Bill Leikam was reviewing footage from a wildlife camera he placed along a Palo Alto creekbed recently when something unfamiliar scampered across the screen. … Eventually, he recognized the mysterious creature as a critically important species that has long been missing from his beloved Baylands — a mammal that California wildlife officials have hailed as a “climate hero.” … For decades, developers, municipalities and farmers focused on beavers as a problem that required mitigation or removal. Now, the species known as Castor canadensis is seen as offering myriad benefits: It can help to mitigate drought and wildfires through natural water management; it is considered a keystone species for its ability to foster biodiversity; and it can restore habitat through its ecosystem engineering.