I’m curious if anyone knows of examples of introduced/alien species that have naturalized into ecosystems without becoming invasive–especially if they’ve been in any way beneficial to their new ecosystems (not just beneficial to humans via for instance agriculture). I’m thinking, for instance, of non-invasive species that might have helped reduced toxins in the air or soil, reduced invasive species numbers etc without any sort of significant backfiring (from what I understand, backfiring has happened at times when conservationists have introduced species in an attempt to control invasive species). I recognize this is a complex topic often without easy answers but would appreciate any sort layperson-accessible relevant insight. Also any links to literature that explores this topic more would be great too. Thanks!
Absolutely! In North America, plantain is a great example. It’s a good medicinal plant, and it stays low to the ground. And clover fixes nitrogen.
Pacific oysters in the North Sea were first thought to be highly invasive, outcompeting native mussels like Mytilus edulis, but actually, the oysters benefit that species and a lot of others by providing hard substrate in an area otherwise completely covered by soft and often very fine sediment. Mytilus edulis can grow older and bigger on oyster-shelfs (idk if it is the right word in English?) than on other individuals of its own species due to not being pushed into the sediment by the weight of younger mussels attaching to it.
I wouldn’t be surprised if they had a positive impact on biodiversity of that region this way, especially for sessile filtration feeders.
Yes there are non native plants that are not invasive. But almost always they are not benefiting ecosystems though there are some rare examples.
oksanaetal mentions plantain, but there are native plantago species that have a niche similar to the one the non native occupies. The medicinal properties that people seek can be found in native plantago species.
Clover was also mentioned, while most of the common clovers are nonnative and invasive in some parts there are native counterparts that fill the same niche and fix nitrogen.
Even if a non native is doing a good service, like some people like to defend some non native plants saying their berries feed the birds, they almost always are replacing an existing native species that does the same thing.
Another example being honeybees, yes they do pollination, but so do hundreds of other more important native bees.
It is helpful to not think about non natives from a human perspective of what services are they offering but from an ecological view.
I would think most introduced species are not invasive. We only know/hear about the ones that are invasive/problematic. And just because something helps in some way doesn’t mean it’s not still invasive or problematic.
For example, spotted lanternflies pose big problems for the grape industry, but they might actually be helpful in killing Ailanthus.
(I’m guessing this is what we call oyster reefs.)
We have biocontrol on invasive species - does that fit your question?
https://www.inaturalist.org/taxa/569133-Dasineura-dielsi
Deliberately introduced, and having some good effect.
Or did the same thing. The Asian clam is thought to have saved some endemic turtles from extincltion by becoming their new prey base after native freshwater mussels became rare for other reasons.
An interesting one is Monarch Butterflies in Australia. They feed on the invasive milkweed plants. I haven’t heard of any negative aspects of their presence, but some people do label them as invasive. I actually see more here than I did back in America where they are native.
The use of Inga edulis in reforestation is becoming common. It is native to northern South America but does not cross the Darien in Panama (I think). In Costa Rica, where I work, its closest parallel is Inga oerstediana. I. edulis grows faster, produces a more regular seed crop, and is better able to tolerate the invasive pasture grasses that are so common in rural parts of the country. Even in coffee plantations where it is used as a shade tree, it does not appear to reproduce well at all and, being a tree of open areas and early secondary growth, will eventually be shaded out as other species come to dominate.
From my own work, it also seems to have a greater ability to fix nitrogen in heavily degraded soils. I have areas where you can see a green ‘shadow’ on steep hillsides that extends downslope from clumps of E. edulis. This results in other species having accelerated growth when planted in proximity to E. edulis. I have slopes that have been grazed for more than 60 years where it is the only species that shows any growth even after 4 years.
All that being said, it is the only non-native species I use and I consider it a tool in environmental restoration more than a long-term member of the forest assemblage.
The weird thing about monarch butterflies in Australia is that the host plants Gomphocarpus spp, were accidently introduced from North America where they are weeds of minor importance. Monarch butterflies first appeared in Australia in the 1870s. There is no record of them being deliberately introduced. DNA analysis also indicate that all the monarchs in Australia are closely related. The accepted theory is that a gravid female monarch must have flown, or was carried by winds across the Pacific Ocean from North America where she would have found a ready food source for her caterpillars and no natural predators. Monarchs make a long distance migration every year from the US and Canada to Mexico so no one doubts there abilities to fly long distances.
Thanks for answering! Yes my interest is exactly around the examples of introduced species’ beneficial impact on ecosystems, not just from a human perspective. Or at least introduced species that integrate into an ecosystem without becoming harmful/invasive/replacing native species.
Interesting thanks for sharing! When you say you consider it a tool in environmental restoration more than a long-term member of the forest assemblage do you mean that you don’t think the E. edulis will survive for long in the new ecosystem or just that it is being used for the single purpose of restoration?
Meaning I do not expect it to survive when the forest ages from early secondary to late secondary. It does not have very good shade tolerance and does not appear to be a long-lived species. JMO but I think it will all be dead in 20-25 years with other native species taking its place.
I should add that it wouldn’t be unreasonable to cut them if they were having unforeseen affects. They account for something like 15% of the trees we’ve planted so it’s not unmanageable.
Hmm. If they truly flew on their own i’m not sure they would meet all the criteria for invasive anyway, depending on the definition, but this stuff links to a lot of semantic arguing.
What i want to know is… do the monarchs in Australia migratE? In California some of them started roosting in Eucalyptus after native sycamores were reduced in numbers by development, etc. Do the ones in Australia also like Eucalyptus?
According to this article https://en.wikipedia.org/wiki/Monarch_butterfly_migration Monarchs in Australia and New Zealand only migrate for short distances. I am not aware of monarchs roosting in eucs but would not be at all surprised if this was the case. At the back of my house I often see monarchs roosting in Melaleuca spp. Melaleucas are of course a virulent invasive species in the US, in particular the Florida Everglades.
It depends, as @thomaseverest mentioned, most introduced species are not invasive. For none-invasive introduced species, the human perspective is a legitimate view. Most crops are non-native in most areas where they are produced, but they might be a more effective food source than the native plants, which might perhaps allow a reduction in the overall area needed to produce food, and will most certainly reduce emissions through shorter transport distances.
Personally, I feel like it is unhelpful to label all natives as automatically good and beneficial and all introduced as automatically bad/not beneficial and unrealistic to keep everything as it is. What we need to do is limit the rate of change caused by humans, not eliminate it all together. If an introduced organism finds a free niche, and doesn’t outcompete any other organisms, then so what?
Edit:
For example: Established populations of Psittacula krameri in central Europe
They live in cities, their impact on native species (plants and other birds) has been studied well. They do not damage trees, they do not outcompete or replace native species (only negative impact is that they reduce the number of nesting spaces for Sitta europaea in cities, where that species doesn’t really live anyway, so the effect here is negligible and has no effect on the population size). However, due to their habits of cleaning and upgrading their nests has shown to have a positive impact on available nesting spots for other native birds in the next year.
I think the danger is when people decide "some non-native species may be beneficial so i should try introducing one i think is beneficial’.It’s a common belief in some permaculture circles for instance, that invasives are actually good and it benefits permaculture to spread them around. It’s damaging. it is important to consider the effects of invasive species. For instance, i’ve observed that glossy buckthorn, when compared to common reed and the invasive strain of reed canary grass, has much more native herbaceous species in the understory. For that reason i suggest prioritizing controlling common reed and reed canary grass, and only being concerned with glossy buckthorn if removal doesn’t cause a lot of other damage and is fairly easy, or all other inavsives are eradicated. Certainly i don’t recommend anyone spraying a bunch of pesticide to eradicate a few dandelions (pesticide is a whole othr can of worms but i won’t get into broader discussion about it here). I do think it’s also worth considering urban ecosystems differently like @eyekosaeder just said. A dense Euroepan city core isn’t a native habitat, and while it was at one time, it hasn’t been for a long time. Parrakeets that live in that eivnronment, or pigeons, rats, dandelions, etc, aren’t displacing native species usually and aren’t in a habitat where really anything is native. So i don’t see them as a problem if they don’t stray from urban areas. Some of the parakeets in Los Angeles do roam into city-adjacent natural areas in pretty dense flocks, so they may be more of a problem. But maybe not, i don’t really know.
I’d actually consider those both invasive. While they do have some benefits they often grow extensively enough to be crowding out native species.
Anoles in south FL. They mostly utilize unnatural suburban habitat which isn’t used as much by native anoles.
but only because native green anoles have a camouflage disadvantage in urban habitat over the non native brown (cuban) anoles, so no I wouldn’t say they are benefiting an ecosystem but taking over a new niche due to an advantage