General Impact
Chromolaena odorata forms dense stands preventing establishment of other species, both due to competition and allelopathic effects. When dry, C. odorata becomes a fuel which may promote wild bushfires (PIER 2003). C. odorata may also cause skin complaints and asthma in allergy-prone people. It is a major weed in plantations and croplands, including plantations of rubber, oil palm, forestry and coffee plants.
C. odorata is also a weed of national parks. In the Greater St. Lucia Wetland Park, a recently acclaimed World Heritage Site in South Africa, it is reported to interfere with natural ecosystem processes. Nesting Nile crocodiles (see Crocodylus niloticus in IUCN Red List of Threatened Species) require open, sunny, sandy areas in which to deposit their eggs. C. odorata shades and overtakes nesting sites creating fibrous root mats unsuitable for egg chamber and nest construction. As well as altering this natural habitat, C. odorata produces shade resulting in colder temperatures in any nests that do get constructed, an effect that produces a female-biased sex ratio in the offspring, as well as perhaps preventing embryonic development altogether (Leslie and Spotila 2001).
Location Specific Impacts:Greater St Lucia Wetland Park (South Africa) 
Ecosystem change: Chromolaena odorata is reported to interfere with natural ecosystem processes in the Greater St. Lucia Wetland Park. Nesting Nile crocodiles (see Crocodylus niloticus in IUCN Red List of Threatened Species) require open, sunny, sandy areas in which to deposit their eggs. C. odorata shades and overtakes nesting sites creating fibrous root mats unsuitable for egg chamber and nest construction. As well as altering this natural habitat C. odorata produces shade resulting in colder temperatures in any nests that do get constructed, an effect that produces a female-biased sex ratio in the offspring as well as perhaps preventing embryonic development altogether (Leslie and Spotila 2001).
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