What to do with invasive species in dunes

Hello!

I love reading this forum so I am happy to create my first thead.
My question is what to do with 3 invasive species that have overrun a property near the dunes, in Sintra Portugal.

So the main invasive species are the following:

Acacia longifolia

Arundo donax

Carpobrotus edulis

The initial plan is to ring bark the Acacia trees and cut the giant reed (knowing that they will just regrow if you do not remove the roots as well).
We also talked about covering the cut giant reed with a thick sheet of black plastic to kill the roots. The ice plant (Carpobrotus ebulis) is going to be the biggest challenge because of the area coverage. The strategy for this one will be to pull the plant with the roots out of the ground.

The end goal is to then introduce native dune species instead. But at the moment these 3 species out compete everything else.
I am putting my question here because I would like to see if there is a more permaculture way of dealing with this issue other then just physical removal of the plants.
I remember reading an article about invasive species where it was stated that the best way is to understand the soil conditions that these particular species thrive in and then change it so that they cannot survive.
My issue with this is that I do not know how to change the soil to kill these species AND allow other native species to thrive .

Thanks in advance and happy holidays to all

What type of soil is it and will removal of these plants lead to erosion ? Any pictures of the site ?
Are these plants part of a natural succession leading to eventually their own downfall ?
David

Hello David,

The soil is very sandy as the land is a dune. The removal of these plants will surely lead to erosion. But like I said the plan is to introduce native dune species after the removal.
These plants in their native habitat lead to natural succession, but in this enviorment they will overrun the whole area and I found no evidence that this will change in the next 20 years.
I leave in attachment the picture of the property.

Can you identify any conditions that have changed at your site before these 3 new species had managed to establish themselves?  Usually the plants with a long history of living in an area are the best adapted and fill the available niches, but if the conditions change then they may no longer be doing this.  Has the climate shifted....the amount of rain and temperature?  The soil pH changed?  Land use pattern changes?  Are there new disturbances or the elimination of previous cycles of disturbance?  If you can identify what the conditions were that led to the natives flourishing and can return the site to that set of conditions then the natives might dominate again.  If you cannot have conditions that favor the natives then after all your work to rid this spot of the exotics and reestablish the natives why would the exotics not continue to return over and over again?  You will then be in a battle against nature forever.  

I wish you good luck....some changes in conditions can be addressed more easily while others are very difficult.  

Thank you Greg.

You asked me a series of very pertinent questions that I haven't thought about before.
Understanding how the land was before and what led to the current situation is very important information.
I will meet with the supervisor of this ecological restoration project and ask him.
I do know that he has done several test with native species but unfortunely most have failed.
It could be that the current species have made the soil to acidic and now very little species can survive.

You are very welcome!  If you can, please read the book "Beyond the War on Invasive Species: A Permaculture Approach to Ecosystem Restoration" by Tao Orion.  Tao has been involved in ecosystem restoration as well and she has brought permaculture principals to these efforts.  She has very helpful insights into the dynamics of ecosystem invasions that are often lost when the focus is strictly on the invading plants and not on the environmental changes that set the stage for the shift in plant population makeup.  I very, very highly recommend this book.

Guilherme Weishar wrote:Hello!

I love reading this forum so I am happy to create my first thead.
My question is what to do with 3 invasive species that have overrun a property near the dunes, in Sintra Portugal.

So the main invasive species are the following:

Acacia longifolia

Arundo donax

Carpobrotus edulis

The initial plan is to ring bark the Acacia trees and cut the giant reed (knowing that they will just regrow if you do not remove the roots as well).
We also talked about covering the cut giant reed with a thick sheet of black plastic to kill the roots. The ice plant (Carpobrotus ebulis) is going to be the biggest challenge because of the area coverage. The strategy for this one will be to pull the plant with the roots out of the ground.

The end goal is to then introduce native dune species instead. But at the moment these 3 species out compete everything else.
I am putting my question here because I would like to see if there is a more permaculture way of dealing with this issue other then just physical removal of the plants.
I remember reading an article about invasive species where it was stated that the best way is to understand the soil conditions that these particular species thrive in and then change it so that they cannot survive.
My issue with this is that I do not know how to change the soil to kill these species AND allow other native species to thrive .

Thanks in advance and happy holidays to all

Of the three, the ice plant will be the hardest to get rid of.  Sea Oats might work since they can rise above the ice plant and their roots go deeper and will thus undermine the roots of the ice plant.
If you can get some allopathic plants established, they will go a long way in eradicating these invaders.  You can drill holes in the trunk remains of the Acacia and use fungi spore water to get those to rotting, that will end with the roots dying and rotting.
Epsom salts dissolved in water and poured in a localized area will help change the pH for a while and as it leaches down it can do damage to those roots as well.
Definitely talk to your local expert, they will know methods that work that will fit into a restoration project.

Redhawk

There's another book I can recommend: were do camels belong? And there are some really good threads here discussing native/ invasive.
Be careful what you are doing and at least there is something growing, weather invasive or not, mother earth does not care.

On my farm, I consider every plant that is growing in the wild-lands to be a native plant. Doesn't matter to me if it has been growing here for one season, or 500 years, or for millions of years. If it's currently growing on my farm, I consider it to be a native, and I welcome the contribution that it is making to the web of life.

From a purely pragmatic standpoint, 15,000 years ago my farm was covered by several hundred feet of water. Therefore, every species of plant that currently lives on my farm, is non-native.

I would look into that will eat these species. Is there some sort of livestock that would eat these species? I have recently heard a lot about using sheep and goats to control invasive weeds. This can produce a profit from some invasive species.

Are there insects that prefer these species? Insects cannot eliminate an invasive species as their population depends on that species bring present but they can weaken the plants enough for other species to grow.

Thanks everyone for their contributions and sorry for the delayed reply (I turned off email notifications).

So I have talked to my local supervisor to understand the land a bit better.
When this plot of land was bought it had a house in ruins. This was then demolished and the rubble was spread across the land. Sand was imported to cover the rubble (still need to figure out how thick is the sand layer).
All in all this is terrible soil. My supervisor is talking about making a food forest, a veggie garden, a herb garden, etc..
But with this soil it seems impossible. Importing soil is out of our budget so he says we could create new soil by progressive mulching over years. To create 1 inch of soil it takes about 10 years and this is with consistent mulching through out the year. So I am not sure if this is realistic, maybe somebody has some experience in recovering very degraded soil?

In conclusion I am losing faith in this project. I am hired for one month to clear the overgrowth along a wall, because the neighbour complained and threatened to pursue legal action.
The plan would be for me to implement permaculture systems afterwards but the more I think about the situation the more I start to believe that the current state is not that bad considering the poor quality soil. I mean its a mini jungle out there. A jungle with a very low biodiversity, but at least there is something. Removing everything seems so pointless and risky because whatever native species my supervisor wants grow might not survive. Any feedback on my dilema is much appreciated

I'm totally unfamiliar with that ecosystem. But even with a grainy, low-resolution photo, I think that I can identify a dozen species of plants living there...

If you want to see what might do well in the area, take a hike. Pay attention to the species that are growing in similar areas. Propagules from them might thrive on the land you are stewarding.

Thanks Joseph for your input. I did take a hike and I saw several other species around. But the most prevalent are the 3 species I mentioned. Among the Ice plant there are other species such as Oxalis but not much more. I think a good strategy would to replace these species with native ones that behave the same way, this is a suggestion from the book "Beyond the War on Invasive Species: A Permaculture Approach to Ecosystem Restoration" by Tao Orion

I don't understand the allure of ripping apart a perfectly functional ecosystem in order to attempt to replace it by a pre-historical ecosystem that we don't really understand all that well. Species come and go on a regular basis in every ecosystem.

What's the point of fighting a tide? That pre-historic ecosystem is gone. It cannot be restored and maintained long term. Mother nature's budget is much larger than puny man can hope to aspire too.

Supposing that you gathered those giant reed plants, and made a pile of them about a foot thick somewhere on the property? They would decompose and make excellent soil for whatever you plant in that location in future years.

Maybe the best idea is just to crop and drop , again and again :-) lets see what happens , eventually nature will out .
Maybe plant a couple of trees keep on cutting and dropping Sometimes we have to go at natures pace and trying to fight nature is just not worth the cost

David

Is the intention to try and restore some form of pristine ecosystem? Or is to make the land productive for growing food?

If the latter then you need to be prepared for a long term, and on going, slog of soil building. I would focus on intensive soil building in some limited beds for cultivation. Perhaps consider some small scale terracing to make level beds, and add plenty of biomass to those beds as mulch. Joseph has already suggested deep layers of rushes, which would probably work well, and could be pulled apart for planting through.

In addition, you might also look into biochar. Mulches break down rapidly, and it is a continuous process to keep on building soil organic matter. Biochar, on the other hand, can be added incrementally as it is available and persists in the soil indefinitely. It holds nutrients which would otherwise be washed through the sandy soil, and can hold moisture during dry spells.

Google tells me that your climate doesn't suffer from frosts. If you need to stabilise sandy dunes and have a source of mulch then you might consider using vetiver. It is a non-native clumping grass that sends down really deep roots.  When cut, the leaves make an excellent mulch for beds and other plants. They trap wind blown sediment and can provide micro-climate niches to protect vulnerable plants from strong coastal winds.

invasive usually means that it grows fast in the environment. Since your soil is so terrible, why not put these immigrants to work building organic matter in the soil using a regular chop and drop regime?

Guilherme Weishar wrote:... he says we could create new soil by progressive mulching over years. To create 1 inch of soil it takes about 10 years and this is with consistent mulching through out the year. So I am not sure if this is realistic, maybe somebody has some experience in recovering very degraded soil?

My experience is that mulching creates good soil very quickly, within one year, but my bad soil was different from yours so the results may be different. I mulched on absolutely barren desert ground, and watered with greywater from my kitchen that added nutrients, and my soil improved amazingly, within one year, and continues to improve. The first year, I buried some big dry rock hard chunks of cow dung in it, watered with greywater, and occasionally dug it to mix it up. For the 15 years since then I've been planting continuously into the mulch, and soil just gets better and better. Occasionally I added a little "liquid gold" to the greywater container. The first year I went out and collected mulch of dry stems and stalks from the sides of a stream in winter, and I brought in a little bit other times, but now the stems and stalks from my own vegetables and ornamentals produces more mulch than I can use, and I have a pile in the corner to be used later.