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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

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)

Next Story

Scientists Reform Face Of Another Human Ancestor

Now, Scientists have come up with a reformed face of a human ancestor

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human, ancestor, scientists, sculpture
This image shows a preliminary portrait of a juvenile female Denisovan based on a skeletal profile reconstructed from ancient DNA methylation maps. IANS

Exactly what our Denisovan relatives who lived 100,000 years ago might have looked like had been anyone’s guess for a simple reason – the entire collection of Denisovan remains includes a pinky bone, three teeth, and a lower jaw. Now, Scientists have come up with a reformed face of a human ancestor.

Now they have got a face. Using genetic data, scientists have now produced reconstructions of these long-lost relatives.

“We provide the first reconstruction of the skeletal anatomy of Denisovans,” said study author Liran Carmel of the Hebrew University of Jerusalem in Israel.

“In many ways, Denisovans resembled Neanderthals, but in some traits, they resembled us, and in others they were unique,” Carmel said.

Overall, the researchers identified 56 anatomical features in which Denisovans differed from modern humans and/or Neanderthals, 34 of them in the skull, according to a report published in the journal Cell.

For example, the Denisovan’s skull was probably wider than that of modern humans or Neanderthals. They likely also had a longer dental arch.

Rather than relying on DNA sequences, the researchers extracted anatomical information from gene activity patterns.

human, ancestor, scientists, sculpture
Using genetic data, scientists have now produced reconstructions of these long-lost relatives.
IANS

Those gene activity patterns were inferred based on genome-wide DNA methylation or epigenetic patterns.

To test the method the researchers developed, they first applied it to two species whose anatomy is known: the Neanderthal and the chimpanzee.

They found that roughly 85 per cent of the trait reconstructions were accurate in predicting which traits diverged and in which direction they diverged.

By focusing on consensus predictions and the direction of the change, rather than trying to predict precise measurements, they were able to produce the first reconstructed anatomical profile of the little-understood Denisovan.

ALSO READ: Here’s How A Wearable Device Can Regrow Hair On Bald Head

The evidence suggests that Denisovans likely shared Neanderthal traits such as an elongated face and a wide pelvis.

It also highlighted Denisovan-specific differences, such as an increased dental arch and lateral cranial expansion, the researchers said.

“Studying Denisovan anatomy can teach us about human adaptation, evolutionary constraints, development, gene-environment interactions, and disease dynamics,” Carmel said. (IANS)