Author is unimpressed by permaculturalist views of 'invasive' plants

Acacia saligna is considered an invasive exotic in some parts of the world, and is banned or attempts being made to actively eliminate it.

However, acacia saligna happens to be native to my area! So of course it's going to be my number one choice for a nitrogen-fixing medium-term support species. I plant them everywhere, and am ecstatic that I get to use a native for this vital purpose. Obviously it's the best tool for the job for me.

If I had no suitable nitrogen-fixing medium-term support species in my area, I'd probably go looking for acacia saligna due to its invasive qualities telling me it would thrive well. But local natives are of course my first choice.

In my region the most invasive plant is a native - the Ashe Juniper, called Cedar, which used to be confined to small areas when this was all prairie, but with grazing of domestic livestock and no prairie fires, it has taken over and now can form dense "cedar deserts" in which nothing else wants to grow. It's so invasive many people don't even know it's a native. I think it can be a very useful resource for land rehabilitation, if cut down and used to make brush dams in gullies, or brush berms on slopes. It doesn't like to grow under other mature trees or in healthy grassland, so once the damage is repaired, it should be much less of a problem to land managers, though if people don't want periodic fires, it may need to be controlled by cutting periodically.

Mature cedar trees near watercourses are important habitat for the rare Golden-cheeked Warbler http://tpwd.texas.gov/huntwild/wild/species/gcw/

I like to quantify things. On many occasions I have been hired to remove some invasive plant. Some of them are very simple to deal with. Once you pull Daphne out a few times , it's gone.
 
English ivy is another story. On large expanses it may be removed for as little as $50,000 per acre. In residential settings where I have worked , the cost is usually about $3 per square foot. A rudimentary job can be done for much less, but if you wanted me to guarantee that it will not return , that is the amount I would quote.

This isn't theoretical. Look at the pictures below. The garden in question was completely destroyed by English ivy. We ripped out every tree and bush, in order to get at much root as possible. The entire space will be converted to lawn grass for a few years. Once all ivy is gone, a new garden will be established. This was a small garden. Money spent so far works out to about $75,000 per acre. I was just involved in the initial push. The owner will continue until it's eradicated.

Mount Douglas Park has about 200 acres that are covered in English ivy. I would gladly clean up this mess for 10 million dollars. I doubt that they'll be taking me up on this offer, but so far as I know , I'm the only one who has actually worked out a figure.

English Ivy is the devil. We rented a house with English Ivy in part of the yard, and it was always try to smother the trees. I can't understand why someone would plant such a maintenance nightmare in a yard (or anywhere). Ivy, lawns, these things must be remnants from a time when lords could direct their underlings to laboriously maintain landscapes. Did immigrants to the New World fancy themselves lords and try to emulate those manicured gardens?

I am surprized my your difficulty and dislike of Ivy as I have it here in France . I strim it make sure there is plenty of light in the area then I keep cutting with a mower and eventuially it goes away as it cannot compete with grass long term . As for trees I strim it off the bark .

Tyler Ludens wrote:English Ivy is the devil. We rented a house with English Ivy in part of the yard, and it was always try to smother the trees. I can't understand why someone would plant such a maintenance nightmare in a yard (or anywhere). Ivy, lawns, these things must be remnants from a time when lords could direct their underlings to laboriously maintain landscapes. Did immigrants to the New World fancy themselves lords and try to emulate those manicured gardens?

I wouldn't quite go that far, and I think this is a case where we can demonstrate that so much of it is about context.

Where I come from Ivy (Hedera helix) is recognised as an occasional problem in some circumstances, but an integral part of semi-natural woodland ecosystems, where it has truly massive wildlife value. It would very much be a zone 5 plant, but not one to have nightmares about. There is a nuanced analysis here, but it needs to be made clear that this applies to the UK, and probably Ireland and parts of continental Europe, NOT North America: http://www.arborecology.co.uk/article_forf.htm

European rabbits (Oryctolagus cuniculus) are broadly fine and were an important food source for predators in their native Iberia. Here they are a nuisance. In Australia they are a serious problem, partly - but only partly - because of prior damage to the ecosystem by humans.

In terms of introductions my worry involves the risk of getting it wrong. At present I'm thinking about nurse trees. Russian olive (Elaeagnus angustifolia) is an obvious choice, but could be a really bad idea.

This is a fascinating discussion, and I echo the recommendations to read the comment section of the article that began this thread. (You can click here.) There's a bit of flame-throwing and I had to do some skimming (I really am supposed to be finishing up chart work right now!) but the comments in particular are still worth reading.

I think the best description of this argument between some native plant enthusiasts and permaculturalists is "divide and conquer." A small number of people can control a large number of people if they can just get them competing between themselves and/or arguing amongst themselves.

One of the best points I took from the native plant enthusiasts in that comment thread was that sometimes a permaculture writer will recommend a plant that is a terrible idea for a particular spot, probably far removed from the author's experience. The example was hardy kiwi: not an issue on the west coast, can be a problem in New England. It's probably a good idea to have at least one sentence saying "check with local resources" in any articles that advocate pioneer type species. However I strongly agree that when the "invasive" is already present, planting a couple more in zone 1 or zone 2 is not ruining the world.

And, what is invasive is so very location specific. In Wisconsin, variegated goutweed (or Bishop's weed) was triumphant over vinca minor, because it died back to rhizomes in the cold winter and the evergreen vinca took a hit. Just a few hours south, in Illinois near St. Louis (in my mother's back yard), the opposite was true. The snow didn't last long enough to damage the vinca, and the goutweed was shaded out in the early spring by all the vinca leaves already present. Both locations have very similar climates, with random precipitation (summer and winter) and extremes of hot and cold. Only the proportions (how many hot versus cold days) varied, and that made all the difference between the two arguably invasive species.

I am in my third year on a biggish lot in the PNW (by Portland standards - it's just 1/4 acre) that was overrun with blackberry and I finally feel like the end is in sight. After the blackberry was cleared, the perennial morning glory moved in (and boy, does perennial morning glory love hugelkultur!) and the third invasive vine (why are so many of the PNW invasives vines?) that I'm fighting is Sweet Autumn Clematis, which had base vines with 2 and 3 inch diameters when I started. This spring I'm at least at the point that I can just harvest big bags of soft green stuff (from all of those vines) and stuff my tumbling composter with it. When I have more energy (and time) I dig up some of the knobby source roots of blackberry (it's like a pollarded tree, with the knobby part underground) and give them to the municipal composting system. I'm pondering what sort of vigorous plant I can put along the back fence to occupy that shaded space - perhaps a mint? When I was in Wisconsin, a thick layer of wood chips (the free kind) worked well as a place holder and any weeds that showed up in that area were easily pulled, but in the PNW these perennial vines move right in and say "thanks for this great place to run my rhizomes!!"

Neil Layton wrote:
European rabbits (Oryctolagus cuniculus) are broadly fine and were an important food source for predators in their native Iberia. Here they are a nuisance. In Australia they are a serious problem, partly - but only partly - because of prior damage to the ecosystem by humans.

Here the "nuisanse" are wild boars. They ruin corn and wheat fields.

That being said, the wild boars would probably be, on the whole, more valuable than corn or wheat fields. Seeing that people grow corn and wheat and don't make money (excluding govt subsidies), killing 1 boar and taking it to market would probably be more profitable than any number of acres of corn or wheat.

But I'm in the extreme minority here, so whatever.
William

One of my favourite places growing up was a park with all sorts of food trees. It was planted by a recluse about 100 years ago. It had a great diversity of different areas from chestnuts around the edge of one clearing to the deep dark redwood forest. Most of the food plants were European, but there was a great diversity of plants and critters.

I really liked the ivy grove. It was about an acre of woods that had been overtaken by English Ivy that a neighbour had planted in their garden about 40 years before. It smothered trees, brush, and turned everything into a green wonderland. At first glance, it was a monoculture. But it was also a haven for small birds and forest creatures. Insects and orchids grew in the ivy. For some reason, the ivy was fairly self-limiting. It only invaded this one area. Without human intervention, it didn't travel beyond this one acre. I don't know why. Perhaps it was the diversity of the different zones the hermit had created when designing his (what we now call) food forest.

So, yes, ivy did damage to this one area, but why didn't it spread? Was this ivy forest actually a monoculture?


The main complaints about invasive species are that they
1. create monocultures
2. destroy native habitats


I'm not convinced of the first. Perhaps people are playing with the definition of monoculture - comparing invasive species with industrial agriculture perhaps? Only, the monoculture of industrial agriculture and the 'monoculture' of invasive species are very different. Using two definitions of the same word interchangeably like that, is called equivocation. Equivocation is a rhetoric tool - very useful for convincing the masses to believe the 'right' way of thinking... but it does not stand up to rigorous examination.


The second is what concerns me.

From a purely sapiens-centric point of view, I don't want valuable natural resources to be lost because they might become useful to me later. So some action taken towards preserving native ecosystems seems a good idea.

I also worry that hard core conservation is the fastest path to stagnation - which limits diversity - which limits resilience.

A balance seems to be what I want. Careful and correct use of potentially invasive species, but not an outright ban on them. I would rather take the time to educate people that they need to be careful. That setting up a system like food forest isn't necessarily a one-time action. Any natural system is in a constant state of flux, and stewardship of the land takes constant attention and care.

For example, we don't have Kudzu here. I wish we did, as it looks like one of the world's most useful plants. However, I won't start growing it because I cannot devote the long-term attention a system with an invasive like this would require. We may not have the correct environment here for kudzu to become invasive, but imagine we lived in a time with environmental instability. Imagine I started growing it, took every precaution to keep it contained, then had to move suddenly. What if the next land steward didn't understand how to tend their land. What if we soon had a kudzu problem on our little island.

I think there is a problem with invasive species. However, I think this is a problem of human mismanagement rather than any fault of the plants themselves.

I think that permaculture might be a solution to invasive species. Creating checks and balances in a diverse polyculture setting, to prevent any one plant from taking over. Observation (in my opinion the most important tool of permaculture) is the first step to keeping these systems in balance.

Julia Winter wrote:
I think the best description of this argument between some native plant enthusiasts and permaculturalists is "divide and conquer." A small number of people can control a large number of people if they can just get them competing between themselves and/or arguing amongst themselves.

This seems to be saying that a small number of people are trying to control permaculturists. I'm not convinced permaculturists will stop practicing permaculture because some people disagree about natives versus non-natives.

Or is it some other large number of people who are being controlled? To what end are they being controlled?

Tyler Ludens wrote:

Julia Winter wrote:
I think the best description of this argument between some native plant enthusiasts and permaculturalists is "divide and conquer." A small number of people can control a large number of people if they can just get them competing between themselves and/or arguing amongst themselves.

This seems to be saying that a small number of people are trying to control permaculturists. I'm not convinced permaculturists will stop practicing permaculture because some people disagree about natives versus non-natives.

Or is it some other large number of people who are being controlled? To what end are they being controlled?

I would say that permaculturalists and native plant enthusiasts often have the same underlying agenda, which involves living in closer harmony with the landbase.

This threatens the usual vested interests (the small number Julia speaks of). I think native plant enthusiasts are natural allies, but there is a divide and conquer strategy from those vested interests, who are the real enemy.

I recently reviewed Tao Orion's book Beyond the War on Invasive Species (link above). I disagree with her on many things, while I agree with her on many more, but I don't want to lose sight of the real enemy. The main problem, as I see it, with Orion's book, is that her perspective threatens to separate us from those natural allies by de-emphasising native biodiversity.

Those vested interests seek to control everyone and everything not part of their 1% club. Were you not the one who recommended I read Jensen?

Neil Layton wrote: The main problem, as I see it, with Orion's book, is that her perspective threatens to separate us from those natural allies by de-emphasising native biodiversity.

Those vested interests seek to control everyone and everything not part of their 1% club.

This seems to be saying that Tao Orion is working for the 1% or that we here in thread are working for the 1 % because we are discussing (what some people seem to see as disagreeing) about this topic.

Tyler Ludens wrote:

Neil Layton wrote: The main problem, as I see it, with Orion's book, is that her perspective threatens to separate us from those natural allies by de-emphasising native biodiversity.

Those vested interests seek to control everyone and everything not part of their 1% club.

This seems to be saying that Tao Orion is working for the 1% or that we here in thread are working for the 1 % because we are discussing (what some people seem to see as disagreeing) about this topic.

Apologies. No. I think there are differences in perspective even among those of us with related agendas - and I agree with Orion on much more than I disagree with her over. In many ways, resisting the control (as Orion does and as I think everyone else here on this thread is doing) is much more important than the differences in perspective.

I think we need to resolve the differences in perspective, but I don't think we should allow ourselves to become so bogged down in that process that we lose sight of the real enemy.

Neil Layton wrote:
I think we need to resolve the differences in perspective, but I don't think we should allow ourselves to become so bogged down in that process that we lose sight of the real enemy.

Do you think this bogging down is actually occurring? I don't think it probably is, personally. I don't think native plant enthusiasts are going to stop planting and protecting native plants or that permaculturists are going to stop practicing permaculture because somebody wrote an article and some other people discussed it.

I like to think most permaculturists choose to use some native plants in their systems and that most permaculturists don't willy-nilly include invasive species in their designs. I think the permaculturists who want to use invasives are probably going to do it even if people here on permies attempt to discourage them from it. There are some very determined people here!

But overall, if the article and this discussion are a plot to divide and conquer, I think it is a failure.

Neil Layton wrote:

I think we need to resolve the differences in perspective, but I don't think we should allow ourselves to become so bogged down in that process that we lose sight of the real enemy.

Love the Monty Python videos. That's exactly what came to mind when I first read this thread.

Tyler Ludens wrote:

Neil Layton wrote:
I think we need to resolve the differences in perspective, but I don't think we should allow ourselves to become so bogged down in that process that we lose sight of the real enemy.

Do you think this bogging down is actually occurring? I don't think it probably is, personally. I don't think native plant enthusiasts are going to stop planting and protecting native plants or that permaculturists are going to stop practicing permaculture because somebody wrote an article and some other people discussed it.

I like to think most permaculturists choose to use some native plants in their systems and that most permaculturists don't willy-nilly include invasive species in their designs. I think the permaculturists who want to use invasives are probably going to do it even if people here on permies attempt to discourage them from it. There are some very determined people here!

But overall, if the article and this discussion are a plot to divide and conquer, I think it is a failure.

In terms of the discussion I don't think that's part of a plot at all. I think that's us having a more or less sensible discussion on the subject. There are statements with which I disagree, but I don't think it's done any harm and may have done some good. We're looking at an identified problem and seeking solutions. That's constructive.

What would have been less helpful is if we'd got into a fight over it. I think there are things worth fighting about, but I think that would come down to cases, not the generalities we're discussing here.

I am concerned that the original article may have done unnecessary damage - not here, but in others reading it. I have no idea whether that's part of a plot, but I'm inclined to impute poor judgement rather than malice and conspiracy.

Probably.

Tyler Ludens wrote:

Neil Layton wrote:
I think we need to resolve the differences in perspective, but I don't think we should allow ourselves to become so bogged down in that process that we lose sight of the real enemy.

Do you think this bogging down is actually occurring?

Reading the article linked in the OP, I think it is. That article is written from a pro-native species point of view and it directly attacks permaculture for creating monocultures by including non-native species in a food forest. From the author's point of view, that's what's happening.

But really, is attacking permaculture beneficial? Surely there are more damaging agricultural practices that we could spend our time and energy on improving. Is attacking pro-native plant movement a useful endeavour? Surely these two movements are working towards a common goal. If someone had an interest in preserving the current industrial style of agriculture, how better than to weaken the potential rivals by encouraging them to attack each other.

The more I learn of the pro-native plant movement, the more I think permacutlure tools can help them achieve their goals.

R Ranson wrote:
Reading the article linked in the OP, I think it is.

I think you're saying the author is becoming bogged down. I can't see it happening here on permies. I don't think any of us are going to stop practicing permaculture because of that article. So again, if the author is trying to stop permaculture by writing that article and getting us to fight amongst ourselves, I think it is a failed effort.

Tyler Ludens wrote:

R Ranson wrote:
Reading the article linked in the OP, I think it is.

I think you're saying the author is becoming bogged down. I can't see it happening here on permies. I don't think any of us are going to stop practicing permaculture because of that article.

Oh, I see your point now.

Yes, I'm saying the author is bogged down.

I agree with you about permies people.
I think permaculture encourages us to see the bigger picture and how multiple things interact with each other. It helps us to not get too focused on one element of a system.

My thinking at present (and this is something I'm still working on, so it may have changed by the end of the weekend) is as follows:

Non-native species are fine in our gardens (by which I include areas under specific cultivation). Potentially opportunistic species need to be monitored and, if necessary, controlled.

Areas maintained for ecosystem services should be dominated by, if not exclusively include, native species. This supports the biota from the ecoregion in which you live, while providing pollinators etc for the rest of the ecosystem.

Zone 5 is space for wildlife. End of: not someone's private shooting preserve. If a species moves in of its own accord, that's fine: this sort of movement is going to become more common with climate change. Deliberate introductions may be appropriate for species unable to move far or fast enough, or in order to trigger trophic cascade, but this needs to be considered carefully on a case-by-case basis. This is the whole rewilding thing, and is on the edge of topic.

Opportunistic species tending to monoculture may need to be controlled, but without moonscaping where at all possible and the use of pesticides at all.

Note that this is the only time in this post I have used the word "invasive".

Anyone have better ideas?

With regards to "divide and conquer," I just mean that it's a waste of time for native plant enthusiasts to be arguing with permaculturists, we have more in common than we think. I'm not suggesting that there is some sort of plot to make this happen, just that arguments of this sort generate a lot more heat than light, and take energy away from really useful actions, like planting trees!

The only concern I might have is that someone just beginning to look into permaculture comes across an authoritative figure stating that permaculture is bad because it introduces "invasive species" into vulnerable areas. I'm not worried about people who already hang out at permies.com.

Thank you for clarifying.

Julia Winter wrote: we have more in common than we think.

I happen to be a pretty darn enthusiastic native plant enthusiast myself! The only thing it seems to me that native plant enthusiasts in general might not have in common with permaculturists is that permaculturists might be more concerned about where the food comes from, whereas I guess the average native plant enthusiast maybe doesn't think about it much? otherwise they would realize that monoculture is the big threat, not permaculture. So how do we reach out to native plant people to get them to think more about their food?

Tyler, I'm very inspired by the work you're doing including perennial and native plants into your diet. I feel you're a wonderful example of how permaculture and native plant enthusiast can get along. A big thank you for sharing your experience with Sotol. Maybe sharing things like that is the way to get native plant enthusiasts thinking more about food.

Thank you, though I feel I'm very much a beginner and have a long way to go with native food plants.

I've read that autumnberry is an invasive species, but it's been loose in the midwest for over a hundred years and I don't think it's made it to southern indiana yet. So it obviously isn't on the same scale as dutch elm disease. Some folks definition of invasive is dramatically different from others.

During my growing up I picked up a pretty casual disregard for violating laws, unless I was at real risk of getting caught. I also, from the same sources, picked up a real desire to avoid doing something that is going to cause real damage. Because of this, if you can show me that a plant is a danger to the ecosystem or to people, with some kind of scale, (dandelions might be a common cold for the ecosystem, dutch elm disease might by a fast moving, fatal and inoperable cancer). I will be enthusiastic in spreading the news and trying to avoid bringing into the wrong areas. If the best you can tell me is that 'some people, somewhere think this is a problem' I'm not going to take you very seriously. I am a little suspicious of govt. agencies also. I suspect I am not the only person on the planet with anarchistic attitudes like this.

Someone with the requisite knowledge and hopefully a degree of public recognition (note how I gracefully avoided accepting responsibility to be the point man) needs to develop a valid, quantifiable list of invasive species, including wheres, whys and any other potentially useful information. Over a relatively short time, given the lack of such a data base currently, it would probably gain acceptance and have data volunteered by more and more sources, hopefully making it more and more reliable. Putting together the list would be a huge job, but once it was available and advertised, I think a lot of the accidental problems would go away. This is probably the best long term solution I can think of.

I thinking I will write up a suggestion and contact my states department of natural resources about it. If a bunch of states worked together, something good might happen.

Mick Fisch wrote:

Someone with the requisite knowledge and hopefully a degree of public recognition (note how I gracefully avoided accepting responsibility to be the point man) needs to develop a valid, quantifiable list of invasive species, including wheres, whys and any other potentially useful information. Over a relatively short time, given the lack of such a data base currently, it would probably gain acceptance and have data volunteered by more and more sources, hopefully making it more and more reliable. Putting together the list would be a huge job, but once it was available and advertised, I think a lot of the accidental problems would go away. This is probably the best long term solution I can think of.

Europe already has the DAISIE list. See here: http://www.europe-aliens.org/

The problem is that (and this is something Tao Orion discusses) such lists are context dependent and often anthropocentric in nature. To quote their front page,

Alien species can act as vectors for new diseases, alter ecosystem processes, change biodiversity, disrupt cultural landscapes, reduce the value of land and water for human activities and cause other socio-economic consequences for man.

In one sentence they open up a huge can of (New Zealand flat)worms (Arthurdendyus triangulatus).

In this country ivy (Hedera helix), gorse (Ulex europaeus) and broom (Cytisus scoparius) are all useful plants with great wildlife value that can get out of hand here, but that I tend not to worry too much about. Elsewhere any of these plants can be a problem in the wrong habitat. It's all in the context, and the context can be unpredictable until it's too late. There will be species on that list from North America, where such species won't be a big deal, but what might or might not make them a big deal here can be as much a matter of interpretation as the actual disruption of ecosystems, or even the question of whether the species under discussion is merely taking advantage of an already disrupted ecosystem, which might be fine in a managed novel ecosystem created by a permie gardener but another matter if it jumps the fence.

This database might help? https://www.invasivespeciesinfo.gov/unitedstates/state.shtml

It does not have to be invasive to be a problem.
China planted millions of fast growing trees in arid areas.
These fast growing trees also consume much more water than slow growing arid climate trees.
As a result ground water levels have dropped in many of these areas.
Once the ground water is depleted enough the planted trees will die and the arid regions will increase.

Permaculture is just another theory on ecosystem design.
Bad ecosystem design will always be bad ecosystem design.
Good ecosystem design will increase the chances of a functioning ecosystem.

alex Keenan wrote:
Permaculture is just another theory on ecosystem design.
Bad ecosystem design will always be bad ecosystem design.
Good ecosystem design will increase the chances of a functioning ecosystem.

I think permaculture gives us better a chance of good design because it demands we consider elements in relation to each other. Clearly whoever was in charge of the tree planting project in China was not considering the relation of the trees to their environment.

Mick Fisch wrote:
Someone with the requisite knowledge and hopefully a degree of public recognition (note how I gracefully avoided accepting responsibility to be the point man) needs to develop a valid, quantifiable list of invasive species, including wheres, whys and any other potentially useful information. Over a relatively short time, given the lack of such a data base currently, it would probably gain acceptance and have data volunteered by more and more sources, hopefully making it more and more reliable. Putting together the list would be a huge job, but once it was available and advertised, I think a lot of the accidental problems would go away. This is probably the best long term solution I can think of.

I thinking I will write up a suggestion and contact my states department of natural resources about it. If a bunch of states worked together, something good might happen.

The problem with making lists is that invasiveness is so very, very, site specific. When I lived in Wisconsin, if someone had said "I can't believe you planted vinca! That's so invasive!" I would have replied "Not at all, it has barely spread in 7 years and I have to do battle against the bishop's weed for it to even survive." And of course the opposite would be true just one state south.

I think the best advice is "gardener beware," and please check in with experienced gardeners/growers/farmers in your area. It was striking to read Toby Hemenway saying "I didn't know that hardy kiwi is a problem on the East Coast, I've always been on the West Coast" after he'd published Gaia's Garden. (This in the comments section of the article we're talking about.)

I went and checked the text, and there's no warning in there about invasiveness (because it's not invasive in the author's experience). It's described as a great way to shade the house from summer sun but let winter sun through plus provide fruit late in the year for you and wildlife. I was planning to plant it at my place in Wisconsin, on a trellis on the north side of our outbuilding, but never got around to it. I would guess that hardy kiwi isn't invasive on the west coast because there is a long dry period in the summer that it can't survive without some water, and thus some human care. East of the Rockies, the rain comes more randomly, winter and summer, so things are very different.

I have tried for years to get Kiwi to grow out here in the desert... It ain't happening.

This topic is very important where I live, because it is an island with lots of endemics,
that disappeared from the mediterranean in all other places during the ice age.

So they say that plants here cannot defend themselves against what they were not used to.
Especially browsers.
So, this is more than only about plants.

I feel I can import freely all things that grow with water, my watered garden is a green prison for them!!!
No way to escape.
BUT in permaculture, we tend to look for plants that are able to grow with what there is.....
That is where we are a special "danger" in the view of some.

We are "fools" that value resistance over taste and productivity and shelve life etc!!!

In my point of view, an edible invasor is ok, and a pest is not.
Many people use pesticides here, and not before. They are angry at new pests that came by importing goods.

We are still free from some pests of vine and potatoes for example.

About plants: is the opuntia an invasor?
Yes of course but I like it more than local wild plants (almost no edible here!),
and far more than the little acarian that grows on it, the cochinilla.

Are almond trees and chesnuts invasors?
Officially, here they are invasors, yes.
But again, yum!

Aborigenes had only 2 fruits, fig and bicacaro, an endemic that is not a tree.

I think that one of the best ways to control the spread of undesirable plants , is to make it the responsibility of those who introduced it to the neighborhood to remove it from neighbouring properties , if it spreads beyond the boundaries of their own.
 
This has been done in England with Japanese hogweed. The court has forced people to pay for eradication. I read an article where one owner had to spend £300,000. Punishments like this could be further strengthened by eliminating the choice of bankruptcy for those individuals. It would be like having a lifetime judgement against them.

I have warned tenants that they will be removed , should they introduce certain plants.

This island is also lacking in native edibles. Almost everything that we eat is native to somewhere else.

Invasive species do not cover a fraction of the area that agriculture does. Common names are confusing in a discussion which is global, thanks to all who include where the hell they are working! What does "Hardy Kiwi" mean? Which species? Should it be considered agriculture in New England (USA, not OZ) Us humans are not the only vectors: when we team up with air delivery with fertilizer included it can get crazy. I sat under a suppressed Western Hemlock (Tsuga) roost tree one day and counted over 3 dozen English Ivy/Hedera helix seedlings within arm's reach. This species is spreading with exponentially increasing speed throughout woodlands all over the maritime west of N. America. I propose it is time to try a crash program using as a control solution little lambs, altho a kid'll eat ivy too.
Use of stereotypes like Kudzu is not terribly helpful. Here in W. Oregon it was a spectacle on TV news, a Hazmat-suited team of highly paid specialists saving our state from the alien invader, hosing down an ancient kudzu vine with poisons. And yet, altho the USDA was sending free kudzu plants to anyone who asked anywhere in the USA back when, kudzu NEVER became a problem in the NW. Since the US is an importer of kudzu products I would happily farm kudzu if I had it on my place in the SE, and produce fiber for fabric, root starch for organic tempura, leaf protein curd for vegans, and fatten cows and rabbits on the vines as well as use it in my composting systems. People in Oregon are horrified when they find out I actually use gorse and broom (Cytisus scoparia) in my agricultural systems. (I was called "dangerous" by one person because I said on a discussion list that I could work with broom), She, being a paid professional restorationist (altho from what I have seen, not too good at it) does have a vested interest in fomenting invasion hysteria. She boycotted (or should it be "girlcotted"? the permaculture and native plants conference, fearful for her safety, she said) Other people are AMAZED that I don't have a property COVERED in broom because I put it in my compost. HOW CAN THAT BE??? Why do I have the chutzpah to suggest that like Rackham says "undoubtedly broom and gorse were used for fuel in the middle ages, serving equally well to fire pottery or burn heretics" (History of the Countryside) A friend, now long gone, who edited a small unknown journal called "Permaculture and Native Plants" did a test (he was a hearing scientist) where he took a section of an old logging deck along the Siuslaw River where he lived, put a deer fence around an area, cleared half of it of the dense stand of broom and planted the whole to an orchard of dwarf apples. The apples in the mixed zone far out performed the apples in the half which had been cleared of broom. Friends who spent a week of hard work clearing broom on an eroded W. slope above the Tualatin Valley and then planted Chestnuts had all the trees die of over-exposure, but because they had disturbed the ground PULLING the broom out by the roots, had a great follow-up crop of broom. There's a massive industry of organizations recruiting volunteers to clear broom with heavy expensive steel "weed wrenches" on areas which then re-grow with broom. Keeps the supervisors employed. I usually say I "torture " the broom by cutting off branches over time as I use them to mulch the trees I am trying to encourage, so they will understand that I HATE the broom as much as they do. (I love the plant- as one woman who was about to retire from the Soil Conservation Service (and thus didn't give a sh*t) told me: "there is No Better Plant for breaking up hardpan" It is also I know, a wonderfully strong wood, hard and smooth and colorful, even I hear the wood of choice for makers of miniature period dollhouse furniture. I say learn the plant all through, life cycle, properties and propagaton, and figure out what will work. AND OBTAIN A YIELD. And include native plants in ALL your systems. After all, here in W. Oregon, a small area indeed, we have higher endemism than Europe and only 1% of the land has anything like a healthy native plant community left. Most of that loss is caused by agriculture. So here's what I want y'all to do: stop eating the crops which are destroying Oregon: WHEAT, OATS, SUGAR BEETS, Wine Grapes, Hops, Walnuts, Hazels, and puhleze, don't buy lawn grass seed or Christmas trees, OK?

Dillon Nichols wrote: the pine beetle that has killed so much forest that you can't really fathom it except from the air or sat pics...

Where I live the effect of the pine beetle has been to wipe out man made pine monocultures (sort of native but not naturally found in the local area), allowing the oaks, hornbeams, blackberries, wild rose, cornel, plum, wild pear etc. to reestablish.

Agree about Japanese knotweed and other species like it though. I guess it's just a matter of time before a herbivorous insect pest/fungal blight arrives or evolves to attack them.

I'm hearing a lot of blanket statements here, along the lines of "kudzu/english ivy/vinca is bad", rather than "this plant has proved to be a problem in the following areas...."

I remember once discovering that I couldn't buy seeds of Spanish broom in Italy, where it is native, because of a blanket ruling imposed on the world by the US government that said basically "Spanish broom is bad everywhere"

Goats and donkeys love eating ivy especially in winter.

Prof. Alistair Fitter discussed invasives years ago as part of the debate over GM crops and said that as a rule of thumb, 10% of introduced species get into the wild and 10% of those become a problem. He also claimed that it was absolutely impossible to predict which ones would be a problem. It might seem intuitively obvious that a creeping perennial vine which can grow from root fragments is likely to be a problem weed, but the evidence apparently doesn't back this up. Sometimes plants in a new environment evolve rapidly into completely new forms.

The reason for all these vacant niches in a competitive environment is something of a mystery to ecologists. The most obvious factor is that the new species are being introduced without their pests (and we have all heard extravagant claims made for new "messiah crops" which become popular, for a time, for precisely this reason: they don't (yet) have widespread pest or disease problems). another factor is likely to be that humans are changing the environment and creating new niches.

If leguminous trees are taking over, this strongly suggests a problem with the soil, probably man made. In many cases, other plants can coexist well with legumes, the problem may be in our minds. I remember a discussion with a scientist who was researching weed control in peas "do the weeds reduce the yields of the peas?" I asked. "Strangely, no" was the answer. The bible describes tares as a problem weed, but many organic gardeners sow them deliberately

I also remember reading about a guy in Australia who built a cat proof fence to protect rare marsupials which were being driven to extinction by cats and foxes. All cats within the zone were killed. He faced opposition from animal rights groups who deliberately threw cats over the fence (!). Australia's restrictions on animal and plant introductions seem reasonable based on past experience. In other countries it just seems to be about power and control of food. In Britain, there are strict restrictions on imports of food and plants (unless you are a corporation), but there are exemptions for small quantities e.g. a bunch of flowers. In terms of biosecurity this makes no sense at all, but it is in line with rules on tobacco and alcohol, where the motive is financial. I'm guessing that if I attempted to enter Britain with a stray dog from an area where rabies is endemic, saying that it was only a little dog would not help me much.

I ran across this interesting article raising the question of how we decide whether or not a plant is native when the climate is being changed so quickly. With climate change, many species are moving either upwards or towards the poles.

http://e360.yale.edu/feature/how_do_we_decide_when_a_plant_is_native_climate_change/2984/

As this article rightly points out, many species on which others depended are extinct, often due to human activity. That said, I think that does not excuse making the situation worse by allowing invasive species to drive yet more to extinction.

Not all organisms can change their ranges as readily as others. This is one reason we need wildlife corridors, even at a continental scale. Like many others I can foresee a situation where we have a grossly impoverished biota, and the acceptance or rejection of some non-native species may improve or worsen the situation.

I'm really not happy (understatement: "be nice" version) about a situation in which Permaculture is associated with driving species to extinction, even potentially wiping out entire more or less wild ecosystems. I oppose that kind of thing, and am happy to make that clear.

I'm wondering whether we need some sort of redefinition/reclassification:
* Natives (species found in an area before an arbitrary date)
* Species native to the ecozone as distinct from those which are not.
* Organisms changing their range as a result of changes in conditions (i.e. climate change)
* Non-natives from a greater distance (which are more likely to become invasives)
* Invasives, as probably distinct from opportunists (the former tending towards monocultures, and which are more likely to lead to extinctions and/or lower overall diversity)

Note that not these are not likely to be exclusive categories.

EDIT: This paper has a different system, also based on biogeography, which is worth looking at: http://planet.botany.uwc.ac.za/nisl/Invasives/Assignment1/ColauttiandMacIsaac.pdf

One problem is that the question of what even constitutes a "invasive" species is highly nuanced. I, for one, do not want to be associated with taking risks that lead to species extinction, for any reason (I came to Permaculture to get away from that, but I'm increasingly wondering whether I'm in the right place). I also don't want to be associated with a "nativist" movement which is often okay about drenching whole areas in herbicides, and which often has a racist undertone to its rhetoric.

Note also that this says nothing about moving species from one ecozone to another (although it does point out that these are more likely to become invasive). Plants from one ecozone, by definition, are less likely to have functional connections with other organisms in the new ecosystem. They are also more likely to become invasive.

I don't have any reason to believe that introducing a plant to my farm is going to cause another species to become extinct. Even with my most heroic eradication efforts, I'm certain that I have never successfully eliminated even a single species of weed from my farm. I certainly haven't eliminated any weeds by introducing 120 species of non-native herbs and vegetables.

In case I haven't mentioned it lately, all of the flora and fauna on my farm are non-native.

That's fine, but the history of ecology is replete with examples of introduced species jumping the fence and becoming a problem.

Do I really need to spell them out?

We need to be looking at this from a broader perspective than our own plots.

One person's "problem" is just another plant to a pragmatist like me... I have hundreds of species of weeds growing on my farm. It is impossible for me to identify most of them to even what family they belong to. Without an identification to the species level, it is impossible for me to look up on a list whether they are a wicked foreigner or a saintly native. I can't tell any different between them in growth patterns, or in ecosystem services that they provide to the other species on my farm. In other words, it is pragmatically impossible for me to be able to know which plants are allegedly native, and which are purportedly foreign. I can't, with my own eyes, observe any plant or animal "destroying" an ecosystem, or destroying my farm. I just see plants. Some are annual, and some are perennial. But they are just plants/weeds. No problem. My vegetables and herbs would be weedy even if there were not hundreds of other species growing on my farm. So the pragmatist says that since it's impossible for me to know, there is no point in stewing about those things that are impossible to know.

All life is precious to me, and is welcomed on my farm.