Battling a monoculture

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A beautiful view from the coastal cliffs in Exmoor – but not if you look more closely. The right side of the photograph is dominated by a dense yellow-green canopy extending up and down the cliffs for kilometers in each direction. It looks like a scar, or a cancer. What is it?

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If you walk England’s Southwest Coast Path, you’ll pass through this area near the Glenthorne Estate to the west of Porlock Weir. Today it would be difficult walking were it not for the path chainsawed through the landscape. The problem is Rhododendron ponticum (Ericaceae), native to southern Europe and western Asia. It has spread into Britain, where it is enjoying considerable success. Where it grows, it generates a monoculture, outcompeting all other plants with its dense canopy and tangling branches. Where Rhododendron grows there is no understorey. There are no insects, and there are scarcely any birds. Native species can’t eat it. The area feels haunted and sinister.

For Rhododendron, this monoculture is a success story. It has been able to grow better than anything else in the landscape, and now dominates. The only difference between it and the other native species is that it is more successful. Why? Perhaps because it has escaped its natural enemies, growing in a strange land far from home. Or perhaps because its growth has an immediate negative impact on other plants. Or perhaps because it has been helped by people, who first planted it for its showy flowers and ability to provide cover for game animals. There are many ways to achieve a high evolutionary fitness, but in the end some plants are winners and some are losers.

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Just because it has been successful does not mean it is wanted. We humans get to choose the landscapes we want, and the plants of last century have lost their appeal. The European Union has provided funding in partnership with Great Britain to restore this landscape to one dominated by native species. I saw only a small part of the restoration efforts, but it looks like difficult work – pruning and drying and stacking and removing a huge amount of tangled biomass, then returning to the site to plant native trees in their place. I think it will be many years before they succeed – and this story is being repeated all across the country.

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As a comparison, here is a view from a deep Exmoor combe. This landscape is also a patchwork of species resulting from centuries of land use change. But somehow it feels a much more peaceful and functional system than that Rhododendron wasteland.

It would be easier to let the non-natives win – their dominance is in many ways natural – but that is not an outcome many want to see. Certainly I did not want it, walking through that pale imitation of a coastal forest.

3 Comments Add yours

  1. Dante Archangeli says:

    The Oregon Coast has a similar problem with Scotch Broom which I was told was introduced to California as an ornamental plant and also was used to stabilize slopes and sand dunes. It has pretty yellow flowers flowers in the spring and woody dense stalks that quickly form impenetrable thickets with no other plant life.

    1. bblonder says:

      Thanks for your comment, Dante. We humans seem to have poor judgment for our ornamental species.

  2. monomiao says:

    Similar to Kudzu plant here in southeast US….

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