Prickly pear, an introduced type of cactus, ran amok in Australia till the Cactoblastis moth - which feeds on prickly pear - was introduced.
I’ve never heard of anything but positive consequences of the latter introduction. However this example is a bit of a cheat since it was an introduction of a non-native species to fight an introduction of a non-native species.
Dung beetles mentioned above are an example of the same thing.
The question is a little confusing; the title refers to Invasive species, but the question actually asks about positive effects from simply new species introductions. By definition part of what an “invasive” species does is cause harm, so you can’t really have any examples of harm-causing species causing no harm.
Also the questions asks about “mostly” positive results, but what’s the definition of that? Introducing tropical fish to a hot springs area in Banff certainly wiped out or radically changed whatever had been growing in the warm water for thousands of years prior… but we don’t really know what that was and it’s gone now. We’re left with this unique “wild” population of tropical fish growing in an alpine northern mountain region confined by temperature, and providing a tourist attraction and learning opportunity. Not sure if that would count.
Or, the introduction of sterile fish to empty ponds (for example large excavations that didn’t exist before the quarry was dug) for fishing might be examples. The fish can’t escape or breed, they didn’t displace anything, they provide some food for wildlife, and we get to catch them.
Sorry for the poor wording. By “new” I meant introduced to a new ecosystem.
I used “mostly” because nothing will be 100% positive. I was looking for something where the positive out weighs the negative.
True but bison will argue about anything.
Especially ones from upstate New York, I’ve heard.
They are a big problem in the South of Europe: they use up an enormous amount of water and burn like gasoline. They were introduced for the paper industry, many people who live were they are grown do not even know they are a foreign species! Crazy. They have no predators at all here, not even koalas. Insects die when they try to eat them.
I once started a book about a doctor in the middle ages. When he started making an Eucalyptus potion around page 15 I threw the book as far as it would fly. By showing how clever the doctor was the author showed how stupid what an ignorant he was.
This!
Oh boy. You’re entering a minefield worse than walking through a field of horse patties.
They’re incredibly contentious. Are they wild or feral? One one side you get “horse people” who want to preserve them completely and on the other side ranchers etc who want to nuke them all from orbit. You decide who to trust, but most wildlife biologists would say that being invasive is not an invitation for removal but the estimated population size that allows for sustainable use of the environment has been exceeded many many times over. They’re everywhere here in Nevada, and seem to have a detrimental effect on native wildlife. Not as bad on the environment as pigs, but they compete with deer and antelope range, and potentially increase the predatory load. One one hand we already tolerate and even encourage invasive species (pheasants are from Asia), and they provide some tourism draw. But on the other hand they can’t be managed like native or other invasive animals by the state wildlife agencies or federal land agencies, they’re protected by a law and any attempt would get you mired in lawsuits by people with little skin in the game but who feel affinity for horses. The protections in some cases exceed those granted to actual endangered animals, and there’s no shortage of them. What treatments they can do is things like expensive temporary sterilizations of dubious efficacy. You can also buy one as a pet or farm animal for very cheap, but they need to be broken and most people can’t do that.
Needless to say, whatever the solutions are the current situation is not sustainable. It causes lots of friction, but no solution is in sight.
As I mentioned above, horses are native American wildlife. A few thousand years absence is a drop in the bucket.
The cat’s out of that bag, so again, completely removing them is probably not happening. But the environment has drastically changed since then, and the management used for actually native species is not usable on Equus sp.
So let’s import koalas to California and southern Europe to eat the eucalyptus trees.
Why are they named eucalyptus? Maybe they should be named dyscalyptus.
Koalas are a fragile species that are having trouble surviving even in Australia, and make no appreciable dent on eucalyptus numbers even here.
The solution to invasive species is . . .
. . . more invasive species!
/s
Maybe if they didn’t riddle themselves with STDs, they’d be more robust…
We’ve tried to teach them to use condoms but frankly they aren’t inordinately bright and the concept seems to elude them.
Sometimes, yes. Purple Loosetrife was (is) a major problem. Some introduced species have brought it under control. About two decades ago I can remember seeing vast fields of it around here. From Wikipedia:
Purple loosestrife provides a model of successful biological pest control. Research began in 1985 and today the plant is managed well with a number of insects that feed on it. Five species of beetle use purple loosestrife as their natural food source, and they can do significant damage to the plant. The beetles used as biological control agents include two species of leaf beetle: Galerucella calmariensis and Galerucella pusilla ; and three species of weevil: Hylobius transversovittatus , Nanophyes breves , and Nanophyes marmoratus . Infestations of either of the Galerucella species is extremely effective in wiping out a stand of purple loosestrife, defoliating up to 100% of the plants in an area. The moth Ectropis crepuscularia is polyphagous and a pest species itself, and unsuitable for biological control.[20]
Yesssss!
Newly discovered invasive fungal something-or-other species is wiping out invasive nuisance “tawny crazy ants” in southeastern U.S.
When tawny crazy ant colonies bump into other tawny crazy ant colonies, they simply merge their colonies amicably, rather than fight for territory as most ant species would do. This has greatly facilitated the spread of this invasive nuisance species – but it also facilitates the spread of this fungal pathogen that has been reducing their numbers and even completely exterminating many colonies.
Sort of like these guys. Uh—gals?
Also blackberries. I call them ‘Kudzu of the North’.
Right. I lived in a rural area in central California for a few years. There were Argentine ants in massive numbers everywhere. Strangely, and politely, they rarely invaded my trailer, and on the one or two occasions when they did, they didn’t stay long. I learned about Argentine ants then – they are basically one big happy colony from pole to pole, just about.
In other good news, it turned out that they just loved to eat Terro ant poison. I put a few baits around, they they glommed onto it. After a few weeks, their numbers were noticeably reduced.
Maybe I shouldn’t have done that. They mostly stayed outside and minded their own business. But they sure were all over everywhere.