|
As described in Module 2, cascading
effects occur because of the interrelationship among entities
and processes in an ecosystem. As one population, species, process,
or other entity in the ecosystem is altered, other entities are
affected as well.
Primary effects occur when a stressor acts directly on the assessment
endpoint and causes an adverse response; secondary effects occur
when the entity's response becomes a stressor to another entity.
| For example, imagine herbicide applications to a wet meadow
causing the destruction of plants. The loss of these plants
might indirectly affect ducks that feed on them and red-winged
blackbirds that feed among them; these are secondary effects.
|
When cascading effects are of concern, exposure and effects analyses
are conducted iteratively for different ecological entities. They
can become intertwined and difficult to differentiate.
|
Conducting
an Analysis When Cascading Effects Are of Concern