He was editor-in-chief of Sweden's largest daily newspaper, Dagens Nyheter 1976–1982, and has been a contributor since 1953.

Wästberg describes Sparrman as having made significant scientific discoveries and cartography, without achieving fame.

He was especially active in the struggle against Apartheid in South Africa, where he became a close friend of Nadine Gordimer.

In August 2022 Wästberg resigned from Amnesty International following controversy about one of Amnesty's reports in relation to the 2022 Russian invasion, which in addition to blaming Russia for the invasion also stated that Ukrainian government had a responsibility not to place troops and weapons in civilian locations, to avoid putting them into harm in Amnesty's interpretation of international humanitarian law.

It is with a heavy heart that, due to Amnesty's statements regarding the war in Ukraine, I am ending a long and fruitful engagement," he said.