David Bellamy's credibility at stake?

The Jewish Chronicle reports that:

The British Committee for the Universities of Palestine (Bricup) has urged botanist David Bellamy to pull out of a Zionist Federation event at which he is expected to speak about Israel’s environmental achievements.

Deborah Fink picked up on the JC report and suggested that his appearance at a Zionist Federation event could harm his credibility.

I remember a run-in he had with George Monbiot a few years ago on Channel 4 where Bellamy argued that glaciers are in a general state of growth so I'm wondering, what credibility?