October 10, 2012
Invasive Species In The River Thames Are Major Drivers Of Biodiversity Loss
Alan McStravick for redOrbit.com - Your Universe Online
A new study out of the U.K. points out what many ecosystems of the world have already known. In this new study, scientists from the Queen Mary, University of London, claim that almost 100 non-native freshwater species have successfully invaded the River Thames, making it one of the world´s most highly invaded freshwater systems.
Published in the journal Biological Invasions over the weekend, scientists suggest that previous introduction of legislation intended to prevent the introduction of non-native species across the U.K. has been largely unsuccessful. They contend that the effect on the British economy due to these non-native invaders totals £1.7bn every year, or approximately $2.7bn/year.
Pointed out by lead author of the study, Dr. Michelle Jackson, who conducted this research as part of her PhD at Queen Mary, “We have identified 96 freshwater non-native species in the River Thames catchment and modern invasion rates (post 1961) reveal that one non-indigenous species is discovered every 50 weeks."
“Our research suggests that globalization [sic] has facilitated species invasions because of shipping activity and population size in the catchment had a positive correlation with the discovery of non-native species.”
The United States is no stranger to non-native invaders, either. The National Parks Services has a few interesting examples on their website.
The Florida Everglades and its native communities have been under attack from invasive exotic species. From exotic fish devouring native species to the Melaleuca tree that shades out indigenous plants, the Florida Everglades is experiencing a wide barrage of pressures from the introduction of non-native species.
One of the reasons that these introduced species have a competitive advantage over native species is that, being they are so far removed from their native habitats, there simply are no natural predators around. This allows them to multiply virtually unchecked, taking valuable resources (sunlight, water, nutrients) from the native species. A full 68% of extinctions in the U.S. can be attributed to the introduction of invasive exotic species, making this method of extinction and endangerment second only to complete habitat destruction.
The National Parks Services also points out, like the British study, there is a financial impact of exotics, citing researchers from Cornell University, who say the economic damage is $120 billion per year. That figure exceeds the budgetary allotments for the Departments of State, Commerce and Homeland Security combined.
Another national park affected by invasive species is located in the state of Texas. Big Bend National Park. Big Bend is not as friendly an environment as the Florida Everglades, but that fact doesn´t exclude Big Bend from the hazards associated with invasive species.
On the site, they lament the introduction of the Salt Cedar, also known as the Tamarisk. The history of the Tamarisk in the desert southwest dates back to the early 1900´s, when they were introduced as windbreaks and to lessen the impacts of soil erosion. With study and the benefit of hindsight, the irony of this is apparent as the Tamarisk is responsible for some of the most erosive features on the Rio Grande.
Adding to that is the tree´s rate of spread and its resistance to cold temperatures, fire, floods and drought. Also, the Tamarisk is responsible for a high rate of evaporation of significant amounts of water.
Another insidious invader affects private, commercial and governmental operations. Kudzu, first introduced in 1876 at the Philadelphia Centennial Exposition, was lauded as a fantastic combatant of erosion and farmers were encouraged to plant kudzu from the mid-1930´s thru into the 1950´s. It was in 1953 that kudzu was removed from the U.S. Department of Agriculture´s list of permissible cover plants as its categorization was changed to recognize it as a pest species. Unfortunately, the damage had been done. With just 20 years of wide agricultural use almost 80 years ago, the dominant kudzu now covers an estimated 7 million acres of land in the U.S. deep south.
With the kudzu´s ability to grow roughly one foot per day, it can grow over anything in its path, including other plants, buildings and road signs. The kudzu will kill other plants by depriving them of necessary sunlight. Also, stems and tree trunks will be girdled by the kudzu, breaking branches and even uprooting trees and shrubs.
The Queen Mary, University of London researchers, for their study, performed an exhaustive analysis of pre-existing databases, field surveys, literature and atlases to establish a list of invasive species in the Thames.
According to Dr. Jackson, “Invasive species are major drivers of biodiversity and ecosystem service loss, and multiple invaders have the potential to amplify one another´s impact."
“Our research highlights the need to establish how these multiple invaders interact.”