Japanese Knotweed and the London Plane Tree (Ecosytems)

Planned and Unplanned Introduction of new species in the British Isles, using Japanese Knotweed and the London Plane Tree as examples.This background information could be combined with a local case study if you wished.

Refers to AQA A2 Geog (Ecosystems: Change and Challenge)

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  • Planned and Unplanned introductions of new species (Japanese Knotweed and London Plane Tree)
    • London Plane Tree (PLANNED)
      • Why has it been introduced to cities in the UK?
        • They are large-growing and shade-providing.
        • Resistant to Pollutants
          • The bark flaked off, shedding any pollutants which could interfere with air reaching the trunk.
        • It copes with hot, cold, wet and dry weather, and also poor compacted soil.
        • Widely planted in London in the 18th and 19th Centuries, to line roads and avenues.
        • Aesthetically pleasing (curb appeal for homes in suburbs)
      • Problems?
        • Some killed by fungus brought over from USA. Some trees not disease resistant.
        • Deciduous - Leaves need to be cleared in Autumn or cause slip hazard (not good in claims and compensation culture as could be expensive)
        • There is some evidence that airborne trichomes from the backs of leaves (like spiky hairs) may be causing respiratory symptoms in some people, rather like hay fever.
          • Disputed by some studies, who claim allergy rates are actually lower than for most pollens.
  • Japanese Knotweed (UNPLANNED)
    • Planned and Unplanned introductions of new species (Japanese Knotweed and London Plane Tree)
      • London Plane Tree (PLANNED)
        • Why has it been introduced to cities in the UK?
          • They are large-growing and shade-providing.
          • Resistant to Pollutants
            • The bark flaked off, shedding any pollutants which could interfere with air reaching the trunk.
          • It copes with hot, cold, wet and dry weather, and also poor compacted soil.
          • Widely planted in London in the 18th and 19th Centuries, to line roads and avenues.
          • Aesthetically pleasing (curb appeal for homes in suburbs)
        • Problems?
          • Some killed by fungus brought over from USA. Some trees not disease resistant.
          • Deciduous - Leaves need to be cleared in Autumn or cause slip hazard (not good in claims and compensation culture as could be expensive)
          • There is some evidence that airborne trichomes from the backs of leaves (like spiky hairs) may be causing respiratory symptoms in some people, rather like hay fever.
            • Disputed by some studies, who claim allergy rates are actually lower than for most pollens.
    • Unplanned Introduction of a new species into an area
      • Was originally introduced into urban area deliberately, but has since migrated into unwanted areas, hence becoming invasive.
      • Spreads easily via rhizomes and cut stems or crowns.
      • Under the 1981 Wildlife and Countryside act, it must not be planted or otherwise introduced into the wild.
    • Specific Problems caused the knotweed
      • Damage to Paving and Tarmac
      • Damage to archeologically important sites
      • Reduction in biodiversity by out-shading vegetation.
      • Restricted access to river banks.
      • Damage to flood defence structures.
      • Increased erosion due to exposed bare ground in winter.
      • Unsightly appearance and reduction in land values.
      • Accumulation of litter in established knotweed.
      • Expensive treatment costs of £1 per square metre excluding landscaping.

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