Understanding the threat of invasive plants to biodiversity

[Gloria]

Are invasive plants a threat to native biodiversity? It depends on the spatial scale

The authors found some very interesting results. At the local scale invading species always resulted in a loss of native species. However, the outcomes differed at the regional (larger) scale.

When the invader impacted the common species more, diversity at the regional level was unaffected (it was the same in plots with or without invaders).
But when rarer species were disproportionally affected, diversity at the regional level was much lower in invaded than uninvaded plots.

Thus, as the effect of the invader changed from having proportionally greater effects on common to rare species, the potential for extinctions at the regional level increased, as long as there was a large number of rare species in the community.

"The local-scale reduction of diversity by invasives is also the scale at which ecosystem services can be altered by invasive species."

Interestingly, one of the invasive species she and her colleagues have been studying, Amur honeysuckle, has been shown to decrease bird nesting success, decrease survivorship of frog tadpoles in nearby ponds, and increase the risk of tick-borne illness in humans.

"Through local-scale effects, invasive plants can also alter population and meta-population dynamics of native species, which may lead to broad-scale extinctions in the future," Powell concludes.

A synthesis of plant invasion effects on biodiversity across spatial scales

[dapjwy]

Sounds like a couple more good reasons to eradicate the Amur honeysuckle!

[Gloria]

Yes, very good reasons to remove amur from your land. When looked at carefully these types of problems with invasives always occur, what ever else may be going on at a local level. So while species may not be extinct from the state or mountain range, they may be disappearing from a particular stream or woodland lot because of the invasives. How long can this go on without intervention? Sooner or later some species will not have a place to get a foothold and will go extinct. Saying the invasive was not the only cause does nothing to save the species.
And even if those species always exist somewhere else what about this small place left in a condition that does not have healthy ecosystem function?

[dapjwy]

Very well stated, Gloria.

[Cirsium]

Originally Posted by Gloria

Yes, very good reasons to remove amur from your land. When looked at carefully these types of problems with invasives always occur, what ever else may be going on at a local level. So while species may not be extinct from the state or mountain range, they may be disappearing from a particular stream or woodland lot because of the invasives. How long can this go on without intervention? Sooner or later some species will not have a place to get a foothold and will go extinct. Saying the invasive was not the only cause does nothing to save the species.
And even if those species always exist somewhere else what about this small place left in a condition that does not have healthy ecosystem function?

The authors limited the study to extinction, one extreme version of biodiversity degradation. There's a lot of biodiversity degradation by invasive species occurring before it reaches the level of a native species extinction.

It should also be mentioned that invasive plants are only one type of invasive species. If they want to see some major biodiversity degradation (not necessarily limited to extinctions) all they have to look at are invasive species like chestnut blight and Dutch elm disease.

That's not to pick on the authors or their article, they clearly indicated that their study was limited to invasive plant species causing extinctions. But it is a narrow view of how invasive species harm ecosystems.
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[dapjwy]

Originally Posted by Cirsium

The authors limited the study to extinction, one extreme version of biodiversity degradation...

If they want to see some major biodiversity degradation (not necessarily limited to extinctions) all they have to look at are invasive species like chestnut blight and Dutch elm disease.

...But it is a narrow view of how invasive species harm ecosystems.

Great points, Cirsium.

When looked at as a whole and not limited to extremes, it should be clear to anyone truly looking into the situation just how devasting invasives (flora, fauna, pathogens, etc.) really are to natural habitats around the world. How do we get the word out in a clear and concise way to the masses?