Seeking a 1970s (eller tidigare) roman som inbegriper tidsresor och ekologisk bevarande

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Söker en 1970-talet (eller tidigare) roman som inbegriper tidsresor och ekologisk bevarande. Från beskrivningen som tillhandahålls:

It involved time travel (unexplained) with a girl, from a future so polluted that there weren't any animals but humans any more, traveling back in time to the mid-20th century and meeting her grandfather or great-grandfather or some such who would grow up to be a famous conservationist. She tries to fit in in the new time and fails.

Till sist

she finds her way home, and her ancestor gives her some animals to take with her. I specifically remember wolf cubs. (I did not, at that age, wonder what on earth wolves would eat if the future folks ever tried to establish a wild population again. Now... I do wonder. I wonder about lack of genetic diversity, too.)

Beskrivning

The copy I read didn't have a dust jacket. I'm pretty sure the cover was light, between white and yellow, and the art was in shades of gray and showed the main character and possibly some animals.