The first picture shows the assembled crowd. That's Chapela speaking in the second picture.
Chapela published a disputed paper in Nature asserting that genes from genetically modified crops had flowed into Mexican maize (Nature 414, p. 541-543, 2001), and publically criticized Berkeley's partnership with Syngenta (then Novartis), a Swiss biotech company. A member of the Budget Committee had financial dealings with biotech companies and oversaw the partnership with Syngenta. The Dean of CNR and Chair of ESPM both requested the removal of this member from the committee, but the Chancellor denied that there was any conflict of interest. Shortly thereafter, the Budget Committee decided to deny tenure to Chapela, and the Chancellor upheld the decision.
Today's event consisted of a march to California Hall, following Chapela's last class, to deliver a petition to Chancellor Birgeneau in person. Although the Chancellor received over 200 letters regarding today's event and is present in the building, he chose not to make himself available to hear these concerns or receive the petition.
Update: For more background on Chapela's tenure dispute, see this article. Here is a detailed article on the controversy surrounding the Nature paper. Also, here is a statement by Food First and a response by AgBioView.