(UNICAMP - 2009 - 2ª fase)
Environment: the case of DDT and the Peregrine
The most reliable evidence of the damaging effect of organochlorine pesticides, such as DDT, on wildlife was demonstrated in 1967 by Dr. D. A. Ratcliffe of the Nature Conservancy in the United Kingdom. The peregrine falcon (Falco peregrinus) was protected in Britain after 1945 and showed a dramatic increase in numbers until, in the mid-1950s, the population went into a sharp decline. This proved to be due to reproductive failure: birds went laying eggs with abnormally thin shells and a large proportion of them were broken during incubation. High concentrations of DDT residues were found in peregrines and in the yolk of their eggs during the mid-1960s. There was no doubt that DDT was the cause of the population decline of these birds , and with the cessation of the use of DDT for agricultural purposes in Britain, peregrine numbers have increased to their formal level.
Adaptado de R. B. Clark, Marine Pollution. Oxford: OUP, p. 142-143.
a) Que problemas começaram a ocorrer no processo de reprodução dos falcões peregrinos, levando ao decréscimo de sua população?
b) Que fatos levaram à conclusão, em meados da década de 60, de que o uso do pesticida DDT estava diretamente relacionado à diminuição do número de falcões peregrinos?
Gabarito:
Resolução:
a) Os falcões começaram a colocar ovos com cascas extremamente finas e uma grande parte deles quebrava durante o processo de incubação.]
b) Os fatos que levaram à conclusão de que esse problema estava relacionado ao DDT foram as altas concentrações da substância encontradas nos falcões peregrinos e nas gemas de seus ovos.