Unintended Consequences Removing a Foreign Species

[Teamcasa]

I was reading this thread and it talked about a non-native lionfish being introduced into Florida’s costal waters. The question came up about removing them and what effect the species may have if left un-checked. Here in SoCal, we have a growing problem with an invasive seaweed. I’m sure there are thousands of other examples of non-native species being introduced to our seas and I don’t want to turn this into an argument revolving around any one specific foreign introduction but I would like discussion about how to treat it.

My initial reaction is that in most cases it’s too late to do anything other than prevent additional introductions. I feel that once a species has established itself, removing it may do more unintentional harm than good.

Dave

 

[MeiLing]

I don't think that it's true that removing any non-native species does more harm than good. Any time a non-native species gets labeled invasive, it's because there is nothing to keep that species in check and it is quite likely decimating a native species and upsetting an eco-system.

While all eco-systems have their own nuances, some are particularly vulnerable such as those in the Pacific Islands. As an example, look at what the introduction of the brown tree snake has done in Guam. Guam no longer has a bird population because this non-native species was introduced and it killed all the birds. Because of that, Hawaii is ever-diligent that it doesn't happen here. We have other non-native problems though that are also problematic such as coqui frogs from Puerto Rico.

If non-native species that is introduced has a native species that can keep the new species in balance, then there usually isn't a problem. Then there's a check to keep the balance. It's a gamble though as the full impact of an introduction is not calculated.

It is frequently the case here where eridication of non-native species of plants is constantly being undertaken to allow the native species to maintain their delicate foothold. Non-native animals are culled as well such as feral pigs and axis deer. And they are always on the lookout for other non-native animals, especially those that might have the capabality to hermaphroditically reproduce such as snakes and other reptiles.

 

[archman]

My initial reaction is that in most cases it’s too late to do anything other than prevent additional introductions. I feel that once a species has established itself, removing it may do more unintentional harm than good.

Dave

You are correct. It is generally held that once an invasive species establishes a foothold, it's there to stay. Removal by chemical or mechanical means may be prohibitively expensive or simply impossible. In many cases the invasive has altered the local ecology to such an extent that its removal would be immediately detrimental.

Examples of such invasives tend to be plants (eg. elephant ear, hydrilla, salt cedar). Their removal does nasty stuff like facilitate erosion and destroy habitat.

Wildlife managers take extraordinary steps in evaluating invasive species removal. The process is long and exhaustive; consensus for removal is often considered not practical (outside of designated refugia). That's why catching invasive species while they're still in the "exotic" phase is so terribly important. At that point, managers still have a reasonable chance of eradication.

Many people confuse the terms "invasive species" with "exotic species". While both usually refer to a non-indigenous, the former typically grows like a weed and detrimentally affects a given ecology.

 

[RoyN]

I wouldn't do it anyway because its like a giant human picking your house while you're still in it and putting it on Mars.

 

[drbill]

When I was Vice President of the Conservancy which owns 88% of Catalina Island, we had to identify and prioritize the hundreds of non-native plants that have invaded Catalina over the past three centuries. We spent many months identifying which ones were doing the greatest ecological damage, which ones had the highest probably of successful control or removal, etc. As Archman says, it is a difficult and detailed process.

Most of our successes were with non-native plants that had recently invaded the island and were still limited in their distribution. Of course with terrestrial plants, one has to recognize that removal of the mature plants does nothing to the soil seed bank which may have seeds of that plant in it for decades or longer. Monitoring and control efforts have to be on-going.

When we removed the thousands of feral European goats on the island (successfully I might add), we had to assess the consequences of removing this species which had been on the island since at least 1828 (first written records). We knew that removing them would (1) increase the threat and spread of non-native plants, (2) increase the overall fuel loading of the island leading to a potentially higher fire frequency and intensity, (3) potentially expand the mule deer population due to the removal of competitive pressure from the goats, thus increasing the food resources, etc.

Looking at our most recent marine introductions, Sargassum filicinum invaded the island in April of 2006. During that year it rapidly spread all along the leeward coast of Catalina (I have yet to see it on the windward side, but dive there far less frequently). We had considered removing/controlling it in the dive park, but there were a number of factors which limited our ability to do so.

The extremely warm waters of last summer caused a massive die off of even the deeper water giant kelp (Macrocystis), thus increasing sunlight levels on the bottom and allowing S. filicinum to explode. This year surface temps are about 5-6 degrees lower and the giant kelp is surviving at least below the surface. I'm starting to see sprouts of what must be young Sargassum plants so we'll see how they fare this year. As with land plants, there are spores of that species on the rocky bottom just waiting for the right conditions to explode.

A previous invader, Sargassum muticum, seems to have established some balance with the Macrocystis and although it does pop up in the late summer, it doesn't dominate as we once feared when it first arrived. We'll see what happens in the future.

Dave, I don't see how the removal of an invasive species can be negative except in the short-term due to disturbance. If we had effective ways to remove these invasives, I'd be all in favor of doing so. I have seen few of our native species that depend on the S. filicinum, although I have seen giant kelpfish hide and possibly nest in it, and several species of fish feed on attached algae and invertebrates. However, this would happen with the native species that would replace them once the competition for substrate and light was eliminated.

 

[Teamcasa]

Dr. Bill, There are many cases were the cure for an invasive species was worse than the damage/change of environment caused by an invasive species. Fire control in Yellowstone/Yosemite, The whole Salton Sea issue, and Eucalyptus trees in California (and elsewhere). While I’ll agree that sometimes it is warranted to remove or eradicate an invasive species, we need to clearly study and examine all of its ramifications beforehand. Clearly discovering the invasion early gives us the best chance of solving the problem.


This states one side of the argument: From this site
“A group of contrarian ecologists has recently minimized the overall importance of introduced species as a threat to biodiversity and intact ecosystems. Some have echoed a charge by a few sociologists, anthropologists, and philosophers that concern with biological invasions is little more than displaced xenophobia and nativism. They are wrong on both accounts: biological invasions are a huge threat to many intact ecosystems and ultimately to global biodiversity, and there is no evidence that modern invasion biology is motivated by anything other than normal concerns for conservation. Most of the focus on impacts of introduced species has been on population impacts of one species on another – predation or herbivory by invaders on poorly defended natives, introduced pathogens ravaging susceptible native hosts, and the like. In fact, many introduced species wreak havoc on entire ecosystems, and not only by modification of nutrient cycles. Often invaders change the physical structure of an area to the disadvantage of many resident species. Others modify fire regimes. The phenomenon of invasional meltdown, whereby two or more introduced species facilitate one another’s establishment and exacerbate the effect on native species and systems, is poorly studied, but a growing number of examples point to its importance in enhancing invasion impacts.”

Dave

 

[Hank49]

I think the situation is pretty hopeless regarding uncontrolled transfer of marine organisms worldwide. How can you disinfect ships pulling into any international port coming from who knows where? I've seen studies in San Francisco Bay where almost all the seaweeds and organisms a biologist was pulling off some rocks there were exotic, or invasive, from all over the world.
Panamanian stocks of penaeus Vanammei are resistant to more viruses than almost any other cultured shrimp population in the world. The theory is that they've been exposed to many foreign viruses brought in by ships entering the canal, and have become resistant over the years.
I think we have a much better chance at controlling terrestrial organisms, but we're fighting an uphill battle there too.
Hey Archman....I didn't say it. Hah!

 

[archman]

Hey Archman....I didn't say it. Hah!

Wussie. I'll say it.

"KILL THE LIONFISH":bigun2:

 

[Hank49]

I don't think that it's true that removing any non-native species does more harm than good. Any time a non-native species gets labeled invasive, it's because there is nothing to keep that species in check and it is quite likely decimating a native species and upsetting an eco-system.

If non-native species that is introduced has a native species that can keep the new species in balance, then there usually isn't a problem. Then there's a check to keep the balance. It's a gamble though as the full impact of an introduction is not calculated.

It is frequently the case here where eridication of non-native species of plants is constantly being undertaken to allow the native species to maintain their delicate foothold.

Has a non native species ever been successfully removed anywhere? It seems we've had more "success" at removing (extinction) native species.
I remember trying to remove Sleepy Grass from a small farm in Hakipu'u back in the 70s. We diligently pulled it out by the roots and burned it. By the time we'd crossed from one side to the other, it had small plants coming back where we'd started. It's really hard to eradicate a living organism.....unless you DON'T want to. Hawaii is especially susceptible to invasives being so young, if you believe in Darwinism. California grass, philodendron, mina birds, Brazilian cardinals, red cardinals, sparrows, cattle egrets, tilapia, ta'ape, mongoose, bufo marina, american bullfrog, pheasant (on Kauai where there's no mongoose) ...the list goes on of invasive organisms that now dominate there.
KILL THE LIONFISH !!

 

[MeiLing]

I don't think they've ever been entirely successful at removing non-natives, but they certainly try to keep them in check so as to leave room for the natives. The biggest ones in the news now are the coqui frogs (tiny Puerto Rican tree frogs that have come in bromeliads). They croak all night at a sound level that is deafening. They have no predators and they're pretty resistant to all that they tried to get rid of them. Like one of the previous posters said, it's a delicate balance of trying to get rid of the non-natives while not killing off the natives. So many of our native birds are on the verge of extinction.