What is a weed?
Jack R. Harlan
The species adapted to the new, artificial habitats are mostly crops or weeds. Man generally wants the crops and tries by various means to encourage them; he does not want the weeds and tries by various means to eradicate them. Because both are adapted to the same habitats, however, practices that tend to favor crops also tend to favor weeds. [...]
If we confine the concept of weeds to species adapted to human disturbance, then man is by definition the first and primary weed under whose influence all other weeds have evolved.
Fonte (2° parágrafo, em port.): Crosby, A. W. 1993. Imperialismo ecológico. SP, Companhia das Letras. Excerto de livro originalmente publicado em 1975.

