The risks of alien plant invasions to land owners in the Garden Route

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Presentation by Christo Fabricius to the South Cape Land Owners Iniative

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The risks of alien plant invasions to land owners in the Garden Route

  1. 1. Risks of alien plant infestations to land owners Christo Fabricius
  2. 2. National Invasive Alien Plant Survey Initial clearing = 48 years/R52 billion 1. 2. 3. 4. 5. Acacia mearnsii, A. dealbata & A. decurrens Eucalyptus spp. Pinus spp. Opuntia spp. Salix spp. Economic impact = R13 billion/annum 8% 51% 5% 39% 20% 8% 22% 1% 16% 9% (Kotze et al., 2010) 20%
  3. 3. Pines invading the watersheds of the Western Cape
  4. 4. If we do not clear invasive alien plants …
  5. 5. Nitrogen Fuel load Soil loss levels after fire Stream flow Infested Not infested Infested Crop yields Carrying capacity Not infested
  6. 6. Negative impacts on agriculture • More evaporation – Reduced stream flow – Less water = higher concentrations of polluting nutrients • • • • Reduced ground water quantity, quality More intense fires Increased soil erosion Serious water quality and quantity problems
  7. 7. YIELD per Hectare Profitable Unprofitable COSTS (Chemicals; fuel; labour; ALIEN PLANT MANAGEMENT)
  8. 8. 4. Biological Control For many invading species, in many parts of the world, it is the only hope. Melanterius weevil on Acacia cyclops Species Red sesbania Benefit :cost ratio 45 : 1 Lantana Long-leaved wattle 34 : 1 1 465 : 1 Golden wattle 4 333 : 1 Silky hakea 611 : 1

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