Friday, June 10, 2011

Invasive species

I cannot agree with the following entirely for in my state [Missouri] Zebra Mussels are a particular nuisance and problem. Yes, they are an exception but the embracement of invasive species must be done with caution and careful management.

"Ecologists: Time to End Invasive-Species Persecution"


Brandon Keim

June 8th, 2011


They’re treated as outsiders, as opportunity-stealing intruders who ought be greeted with government crackdowns rather than open arms.

They’re immigrants — immigrant species, that is. And some ecologists say it’s time to declare amnesty, demilitarize our environmental borders and accept the inevitable reality of non-native invasion.

“People like to have an enemy, and vilifying non-native species makes the world very simple,” said ecologist Mark Davis of Macalester University. “The public got sold this nativist paradigm: Native species are the good ones, and non-native species are bad. It’s a 20th century concept, like wilderness, that doesn’t make sense in the 21st century.”

Davis is one of 18 ecologists to sign a June 9 Nature essay entitled, “Don’t judge species on their origins.” They argue that while some non-natives are indeed destructive, such as Guam’s brown tree snakes and Great Lakes zebra mussels, they’re the exception.

Most are actually benign, relegated to a lower-class status that reflects prejudice rather than solid science, write the authors. Non-natives are assumed to be undesirable, and their benefits go ignored and unstudied.

As examples of unfairly maligned invaders, the authors mention Australia’s devil’s claw plants, subject to a 20-year-long plant hunt that’s done little to contain a species that may cause little ecological disturbance. In similar fashion, tamarisk trees in the U.S. southwest have been targeted for 70 years by massive eradication programs, but are now seen as providing important bird habitat. Ditto the honeysuckle, banned in many U.S. states, but providing an apparent boost to native bird biodiversity.

“Classifying biota according to their adherence to cultural standards of belonging, citizenship, fair play and morality does not advance our understanding of ecology,” wrote the essay’s authors. They also consider ecological nativism to be hypocritical — nobody’s complaining about lilacs or ring-necked pheasants — and a form of denialism: In a globalized, human-dominated world, plants and animals will get around.

“Most human and natural communities now consist both of long-term residents and of new arrivals,” they wrote. “We must embrace the fact of ‘novel ecosystems.’”

Many other ecologists, however, were dismayed by the essay. David Pimentel of Cornell University said many invasive benefits are indeed recognized: Ecologists hardly complain about corn and other non-native crop plants. He said Davis and colleagues cherry-picked their examples.

“This article … is biased and is not a fair representation of the risks and benefits,” said Pimentel, who has estimated invasive species damage in the U.S. at between $100 billion and $200 billion. His point was echoed by Jessica Gurevitch, an ecologist at the State University of New York Stony Brook. “I think they downplay some of the problems and uncertainties,” she said. “That we should just get used to it, is not correct.”

Davis said that non-native species need to be addressed on a case-by-case basis. “We’re not saying, ‘Everything is okay, let’s open the doors,’” he said. “What’s frustrated us is that the actual data has often been misrepresented. People have heard that non-native species represent the second-greatest extinction threat in the world, and it’s just not true.” Davis noted that in many places, non-native species actually increase total biodiversity.

But a different criticism came from David Lodge, a Notre Dame ecologist who studies Great Lakes Asian carp invasion. Those potentially fisheries-wrecking fish also embody what some biologists call ‘the homogecene’: Habitat disruption and non-native species flow reduce ecological uniqueness. Even as local biodiversity increases, each locale may come to resemble the next. “The researchers focus on biodiversity as the fundamental good. But what if that’s not the goal?” said Lodge.

There is, however, a common ground for these arguments: Each reflects the basic fact that, early in the 21st century, humanity is the driving force of nature on Earth. Whether species are classified as native or non-native, whether they’re accepted or rejected, reflects a choice. Philosophy guides stewardship, and stewardship is global.

“Humans are managers, humans are gardeners. We make the decisions about what species we want, and where,” said Lodge.

“To value the nature we actually have, and are creating, we need to think broadly,” said earth scientist Erle Ellis of the University of Maryland, Baltimore County, who invented the term ‘anthrome’ to define the hybrid human-natural systems that now dominate Earth’s surface. “Nature is something we create now.”

"Zebra Mussels: Missouri's Most Unwanted"


Conservation Commission of Missouri

Zebra mussels and a related species, quagga mussels, are fingernail-sized, black-and-white striped bivalve mollusks native to the Caspian Sea region of Asia.

They came to North American waters in international shipping ballast water and were discovered in Lake St. Clair near Detroit in 1988. Since then, zebra mussels have spread rapidly throughout the Great Lakes and connected waterways of the Mississippi River, including the Arkansas, Illinois, Ohio and Tennessee rivers.

Zebra mussels were first reported in Missouri in 1991 in the Mississippi River. For eight years, they were not found west of the Mississippi in our state. In spring 1999, however, zebra mussels were reported in the Missouri River near Sioux City, Iowa. In August 1999, zebra mussels were found in the lower Meramec River, a Mississippi River tributary south of St. Louis.

It's suspected that commercial barges originating from the Mississippi River, transported attached adult zebra mussels upstream to these previously un-infested areas. During the next several decades, zebra mussels could spread to other freshwater locations in Missouri and throughout North America.

Female zebra mussels can produce as many as 1 million eggs per year. These develop into microscopic free-swimming larvae (veligers) that quickly begin to form shells. At about three weeks, the sand-grain-sized larvae start to settle, and by suing they byssal threads, attach to any firm surface. They clump together and cover rock, metal, rubber, wood, docks, boat hulls, native mussels, crayfish and even aquatic plants.

Zebra mussels filter plankton from the surrounding water. Each mussel can filter about one quart of water per day. However, not all of what they remove is eaten.

What they don't eat is combined with mucus as "pseudo-feces" and discharged onto the lake bottom where it accumulates. This material, which may benefit bottom feeders, also may reduce the plankton food chain for upper water species. Diving ducks, the freshwater drum and other fish eat zebra mussels, but will not control them.

Zebra mussels can clog power plants, industrial and public drinking water intakes, foul boat hulls, decimate populations of native freshwater mussels, impact fisheries and disrupt aquatic ecosystems. Economic impacts of zebra mussels in North America during the next decade are expected to be in the billions of dollars.

Overland transport on boats, motors, trailers and aquatic plants poses one of the greatest risk for spreading zebra mussels. Larger adult zebra mussels can live several days out of water in moist, shaded areas.

Boats that have been moored or stored for more than just a day or two in zebra mussel-infested waters may carry "hitchhiking" mussels attached to their hulls, engine drive units and anchor chains. Boats that have been in infested waters for only a day or two are less likely to transport adult zebra mussels.

Microscopic zebra mussel velgers can survive in boat bilge water, livewells, bait buckets and engine cooling water systems, regardless of how long the boat has been in infested waters.

However, they will die very quickly when their hiding places are warmed in the sun or when they "blow dry" on the highway on the trip home.

[Only relevant material posted.]

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