Posted by: maximos62 | July 29, 2009

Sudden Oak Death

Globalisation, specifically the expansion of global trade over the past 150 years has had a significant impact on the biosphere.  Organisms that were once confined to particular ecological niches have been intentionally and unintentionally transported far and wide.  Where both macro and micro floral once lived in relative equilibrium in their natural ecosystems, this is no longer the case.  Australian Melaleuca have become a pest in the Florida Everglades.  Originating in the Americas, plants such as Lantana, Lantana camara, and Madeira Vine, Anredera cordifolia, have become serious invasive weeds, both damage natural environments with the former emerging as a challenging weed infestation in pastures, and farmland throughout the tropics and sub-tropics.

Similar issues have arisen in the riparian and marine environments. Water hyacinth, Eichhornia crassipes, native to the upper Amazon system, has become one of the world’s worst aquatic weeds.  Global shipping has also a significant impact on marine ecosystems. Ships take on stabilising ballast water in one port with its particular ecosystem and later discharge that water in another port.  There is a risk that organisms transported in the ballast water can colonize new ecosystems affecting the balance and biodiversity of the recipient ecosystem.

The global trade in nursery plants has proven an efficient conduit for the globalisation of certain organisms. “Plant pathogens can equally overwhelm an entire ecosystem. The chestnut blight fungus arrived in New York City in the late 19th century on nursery stock from Asia and in less than fifty years had spread over 225 million acres of the eastern U.S., destroying virtually every chestnut tree.” From Impacts of Introduced Species in the United States, by Daniel Simberloff.

More recently a pathogen known as Phytophthora ramorum has been introduced to west coast Oak forests.  The pathogen was also discovered in European nurseries in the mid 1990s, now it has spread to Oak forest land in the U.K. and the Netherlands.  I’ll wrtite a lot moere about this.  It was something I was observing on my recent trip to Scotland.  In the meantime this video clip offers a good coverage on the problem in the USA.

I’m preparing an article on the impacts of the global rhododendron trade on Scottish Oak forests.  In the United Kingdom the impact of  P. ramorum has been compounded by the recently discovered P. kernoviae which also attacks Oak trees and is also hosted by rhododendron, mainly rhododendron ponticum. Any comments, photos to supplement my collection, insights, anecdotes or links or observations  are most welcome as I’m sure they could be of great help on this topic. I’ve already bookmarked quite a lot of material as maximos_russell on Delicious.


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