>>> RIGHT NOW ON CBS NEWS BAY AREA, WE GO TO A QUIET CORNER OF YOSEMITE, WHERE A GROUNDBREAKING AND RISKY EXPERIMENT HAS BEEN PLAYING OUT FOR THE PAST 50 YEARS. THAT EVENING. I AM ELIZABETH COOK. >> I AM RYAN YAMAMOTO. IN THE 1970s, A SMALL GROUP OF BERKELEY RESEARCHERS DISCOVERED THAT IF WE DID NOT ALLOW COULD FIRE INTO A FOREST WE WOULD PUT THEM AT RISK FOR THE MEGA FIRES WE SEE TODAY. >> DARREN, WHAT DID YOU FIND? >> BECAUSE OF THAT GOOD FIRE AND BECAUSE OF THE INSPIRATION OF RESEARCHERS AT BERKELEY IN THE 1970s, THIS LITTLE FOREST IN YOSEMITE IS NOW ONE OF THE ONLY EXAMPLES WE HAVE OF WHAT A HEALTHY FOREST IN THE SIERRA IS SUPPOSED TO LOOK LIKE. I WAS INVITED ALONG WITH RESEARCHERS TO SEE IT, AND HERE'S WHAT I SAW. >> YOU HAVE TO REALLY LOVE THE WORK YOU ARE DOING IF JUST GETTING TO THE OFFICE MEANS CARRYING 40 POUNDS ON YOUR BACK. >> I WANT TO KNOW WHAT THE FOREST HAS TO TELL ME. THERE ARE JUST SO MANY SECRETS OUT HERE. SOMEBODY HAS TO TELL THEIR STORY. >> I HAVE BEEN WORKING HERE FOR ALMOST 20 YEARS AND I STILL DON'T REALLY HAVE IT ALL FIGURED OUT AND. >> Reporter: THE STORY THAT BRANDON AND ALEXIS ARE TRYING TO FIGURE OUT AND SHARE WITH THE REST OF US IS WHAT HAPPENS WHEN NATURALLY-OCCURRING LIGHTNING FIRES ARE ALLOWED TO BURN THROUGH THESE FORESTS. >> YOU CAN GO THROUGH THE LAST 50 YEARS OR MORE OF FIRES. >> YOU WILL SEE THAT ONE RIGHT THERE, AND THERE IS PROBABLY ONE THERE OR THERE AND THAT IS ANOTHER ONE, THEN THE REST ARE ALL BURNED DOWN. >> Reporter: SINCE NATURALLY-OCCURRING LIGHTNING FIRES HAVE BEEN ALLOWED TO RETURN TO THE BASIN, THE FLOW IN THE RIVERS HAS INCREASED. THAT IS BECAUSE THERE IS LESS COMPETITION FROM OVERCROWDED FORESTS. MORE WATER IN THE LANDSCAPE MEANS THERE ARE MORE MEADOWS. THEY HAVE DOCUMENTED THAT THE MEADOWS HAVE DECLINED IN SIZE AND NUMBER. MORE MEADOWS MEANS MORE WILDFIRES. MORE WILDFLOWERS MEANS MORE POLLINATORS. THAT IS SOMETHING RESEARCHERS HAVE BEEN THRILLED TO DOCUMENT. ON THIS TRIP, LEX WAS TRYING TO DETERMINE IF THERE IS AN IMPACT ON THE BATS OUT HERE. >> IT DOES A GREAT JOB OF PICKING UP ULTRASONIC SOUNDS. BRENDAN CAN LIST THE CHALLENGES EACH ONE OF THESE FIRES PRESENTED ALMOST LIKE HE IS TALKING ABOUT HIS KIDS. >> 2001, THE HOOVER FIRE. THAT REALLY TESTED THE RESOLVE OF SOME OF THE MANAGERS TO LET THAT ONE BURN. >> Reporter: AS FOR LEX, SHE HAS HER REASONS FOR SPENDING MORE TIME IN THE FIELD HERE THAN MOST RESEARCHERS. >> I AM PROUD OF THE FOREST WE HAVE HERE BUT I ALSO RECOGNIZE THAT WE HAVE A LOT OF WORK TO DO, SO I WANT TO BE ABLE TO BE AN AGENT OF CHANGE. >> Reporter: BOTH WILL TELL YOU THEY ARE ONLY ABLE TO DO THIS WORK BECAUSE OF THE GIANTS AT BERKELEY BEFORE THEM. IN 1970 WHEN THIS PICTURE WAS TAKEN THEY WERE RIDICULED FOR BEING RECKLESS. >> THERE IS MORE RISK THAN REWARD. AT LEAST IF YOU ARE THINKING ABOUT IT FROM A CAREER STANDPOINT. BUT HERE WE ARE BENEFITING FROM THE SCIENCE SIDE OF THAT AND ABLE TO TELL A REALLY NEAT STORY ABOUT FIRE IN THIS NATURAL LANDSCAPE. >> Reporter: ABOUT THOSE 16 MILES, IF ANYBODY WANTS TO SEE HOW SIERRA FORESTS CAN THRIVE OVER THE NEXT 50 YEARS, COME TO THE BASIN WHERE YOU CAN SEE IT FOR YOURSELF TODAY. >> I REALLY LIKE IT HERE. WHEN I THINK OF TEXTBOOK, HEALTHY FIRES, THIS IS WHAT IT LOOKS LIKE TO ME. >> Reporter: BECAUSE THIS IS SUCH A UNIQUE PATCH OF FOREST WE HAVE GOT 50 YEARS OF DOCUMENTATION TO SHOW THE RESULTS. THIS LITTLE KEY SHOWS YOU WHAT THE COMPOSITION OF THE FOREST WAS IN 1969 BEFORE THEY STARTED LETTING THE LIGHTNING FIRES GO. I WILL PLAY THIS FORWARD DECADE BY DECADE. THEY HAVE PUT TOGETHER THIS SERIES OF MAPS SO THAT WE CAN VISUALIZE THE TRANSFORMATION IN THESE FORESTS OVER THE PAST 50 YEARS. WHAT YOU SEE ON THIS ONE IS A COMPLEX OF DIVERSITY. IT IS NOT JUST CONSTANT OVERGROWN YOUNG AND CROWDED PINE TREES. INSTEAD WHAT YOU HAVE ARE A MIX OF MEADOWS AND SHRUB LAND. WHAT FORESTS USED TO BE IN THE SIERRA BEFORE WE STARTED UNKNOWINGLY INKING WE WERE DOING WHAT WAS RIGHT BY REMOVING ALL THE FIRES. NOW AS A CONSEQUENCE, FIRES WILL HAPPEN ONE WAY OR THE OTHER. WHEN FORESTS LOOK LIKE THAT, YOU GET MEGA FIRES. IF THEY LOOK LIKE THIS IT IS A NATURAL DEFENSE THESE FORESTS HAVE EVOLVED FOR THOUSANDS OF YEARS WITHOUT OUR HELP. THAT IS HOW WE HAVE GOTTEN INTO THE PROBLEMS WE HAVE GOTTEN. IT WAS SUCH A UNIQUE EXPERIENCE, GUYS, TO BE ALONG WITH THESE. IT IS A STORY OF YOSEMITE BUT ALSO A STORY ABOUT OUR BACKYARD. THESE ARE RESEARCHERS HERE AT UC BERKELEY IN THE 70s. PEOPLE THOUGHT THEY WERE NUTS! >> SOME STILL DO! >> YEAH, SOME STILL DO, BUT 50 YEARS LATER THEY ARE PROVEN RIGHT. >> THOSE HEALTHY FIRES ARE SO IMPORTANT, BUT WHEN YOU SEE ONE JUST FROM A DISTANCE, YOU CANNOT HELP BUT HOLD YOUR BREATH IF THAT IS GOING TO STAY CONTROLLED, BECAUSE THAT IS THE RISK WITH THESE HEALTHY FIRES. I COULD NOT HELP BUT NOTICE THAT YOU TOOK A LITTLE DRINK FROM THE STREAM THERE. GOOD FOR YOU, NATURE BOY! >> THAT IS ONE THING MOST PEOPLE COMMENT ON BECAUSE THEY KNOW YOU HAVE TO FILTER THE WATER. I AM HOLDING A FILTER IN THE OTHER HAND AND I DID FILTER THAT WATER. >> STILL, THAT HAS TO BE THE CLEANEST WATER YOU HAVE HAD IN A LONG TIME! >> YOU BUT IT WAS! BUT YOU HAVE ALWAYS GOT TO FILTER THE WATER WHEN YOU ARE UP THERE. >> IT WAS A NICE DAY IN THE OFFICE, BUT YOU ACTUALLY HIKED! >> WE ENDED UP GOING OUT EIGHT AND THEN YOU HAVE TO GO BACK OUT THE NEXT DAY. IT WAS TOTALLY WORTH IT. FOR THAT PART OF THE PARK, THE BASIN, IT IS KIND OF JUST EAST OF GLACIER POINT. WHEN YOU GO TO GLACIER POINT, THAT IS ALL
