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October 18, 2005

Sudden Oak Death & The Invasion of the Mud Snails

It seems like every time I go to a state or national park lately, I encounter some sort of warning about some invasive species threatening the area - directly or as vectors. Sometimes it's a disease that kills off ancient trees, other times its an aggressively growing garden plant that's choking up waterways, and still other times, it's a non-native animal with no natural predators multiplying like crazy - like the Burmese Pythons in Florida we talked about last week.

Sudden Death

Last time I went for a hike at Elkhorn Slough along the Monterey Bay, I had to step through a shoe chemical treatment to help prevent the spread of Sudden Oak Death. There was also a "least wanted" list posted which identifies Monterey Bay's worst invasive species.

According to the latest California Oak Mortality Task Force Report, the approximately 50,000 visitors annually are asked repeatedly to clean their shoes before walking on the trails of the slough in order to to prevent the introduction and spread of Sudden Oak Death - a devastating mould infection.

Invasion of the Mud Snails

When we arrived at our campground in the High Sierra this past weekend, we were ready for bear warnings, some moderately severe end-of-autumn storms and some kamikaze fishermen. What we got was a warning to help stop the spread of one of the many invasive species threatening the Sierras - the New Zealand Mud Snail - an invasive little mollusk that hides out in fishing gear.

The New Zealand Mud Snail is one of the leading invasive species threatening some of the endangered native fish all along the Pacific Northwest rivers. Unfortunately, the snail can reproduce asexually and shows a resistance to the common treatments used to combat other pests. However, once established, the little snails disrupt the food chain by eating the algae. Soon all the little insect larva that eats the algae is starving, and guess what eats the larva - baby salmon and baby trout. One of the primary ways in which these little mud snails spread is by hiding out in fishing gear like waders.

There was also a sign to help prevent the spread of the Asian Longhorned Beetle as well. It's become well-established on the East Coast and has caused a lot of damage. At first, they've only shown up in Chicago and New York, where they've decimated maple, horsechestnut, elm, willow, birch, poplar, and ash trees. Then they spread to nearby New Jersey. Now they've come to California...

Invasive Species Force Native Species Out

Non-native species enter the environment in all sorts of ways:

By hiding out in the ballast water of shipping vessels
By releasing an exotic snake into a nearby swamp
By dumping a water garden into a stream
By visiting a foreign environment and then visiting a local one

The one thing that's common about invasive species is that once they've become established, they influence the food chain and how all plants and animals work together in an environment. Non-native species often have few or no predators, allowing them to thrive while stealing the very resources needed by native species.

All native species are at risk when invasive species are introduced, whether by accident or on purpose in some cases. But it's the species that are already endangered that are of the greatest concern.

Almost half of the species on the U.S. endangered species list are threatened wholly or partly by introduced species.

More At: Huge, Freed Pet Pythons Invade Florida Everglades

That said, it should also be noted that invasive species has a greater potential of rendering a healthy population of a native species endangered, as well.

Combating The Invasion

In 2004, the Forest Service Chief Dale Bosworth gave a speech highlighting the Four Threats to the Nation's Forests and Grasslands - fires, invasive species, development, and unmanaged outdoor recreation. The Four Threats Projects were launched to help focus Forest Service policies to address the concerns, and all of these warning signs and public education programs are part of this fight against invasive species.

The U.S. spends $13 billion per year to prevent and contain the spread of invasives. For all invasives combined, the price tag is $138 billion per year in total economic damages and associated control costs.

More at: US Forest Service: Four Threats

Despite being a huge money sink, from a legislative perspective, the future isn't bright. Various bills in Congress, aimed at combating invasive species, are languishing. The Endangered Species Act itself is under threat, including some proposed invasive species changes that could cripple the act.

Legislation aimed at preventing foreign fish, clams and marine creatures from entering ... in oceangoing ships is languishing in Congress while the shipping industry pushes a less restrictive bill.

More at: Bill aimed at invasive species languishes

More About Invasive Species

If you're interesting in more about how invasive species are affecting our environment, you may want to check out some of the following resources. Dr. Jennifer Forman Orth runs an Invasive Species weblog worth checking out and there's also InvasiveSpecies.Org, a joint organization including the US Forest Service. Lastly, the National Wildlife Federation has a couple good examples of invasive species and their biological and fiscal impacts.

I also have written about specific invasive species here before, for example:

Gator Gluttony: A Python's Fatal Mistake
Endangered Species Act Could Become Extinct

Posted by sorsha at October 18, 2005 7:44 PM