Invasive Species

[Northern Light]

We have a Toronto Tree Thread; where we discuss the importance of trees as natural infrastructure to the City; and the issues around natives vs invasives, and growing conditions etc.

But we don't have a thread to discuss the natural infrastructure we don't want.

While non-native, invasive trees are a regular topic in the Tree thread; not all non-native invasives are trees (by a long shot).

So this is a thread to discuss what we need to get rid of, why, how, etc.

I'll start with some recent photos of Phragmites.

Important to say, there is a native version of Phragmites; Phragmites americanus; what I am highlighting below is Phragmities australis, which is the invasive.

While they look somewhat similar, they are quite easy to tell apart in fall, by way of height, the native typically ranging from 3-7ft; while the invasive is 10-15ft tall!

Why they are a problem;

From:: http://www.invadingspecies.com/down.../?wpdmdl=1662&refresh=5f9c6e91ea29f1604087441

For a more practical example of the impact, here is a wetland in Toronto which has been affected by Phragmites:

This is the same wetland, 7 years ago, in fall, before the Phragmites got out of hand:

Note how much lower the water level is today.

This is the back section of the same wetland, currently.

Its supposed to be open-water.

Yes, that is Phragmites where the water is supposed to be.

Both the province and the City have begun to take control measures.

But unfortunately the plant has already established over large chunks of South-Western and South-Central Ontario.

Its going to an extreme pain to get rid of.

 

[old boy]

We have a Toronto Tree Thread; were we discuss the importance of trees as natural infrastructure to the City; and the issues around natives vs invasives, and growing conditions etc.

But we don't have a thread to discuss the natural infrastructure we don't want.

While non-native, invasive trees are a regular topic in the Tree thread; not all non-native invasives are trees (by a long shot).

So this is a thread to discuss what we need to get rid of, why, how, etc.

I'll start with some recent photos of Phragmites.

Important to say, there is a native version of Phragmites; Phragmites americanus; what I am highlighting below is Phragmities australis, which is the invasive.

While they look somewhat similar, they are quite easy to tell apart in fall, by way of height, the native typically ranging from 3-7ft; while the invasive is 10-15ft tall!

View attachment 280081

Why they are a problem;

View attachment 280082

From:: http://www.invadingspecies.com/down.../?wpdmdl=1662&refresh=5f9c6e91ea29f1604087441

For a more practical example of the impact, here is a wetland in Toronto which has been affected by Phragmites:

View attachment 280083

This is the same wetland, 7 years ago, in fall, before the Phragmites got out of hand:

View attachment 280084


Note how much lower the water level is today.

This is the back section of the same wetland, currently.

Its supposed to be open-water.

View attachment 280085

Yes, that is Phragmites where the water is supposed to be.

Both the province and the City have begun to take control measures.

But unfortunately the plant has already established over large chunks of South-Western and South-Central Ontario.

Its going to an extreme pain to get rid of.

There are large sections of phragmites in the culverts of the 401 east of Toronto. If you're driving these routes have a look at how this invasive can and will dominate it's environment if unchecked. I'm not sure what MTO is doing about this. Construction machinery moves this invasive easily to wherever work occurs. I also understand that the invasive plant will hybridize with the native variety. There are groups studying various methods of control . Dog Strangling Vine (DSV) is another nasty invasive.

 

[crs1026]

I'm confessing my lack of knowledge.

When there is a consensus that a species isn't wanted, or has invaded beyond a proper level, how is it controlled or eradicated? Those shots all show natural areas where it would be hard to hunt down each and every plant, and the impacts of tearing it out might also be disruptive or undesirable - erosion, nesting areas, etc ?

I gather Norway Maples are no longer in favour. We have one in front of our house, city-planted, 30+ years old. At the time, it was the species the city was offering for new plantings. I imagine that the planted specimens can be left alone, while in more natural areas it may need to be discouraged.

- Paul

 

[Northern Light]

I'm confessing my lack of knowledge.

When there is a consensus that a species isn't wanted, or has invaded beyond a proper level, how is it controlled or eradicated? Those shots all show natural areas where it would be hard to hunt down each and every plant, and the impacts of tearing it out might also be disruptive or undesirable - erosion, nesting areas, etc ?

I gather Norway Maples are no longer in favour. We have one in front of our house, city-planted, 30+ years old. At the time, it was the species the city was offering for new plantings. I imagine that the planted specimens can be left alone, while in more natural areas it may need to be discouraged.

- Paul

What can and would be done would vary by species, and location.

In the case of Phragmites, which is a wetland edge species (can also grow beside a stream or in a road-side ditch), removal by hand is not impossible, but is very labour-intensive.

There are issues of roots and seed banks, and its not sufficient to simply dig up what you can; you either need to come back and do this in successive years, or you would need, in that scenario to tarp the soil.

Tarping could be done in any event, during the winter (when phragmites dies back), you remove last years dead tops; and then you lay heavy black tarp over the top.

This method super-heats and sterilizes the soil and seeds over time.

This, however, only works for an area that shouldn't have open water (given where Phragmites grows, this is a problem)

There are other alternatives; to be frank, the most common choice if the infestation is large, would be herbicide.

Likely one called 'Rodeo' which is meant for use adjacent to water. (in most cases, pesticide over standing water is not permitted, though exemptions under law can be sought)

There are obviously downsides to the application of herbicide environmentally; but I would argue, with large infestations, its probably the most practical trade-off.

Other options would include excavating contaminated soils and replacing them.

Again, very intrusive. Prescribed burns are also a plausible option, but again, not in standing water.

But the destructive power of this species in a large wetland is substantial.

A full list of management techniques is available here:

https://docs.ontario.ca/documents/2675/stdprod-089643.pdf

 

[Northern Light]

@crs1026

As to Norway Maples.

There is public policy and there is best outcome.

In general, its tough to argue for removing a nice canopy tree on someone's lawn, if its otherwise in good health.

However, Norway Maples, in ravines, and other natural areas are highly invasive and stifle biodiversity, necessary habitat, succession/regeneration of native species, and tend to promote erosion.

The long/short on that last point is that Norways produce very dense shade, and very few things grow underneath one, leaving a lot of bare soil on many ravine slopes.

from: https://torontoravines.org/2016/07/13/norway-maple-acer-platanoides-when-street-trees-break-bad/

That being the case...............we have to consider the spread of seed. Evidence suggests, Norway Maples have a typical seed distribution up to 3km from the tree.

In Toronto, its pretty rare to find a spot where you are not 3km from a ravine or natural area.

In my ideal, we would, systematically remove the trees, over 20 years, beginning w/the ravines/natural areas, and progressing to people's homes that are closest to said locations.

In the real world, City policy would not only not seek the removal of a Norway Maple on private property/public boulevard, but would actively discourage it (on the basis that losing it would be contrary to the City's tree canopy goals).

I'm a pragmatist and that's why I recognize this would be a long-haul move to rid our region of this tree.

However, I don't like the way we manage it now, which is really very selective removal in a small number of natural spaces, typically those targeted for restoration, or adjacent to very high quality/rare habitats.

The problem w/this is that it fails to recognize that more Norway seed will just blow in; and we'll be back to the same problem in a only a few years.

I see that as financially wasteful and ecologically ineffective.

We need to establish core invasive-free zones, and work our way out until there's no further threat.

Lets not kid anyone, doing that with high-priority invasives alone is a 2-generation (40-year project); if we put real muscle behind the idea.

We're a long way from there right now.

Norway Maples in nature need not be removed, only killed.

If there are no home/structures/roads/paths nearby, a tree can be killed and left standing w/o herbicide through a technique called girdling.

For simplicity's sake, its a strategic cut into/around the tree which cuts off the flow of sap and in essence chokes the tree to death.

Its cheaper than felling a large tree and treating the stump w/pesticide.

However, totally inadvisable in a manicured space or anywhere people or structures would likely be endangered, as eventually, the dead tree will fall over.

Needless to say, removals should be accompanied by a replanting (with natives) strategy.

 

[Northern Light]

How apropos.

The weekend I start this thread, the Globe and Mail has published an article on the problems w/Norway Maples.

https://www.theglobeandmail.com/canada/article-how-the-foreign-norway-maple-tree-is-changing-canadas-fall-palette/

Its behind the paywall, but if you can't access it, google, the headline, there are ways to read the whole story.

 

[crs1026]

^Thanks for the education - I understand better.

I am caught between wondering if the problem is solvable - or, like overabundant raccoons and disappearing creeks and Dutch Elms, is it just a sad tradeoff that we humans have irrevocably made as we go, for better or for worse.

I suppose it might be possible to declare an “exclusion zone” around some limited areas (is the GTA just too big?) that is wide enough to defeat natural seed spread. Do periodic intensive and intrusive “seek and destroy” missions in this zone, then take a more measured and calculated approach within the zone. Maybe the ‘preserved’ zones can expand as we go, or become part of urban planning.

However, if seeding and spread is already rampant in the far reaches outside such zones, then the problem may exceed our resources.

Just another example of how the human race is the planet’s biggest liability.

- Paul

 

[Northern Light]

I do think its a challenge we can handle; but there's no question its large and one that would take a great deal of time as I noted.

A ravine with which I am familar, which had severe erosion issues, was dominated by Norway Maple was cleaned-out some years back, by way of a contract with a small logging company that came in and cleaned out all the Norway Maple.

The cost was, in today's dollars, about 45k for a few acres.

The planting budgets as they exist today, are largely adequate to the challenge; of that portion any effort, its a matter how they are focused and executed.

The removals portion would require a good deal more money.

A crude guess, in Toronto alone, would be on the order of about 50M per year, for 40 years. (in addition to current spending)

That sum could address most (not all) invasive species. Certainly all the woody ones. (trees/shrubs).

One thing about Norways in Toronto, as invasive and successful as they are, most mature specimens, as street trees/yard trees have only a 60-80 year lifespan.

The ones lining streets in Leaside are mostly dying now; so not all the trees will require aggressive removal; though homeowners there are still likely to be stuck with expensive take-downs as the trees die off.

In good quality natural areas, just as with any other tree, they can be longer lived.

 

[WislaHD]

I am caught between wondering if the problem is solvable - or, like overabundant raccoons and disappearing creeks and Dutch Elms, is it just a sad tradeoff that we humans have irrevocably made as we go, for better or for worse.

The raccoons are fully indigenous to Toronto

Their overabundance may be due to changing environments, but I do think we have to begin recognizing urban areas as new forms of ecosystems, where species like raccoons and pigeons proliferate.

Which is not quite the same thing as humans accidentally or intentionally introducing non-native species into environment.

 

[Northern Light]

The raccoons are fully indigenous to Toronto

Their overabundance may be due to changing environments, but I do think we have to begin recognizing urban areas as new forms of ecosystems, where species like raccoons and pigeons proliferate.

Which is not quite the same thing as humans accidentally or intentionally introducing non-native species into environment.

If we invested in proper waste management, raccoons would decline in number, and other species would fill the void.

Pigeons on the other hand........are fed by idiots............treating the problem of invasive idiots is much more complex!

 

[afransen]

If we invested in proper waste management, raccoons would decline in number, and other species would fill the void.

Pigeons on the other hand........are fed by idiots............treating the problem of invasive idiots is much more complex!

There are people who feed raccoons as well, perhaps not as common, but it does happen.

 

[lenaitch]

^Thanks for the education - I understand better.

I am caught between wondering if the problem is solvable - or, like overabundant raccoons and disappearing creeks and Dutch Elms, is it just a sad tradeoff that we humans have irrevocably made as we go, for better or for worse.

I suppose it might be possible to declare an “exclusion zone” around some limited areas (is the GTA just too big?) that is wide enough to defeat natural seed spread. Do periodic intensive and intrusive “seek and destroy” missions in this zone, then take a more measured and calculated approach within the zone. Maybe the ‘preserved’ zones can expand as we go, or become part of urban planning.

However, if seeding and spread is already rampant in the far reaches outside such zones, then the problem may exceed our resources.

Just another example of how the human race is the planet’s biggest liability.

- Paul

The success of a concept of creating a buffer or exclusion zone depends on what is trying to be controlled. For wind-borne seeds; likely fairly successful with a fairly small zone, but with pollen, less so (a problem with GMO crops). If the method of seed spread is is animals, it might require a larger zone, If you are trying to constrain organisms with their own motive power it becomes very challenging. Most recently, that was tried to control the Emerald Ash Borer with little to no success.

 

[Northern Light]

On November 20th, the TRCA Board of Directors had before it the TRCA Invasives Management Strategy.

Its a pretty-thin, high-level document.

Nothing wrong with it as far as it goes; but as always, its the funding and the concrete implementation of strategies that matter more.

Strategy here:

https://pub-trca.escribemeetings.com/filestream.ashx?DocumentId=6601

From the report:

A series of photographs documenting different invasive species in the TRCA's jurisdiction (this is not a comprehensive list)

https://pub-trca.escribemeetings.com/filestream.ashx?DocumentId=6602

I may copy some of the photos into their own post later.

Also, an update on a TRCA attempt to control for Phragmites at the Leslie Street Spit: