 (3) June 2011

 

 

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