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Invasive Species May Not Be All Bad: Scientists

An active debate among biologists about the role of invasive species in a changing world is going on

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Invasive Species
The invasive European green crab is tearing down ecosystems in Newfoundland and building them up on Cape Cod. VOA
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Off the shores of Newfoundland, Canada, an ecosystem is unraveling at the hands (or pincers) of an invasive crab.

Some 1,500 kilometers (930 miles) to the south, the same invasive crab — the European green crab — is helping New England marshes rebuild.

Both cases are featured in a new study that shows how the impacts of these alien invaders are not always straightforward.

Around the world, invasive species are a major threat to many coastal ecosystems and the benefits they provide, from food to clean water. Attitudes among scientists are evolving, however, as more research demonstrates that they occasionally carry a hidden upside.

“It’s complicated,” said Christina Simkanin, a biologist at the Smithsonian Environmental Research Center, “which isn’t a super-satisfying answer if you want a direct, should we keep it or should we not? But it’s the reality.”

Simkanin co-authored a new study showing that on the whole, coastal ecosystems store more carbon when they are overrun by invasive species.

Good news, crab news

Take the contradictory case of the European green crab. These invaders were first spotted in Newfoundland in 2007. Since then, they have devastated eelgrass habitats, digging up native vegetation as they burrow for shelter or dig for prey. Eelgrass is down 50 percent in places the crabs have moved into. Some sites have suffered total collapse.

That’s been devastating for fish that spend their juvenile days among the seagrass. Where the invasive crabs have moved in, the total weight of fish is down tenfold.

The loss of eelgrass also means these underwater meadows soak up less planet-warming carbon dioxide from the atmosphere.

In Cape Cod, Massachusetts, the same crab is having the opposite impact.

Off the coast of New England, fishermen have caught too many striped bass and blue crabs. These species used to keep native crab populations in check. Without predators to hold them back, native crabs are devouring the marshes.

But the invasive European green crab pushes native crabs out of their burrows. Under pressure from the invader, native crabs are eating less marsh grass. Marshes are recovering, and their carbon storage capacity is growing with them.

Invasive species
In this May 8, 2016 photo, eelgrass grows in sediment at Lowell’s Cove in Harpswell, Maine. VOA

Carbon repositories

Simkanin and colleagues compiled these studies and more than 100 others to see whether the net impact on carbon storage has been positive or negative.

They found that the ones overtaken by invasive species held about 40 percent more carbon than intact habitats.

They were taken by surprise, she said, because “non-native species are thought of as being negative so often. And they do have detrimental impacts. But in this case, they seem to be storing carbon quicker.”

At the Smithsonian Environmental Research Center where she works, the invasive reed Phragmites has been steadily overtaking a marsh scientists are studying.

Phragmites grows much taller, denser and with deeper roots than the native marsh grass it overruns.

But those same traits that make it a powerful invader also mean it stores more carbon than native species.

“Phragmites has been referred to as a Jekyll and Hyde species,” she said.

Not all invaded ecosystems stored more carbon. Invaded seagrass habitats generally lost carbon, and mangroves were basically unchanged. But on balance, gains from marsh invaders outweighed the others.

Invasive species
Phragmites plants growing on Staten Island draft in a breeze in the Oakwood Beach neighborhood of Staten Island. VOA

Not a lot of generalities

To be clear, Simkanin said the study is not suggesting it’s always better to let the invaders take over; but, it reflects an active debate among biologists about the role of invasive species in a changing world.

“One of the difficult things in the field of invasion biology is, there aren’t a lot of generalities,” said Brown University conservation biologist Dov Sax, who was not involved with the research. “There’s a lot of nuance.”

The prevailing view among biologists is that non-native species should be presumed to be destructive unless proven otherwise.

When 19 biologists wrote an article in 2011 challenging that view, titled, “Don’t judge species on their origins,” it drew a forceful rebuke from 141 other experts.

Sax said the argument is likely to become more complicated in the future.

Also Read: Climate Change Not A Hoax: Trump

“In a changing world, with a rapidly changing climate, we do expect there to be lots of cases where natives will no longer be as successful in a region. And some of the non-natives might actually step in and play some of those ecosystem services roles that we might want,” he said.

“In that context, what do we do? I definitely don’t have all the answers.” (VOA)

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Old Dusty Kilogram Swapped for Something More Stable: Scientists

It has taken years of work to fine-tune the new definition to ensure the switchover will be smooth.

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Kilogram
The International Prototype of the Kilogram (IPK) is pictured in Paris, France, in this undated photo obtained from social media. VOA

After years of nursing a sometimes dusty cylinder of metal in a vault outside Paris as the global reference for modern mass, scientists are updating the definition of the kilogram.

Just as the redefinition of the second in 1967 helped to ease communication across the world via technologies like GPS and the internet, experts say the change in the kilogram will be better for technology, retail and health — though it probably won’t change the price of fish much.

The kilogram has been defined since 1889 by a shiny piece of platinum-iridium held in Paris. All modern mass measurements are traceable back to it — from micrograms of pharmaceutical medicines to kilos of apples and pears and tons of steel or cement.

kilogram, weight
Border Security Force officials showing 17 kilogram heroine.

The problem is, the “international prototype kilogram” doesn’t always weigh the same. Even inside its three glass bell jars, it gets dusty and dirty, and is affected by the atmosphere. Sometimes, it really needs a wash.

“We live in a modern world. There are pollutants in the atmosphere that can stick to the mass,” said Ian Robinson, a specialist in the engineering, materials and electrical science department at Britain’s National Physical Laboratory.

“So when you just get it out of the vault, it’s slightly dirty. But the whole process of cleaning or handling or using the mass can change its mass. So it’s not the best way, perhaps, of defining mass.”

What’s needed is something more constant.

kilogram, weight
The Kilogram. Flickr

So, at the end of a week-long meeting in the Palace of Versailles, Paris, the world’s leading measurement aficionados at the International Bureau of Weights and Measures will vote Friday to make an “electronic kilogram” the new baseline measure of mass.

Just as the meter — once the length of a bar of platinum-iridium, also kept in Paris — is now defined by the constant speed of light in a vacuum, so a kilogram will be defined by a tiny but immutable fundamental value called the “Planck constant.”

The new definition involves an apparatus called the Kibble balance, which makes use of the constant to measure the mass of an object using a precisely measured electromagnetic force.

Paris,diesel,kilogram, weight
The kilogram has been defined since 1889 by a shiny piece of platinum-iridium held in Paris.VOA

“In the present system, you have to relate small masses to large masses by subdivision. That’s very difficult — and the uncertainties build up very, very quickly,” Robinson said.

“One of the things this [new] technique allows us to do is to actually measure mass directly at whatever scale we like, and that’s a big step forward.”

Also Read: NASA to Send Organ-on-Chips to Test Human Tissue Health in Space

He said it had taken years of work to fine-tune the new definition to ensure the switchover will be smooth.

But while the extra accuracy will be a boon to scientists, Robinson said that, for the average consumer buying flour or bananas, “there will be absolutely no change whatsoever.” (VOA)