Chensheng Lu was in his element last month at a speech before a green group at Harvard Law School. The School of Public Health professor was lecturing on his favorite topic–his only subject these days, as it has become his obsession: why he believes bees around the world are in crisis. Lu is convinced, unequivocally, that a popular pesticide hailed by many scientists as a less toxic replacement for farm chemicals proven to be far more dangerous to humans and the environment is actually a killer in its own right. Read more.