SCIENTISTS: Sometimes Invasive Species Are Good

[webmaster]

There's a report in Wired about a new study that concludes we should be more open-minded toward non-native species. The scientists goals are to "encourage a more open-minded consideration of benefits..." of invasive species.

[quote]In California, for example, native butterflies feed on non-native plants. In Puerto Rico, alien trees help restore abandoned pastures to a condition suitable for native plants. Even the much-maligned zebra mussel helps filter toxins from lakes.

“We predict the proportion of non-native species that are viewed as benign or even desirable will slowly increase over time,â€

[rainbowgardener]

I think there are cases where non-native butterflies and other insects can feed on alien plants, but usually that is when they are a very closely related species to something native and even then it doesn't always work. And butterflies are not the best indicator. Adult butterflies will take nectar from any nectar bearing plant (e.g. butterfly bush). But if the suitable native plant to feed their larvae is not around, no next generation of butterflies!

What we are most concerned about is herbivorous insects, leaf eaters. Surprisingly enough to most gardeners, herbivorous insects are very necessary in the garden/ ecosystem. They are the basis of a food chain, they bring the predatory insects that we want to have [eg the brachonid wasps that control the tomato hornworm] and they feed birds.

Herbivorous insects are very sensitive to the biochemicals in the leaves. It turns out that all plants have built in chemical defenses to help prevent them from being eaten. Over [LONG periods of] time, insects that co-evolve with them develop resistance to the defenses and can eat them. Doug Tallamy, Bringing Nature Home, says "a plant that isn't being eaten, isn't doing its job [in the ecosystem]." Things that didn't co-evolve with the plant, can't eat it. Norway maple has been in the U.S. for 300 years and STILL none of our native insects can eat it....

It is a very complex problem, because basically we have already lost the war against alien invasives. Mile-a-minute weed, kudzu, and many others are probably here to stay. It's very hard to stuff the genie back in the bottle. But I believe we HAVE to protect our native species. The trouble with the invasives isn't so much that they are here, but that because they have been taken away from their own native ecosystems, where there were built in biological controls for them, they so much out compete all the natives. Alien weeds degrade ecosystems, turning them from living, diverse webs supporting a huge variety of insects, birds, and other wildlife, to dead monocultures, supporting nothing much but themselves.

If the Japanese honeysuckle shrubs were not so aggressive, they might be nice plants (I imagine they were in Japan originally), green a lot of the year, fragrant flowers, pretty red berries. But notice that the red berries last forever, because our birds won't eat them. And when the honeysuckle takes over the woods, all the spring ephemeral wildflowers die. Spring ephemerals need that window of sun when spring starts but the deciduous trees aren't leafed out yet. But the honeysuckle leafs out so early and densely, the ground is too shaded too early. Bye-bye spring ephemerals and all the things that depended on them.

[webmaster]

Have we really lost the war?

In California we're battling the zebra mussel. At many lakes boats have to pass an inspection before they let them launch. I was surprised by the following statement in the article:

Even the much-maligned zebra mussel helps filter toxins from lakes.

It also filters out the base of the food chain, initiating a collapse in the fishery.

[Pineville]

This is an up-and-coming argument with the sustainable landscape community and native plant proponents.

I think the arguments against the use of non-natives are clear, and have been voiced for years. However, it may be helpful to consider all of the other environmental factors for a community of plants to survive; global warming and changing weather patterns, damage to plant communities from over-browsing deer, pollution, and other man-made events. We have created most of the environmental problems on our planet, and now we need to manage them. I don't believe promoting the use of exotic invasives is the answer to our decline in native species, but NOT considering non-natives is, in my opinion, short-sited.

[tomf]

Rainbow as always you are very insightful.
Scientists have done fossil studies on extinction rates and come up with a natural rate of extinction. This rate does not include sudden extinctions like the meteorites that wiped out the dinosaurs. After the rise of humans and our populating all parts of the world the extinction rate now is one thousand times the natural rate of extinction. Some of this is due to habitat loss, some of it due to pollution but most comes from us bringing non-native species in to environments that they do not belong in. Now global warming may play a part in adding to extinctions. Perhaps there will be a migration of southern plants north but I do not see bringing them in from other places as a good idea, humans are to dumb to know what we are fully doing. I could be wrong on a few plants but I do not know enough to say.
Out here some woods are being over run by English Ivy; it chokes out trees and kills them; I know of no animal that eats it. There are a number of other plants that are invasive here as well. There may be some cases where a non-native is a good mix with natives but I think they are few and their impact upon the environment they are introduced to must be well understood. Many of the extinctions are in animals as we have brought animals into places where they are not native and they kill or replace the native animals; this also affects the plants as some plants get over feed on. Insects introduced into environments where they have no natural predators or in some way throw off or squeeze out the natives have been a very big factor and could affect our food supply as well. At the very least all this non-native introduction of spices throws off the natural balance.
All most all of us have some non-native plants in our yards but I stay clear of invasive plants and I let most of my forest remain natural; I have only done landscaping on the acres near my house and much of it was done to encourage wild life. I remove invasive plants and in some cases thin some trees or make fire roads on the rest of the land.

[rainbowgardener]

"and I let most of my forest remain natural; "


I appreciate your good stewardship of your land. Unfortunately in many areas it is no longer enough to let forest stay natural, because of the influx of invasive exotics. We have to actually work against them to save any native species.

My Meeting (church) owns five acres of woods in the middle of the city. For the first couple decades we owned it, we thought it was enough to let it remain natural, all we had to do was not bother it and it would be ok. Unfortunately not true, a least for a little patch of woods in the city. It became over-run with Japanese honeysuckle, English ivy, vinca, euonymous, etc. In the past few years we've been working to try and restore it, but it's a pretty heart breaking task.

Today I was going to take someone on a wildflower walk, because I have walked those woods for thirty years. It turned out to be a tour of where the wildflowers used to be: "this area used to be a field of appendaged waterleaf, when it was in bloom it looked like a blue cloud... this area used to be full of solomon seal ... I remember sitting here and sketching the virginia bluebells ..." There used to be trilliums, jack in the pulpits, false solomon seal, wild ginger, trout lily, may apple, camassia, dutchman's breeches, squirrel corn, and a number of others. Now if you look very closely you can find little remnants of some bravely poking out of a sea of vinca. Some of it appears totally gone. And it's been an on-going process, even though there was a lot of ivy and vinca decades ago, there was a lot less of it and a lot more wildflowers. Year by year the wildflowers have been choked out more and more. Ten years ago there were still a lot more wildflowers than now.

In the past few years, we have been working hard at removing honeysuckle (so tree seedlings can come back... the canopy was dying out because big old trees weren't being replaced, the tree seedlings get choked out too) and a lot of the vines growing up the trees. We haven't much tackled the vines covering the ground (yet) being a daunting task. But there is a ray of hope. We pulled all the vines off a big old tree and cleared an area maybe two feet out from the trunk in all directions. What do you know, a may apple popped up in the cleared area, though they haven't been seen there for a few years! Made me cry to see it! So I guess there's still some seed reserves in the soil and it can come back if we give it a chance.

But clearly if we hadn't started actively working to save and restore it, there would be no native wildflowers left at all in a few more years.

[PreserveFlowers]

I think non native can be helpful but I don't know that we need to concentrate on it.

[rainbowgardener]

You are having fun resurrecting a bunch of old threads, PreserveFlowers!

This was an interesting one. Clearly non-native can be helpful - much of what is in our veggie gardens is non-native.

However, this is somewhat a sore spot for me right now, as I am just back from spending a week volunteering with 20 Sierra Club folks working to remove invasive foreign species in the forest at Mammoth Cave National Park. We pulled close to 500 large garbage bags stuffed full of garlic mustard, but all we did was a small area around the visitor center, entrance to the caves, and beginning of a main trail. We didn't touch the rest of the 54,000 acres of the park.

The garlic mustard stays green much more of the year than the native wildflowers and it grows really thickly and chokes/shades them out. Where the garlic mustard grows, pretty soon no more wildflowers. The garlic mustard is actually edible (it was brought to this country a long time ago as a pot herb). But if you mean your name PreserveFlowers, you shouldn't be too excited about having all the wildflowers wiped out of all our forests, in favor of a rather ugly pot herb. Humans can eat it, but I don't think any of our native birds and insects do.

I do believe what I said above, that we have already lost this war and our beautiful forests are doomed. I did a service trip last year in the Tahoe area, California. They are battling to save their spruce trees from some imported orange fungal disease that I don't remember the name of. And there are pine borers and gypsy moths. Here at Mammoth Caves, besides all the invasive species (we also spent a day cutting privet hedge), the dogwoods are being wiped out by anthracnose fungus, the hemlocks have an insect killing them, the ash trees are being wiped out by the emerald ash borer, the fresh water mussels in the river are being wiped out by a little Asian clam that multiplies in the billions....

If you like forests, go walk in them now and take lots of pictures. In 10-15 years there won't be much left. I try to console myself that eventually nature will come to some kind of new balance. It will look a lot different than the old one, but it won't be forests composed solely of garlic mustard, English ivy, privet and honeysuckle. But that's a process that takes many thousands, if not millions of years, so it is some what cold comfort.

[Wilburos]

It's good to resurrect! I can't really jump on the non native species are bad bandwagon! Every plant or flower I look up - eventually in the description says originally from Japan. Even Azaleas, and Crepe Myrtles. When I shop each spring for plants and flowers, at the nurseries, you can only buy what is for sale right? As in, most of those plants are not native. Just where are we supposed to get the native plants at if they are not selling them? We are stuck with the cultivators fancy of the moment. How can you be against non-native when plants and flowers are cross bread so much that they lose their originality? Hibiscus being bread to survive in cold climates. Pansies having originated form violas. My yard would be bare if I had to stick to native species!

[rainbowgardener]

"my yard would be bare if I had to stick to native plants."

Not so... you just have to try a little harder, be more thoughtful, and not shop at big box stores. The big boxes I don't recommend for plants anyway, since there plants are factory produced, not well cared for once they arrive at the store, and their staff know nothing about their "products."

For Maryland check out:

http://www.mdflora.org/publications/nurseries.html

http://mastergardener.umd.edu/files/Nat ... rch071.pdf

or of course the many on line native plant nurseries.

Check out Sara Stein's wonderful and very readable books Noah's Garden and Planting Noah's Garden or Doug Tallamy Bringing Nature Home, for why this is important.

[rainbowgardener]

of course I meant "their plants." This is another of the threads that won't let me edit.

[WildcatNurseryman]

Rainbow, I feel exactly as you. I believe the war was lost long ago. The first pig to set foot on our(their) shores doomed the natural flora and fauna. It is a depressing subject especially when you visit the Eastern part of the State. I get really excited by the flat fields of some crap-ass grass, butterfly bush, royal paulownia and general crap that the "reclamation" left on most any mountain/now plateau. It's so much nicer than the natural geography/fauna. Just ask any coal-miner.

[Ornery_Pony]

Some non-native species are good but overall I have to agree with the other posters that they tend to cause more trouble than not, for the reasons already stated on this thread. About half of our dozen+ acres are natural woodland and is backed by another 100 acres of woodland and pasture. For the most part it is unspoiled but I did find English Ivy growing in some places of my lower horse pasture in the wooded slope. I was telling my son how we should pull it out and destroy it so it doesn't take over everything. It is left over from a cabin that used to stand in those woods long before we purchased the property and we have been digging up daffodils and other non-natives that I have moved to my own garden. I also have Nandina planted along one side of the house that was there when we moved in. It is very pretty, especially in winter and hte birds love it, and I like it too, but...

Now I have noticed little nandina bushes sprouting up around in the woods near to the house. They add a nice splash of color but I have none-the-less been pulling them up. I intend to pull up the rest of them shortly. I don't mind the few up by my house but the birds do spread the seeds so I must control the invasive volunteers. I would like to remove the nandina entirely and replace with azaleas when I have the budget to do so.

I did get a surprise volunteer a few years ago. An Oregan Grape Holly has sprung up by one of our woodpiles! Some bird must have pooped out a seed and now it's a small, attractive bush. I am keeping an eye on it though because while it's technically a native of North America, it isn't native around /here/ to be certain. If I see any more of them popping up I will have to move it to a planter and destroy seedlings. So far though it's been there a few years and I haven't seen any more yet. Still, birds can carry fruit and seeds a long distance.

There is also vinca growing along a back slope heading towards the pond. I have no idea how to control that - ripping it up wouldn't remove the roots and I wouldn't want to use herbicides anywhere near the pond! Vinca's very useful though in the yard to control bad erosion areas so it tends to be beloved down here in Georgia and does have lovely blue flowers very early in spring. Still, I have no desire for it to smother out my native woodland flowers. I have few enough of them as it is!

[rainbowgardener]

Nice post ornery. Thanks for bringing this thread back again. Yes be careful with the vinca. It is one of the invasives in the Meeting woods I was talking about and it absolutely does choke out all the native wildflowers.

[Ornery_Pony]

It was already here when we moved in. It's the pale variegated kind so it doesn't spread as fast as the dark green leafed variety but I'm still considering my options to control it. In my yard I love it, but in my woods is a big no-no! I need to find out if goats like to eat it.

Any suggestions how best I can remove it without using things that might damage the pond would be welcome. We love our singing frogs! It has a thick blackberry patch over much of it so it's not very accessible by hand without dealing with the black berry thicket too. I had considered fencing it off when I have the funds to spare and putting a few goats back there - that's the usual Georgia method to remove things like kudzu and seems to work great if they stay there long enough.

Meanwhile, I dig it up by hand as I am able but it grows faster than I can keep up that back breaking work.