Wednesday, January 03, 2018

Alien invasive species.

Glacier National Park. Baring Falls. Photo 8/15/12.
A pristine creek at the time of this writing.
Most people seem to know about invasive species and the damage that they can do to an ecosystem. Alien invasive species are organisms that are introduced into a foreign ecosystem, usually at a great distance from their native ecosystem, usually from another continent. That's the alien part. The invasive part is that they rapidly invade, populate, and exclude other species in the new territory. Some may refer to them as exotic species. Some may refer to them as noxious weeds, but some noxious weeds are native plants that have been branded as undesirable because of economics, cultural norms, or ignorance. 
Why the fuss? - after all, they are just plants.
It is like this: A kid on holiday goes overseas and picks up a microbe. Easy enough to do. But he has no immunity to this one; his immune system has never seen it before. He returns home and goes back to school. He starts to cough. Next, all the kids start to cough. Then the teachers start to cough. The principal gets a cough. Nobody has immunity to the microbe and it runs amok. So the school sends everybody home and locks the doors. Quarantine. Police tape. Face masks. At home, their bodies work long and hard to develop an adequate immune response. But some immune systems are not strong, fast, or educated enough. The microbe wins. The body loses. Enough losses and the school is shut down for good.
It's this way with AIS. Introduce a foreign organism into an ecosystem and there may be no defense against it, in this case, no predators, parasites, weather patterns that would check its advance, weaken or kill it. So it runs amok. If it continues to dominate and exclude the native species, the original ecosystem may be damaged, no longer be recognizable, or it may be gone for good.
A prime example of this is salt cedar, or tamarisk (Tamarix sp.), brought to North America from the Middle East in the 1800's, which has invaded riparian areas in the American southwest, making the native southwestern riparian area one of the rarest ecosystems in the US. Guns, bombs, napalm won't stop it. It's a phreatophyte, driving roots to extreme depths to take up water, so much so, that they are consuming 2-4.5 million acre-feet of water per year, enough for 20 million people for one year. Other threatened ecosystems are northeastern forests (garlic mustard), southern waterways (water hyacinth, nutria), Great Lakes (gobi, zebra mussel, Asian carp), southeastern forests (Kudzu), Yellowstone Lake (lake trout), glaciated northern forests (alien invasive earthworms (yes)). It's a long list.
But AIS isn't always plants, mammals, birds, fish, reptiles, and insects; lately, we have come to know it can involve tiny species invisible to the naked eye. That kid who suffered wasn't eaten by an escaped lion. So too, ecosystems can be brought to the brink by alien, invasive microbes. You may be familiar with some of these in North America: Dutch Elm Disease (American elm), Whirling Disease (trout and salmon), White-nose Syndrome (bats), and Viral Hemorrhagic Septicemia (fish). And then there is Didymosphenia geminata, known as Didymo, an AIS diatomic algae expanding and bullying its way into clear streams around the world - North America, Australia, Argentina, Chile, New Zealand. Apparently, it was introduced on the soles of waders worn by globe-trotting trout fishermen. Even in its native habitat, North America and Europe, it has exploded and expanded its range. Some research indicates that this is a result of climate change.
Still, some folks think that all the fuss about AIS is unfounded, reasoning that nature has been moving species around for eons and that everything is a non-native species at one time or another, there is no need to worry, the earth accommodates them all. True, but we are moving hundreds of millions of airline passengers at hundreds of miles per hour and hundreds of millions of those metal shipping containers across the oceans every year. Is that the background species migration rate? And we have to ask, if this is no big deal, do these folks get vaccinated before they travel overseas?

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