ABSTRACT
Scient ific enterpr ises a re organiz ed in term s of multiple concep tual axes, three of whi ch are
impor tant in ecologi cal risk assessment : the first axis compri ses level s of physica l, chemical,
and biologi cal organiz ation; the second, spatial an d temporal scales; and the thir d, dimen-
sions of the analys is. The locat ion of the assessment on these axes determines how it will be
perfor med and what resul ts will be prod uced.
