>> CATHY: THERE ARE OVER 400 WILDFIRES BURNING IN CANADA RIGHT NOW AND MORE THAN HALF OF THEM ARE CONSIDERED OUT OF CONTROL.

SMOKE FROM THOSE FIRES HAS BEEN BLOWING ACROSS THE BORDER.

THIS WEEK THE SMOKE DESCENDED ON PARTS OF THE EAST COAST, CREATING A THICK HAZE AND FORCING THE CANCELLATION OF MANY EVENTS.

WE'VE ALREADY HAD AIR QUALITY ALERTS HERE IN MINNESOTA AND MORE COULD BE ON THE WAY.

LEE FRELICH HAS BEEN FOLLOWING THESE FIRES CLOSELY.

HE IS THE DIRECTOR OF THE UNIVERSITY OF MINNESOTA'S CENTER FOR FOREST ECOLOGY.

ALWAYS GOOD TO SEE YOU, PROFESSOR.

WELCOME BACK.

>> NICE TO BE HERE.

>> Cathy: LARGE SWATHS F LAND IN CANADA ARE BURNING RIGHT NOW.

GIVE US A SENSE OF THE SCOPE OF THIS.

>> WELL, THERE ARE OVER 100 FIRES IN QUEBEC, THERE ARE SEVERAL IN NORTHERN ONTARIO, NORTH OF MINNESOTA.

THERE ARE A LOT MORE FIRES IN NORTHERN SASKATCHEWAN, AND ALBERTA, AND BRITISH COLUMBIA, IN FACT, A COUPLE HUNDRED FIRES.

SO, ALL ACROSS THE WHOLE COUNTRY OF CANADA.

USUALLY THE FIRES ARE CONFINED TO ONE PART OF CANADA, JUST WESTERN CANADA OR JUST EASTERN.

AND NOW THEY'RE EVERYWHERE.

>> Eric: WHAT'S CAUSING ALL THIS?

>> WELL, ONE OF THE HOTTEST SPRINGS EVER.

HAS OCCURRED WITH TEMPERATURES 15 AND 20 DEGREES ABOVE NORMAL.

AND IT DRIES TREES OUT AT THIS TIME OF YEAR BECAUSE THE SUN IS SO STRONG, THE DAYS ARE SO LONG, ESPECIALLY UP THERE, IT REALLY JUST BLASTS THE MOISTURE OUT OF THE TREES AND IF YOU HAVE A DROUGHT AND ABOVE-NORMAL TEMPERATURES IN MAY AND EARLY JUNE, IT JUST DRIES THINGS OUT UNBELIEVELY FAST.

>> Cathy: AND THEY'RE LETTING THEM BURN OUT, IS THAT RIGHT, BECAUSE THERE'S JUST TOO MANY OF THEM?

>> WELL, THESE FIRES HAVE SUCH A HIGH INTENSITY THAT THEY CAN'T REALLY BE CONTROLLED.

THE FLAMES ARE -- THAT I'M SEEING ON TV ARE 100, 200, EVEN 300 FEET HIGH.

AND YOU CAN'T EVEN GET WITHIN SEVERAL HUNDRED FEET OF A FLAME LIKE THAT.

THE HEAT IS SO INTENSE.

SO THERE'S BASICALLY NO WAY THEY COULD POSSIBLY BE CONTROLLED, SO WHAT THE FIREFIGHTERS ARE PROBABLY DOING IS HELPING PEOPLE WHO NEED TO EVACUATE AND THINGS LIKE THAT.

AND IF IT RAINS, THEY MIGHT BE ABLE TO JUMP IN AND, YOU KNOW, PUT OUT THE REMNANTS OF A FIRE.

BUT, NO, THESE ARE NCREDIBLY HIGH-INTENSITY FIRES.

MOSTLY IGNITED BY LIGHTNING.

SO A LOT OF DRY LIGHTNING HAS BEEN OCCURRING, AND IT'S JUST A REMARKABLE FIRE SEASON.

THEY'VE ALREADY HAD 15 TIMES AS MUCH AREA BURNED BY FIRE AS YOU WOULD NORMALLY HAVE AT THIS DATE.

>> Cathy: WOW.

>> Eric: IS THE BLOWDOWN FROM THE BOUNDARY WATERS ALL CLEANED UP?

IS THAT FUEL FOR A PROBLEM IN MINNESOTA?

>> IT'S NOT ALL CLEANED UP.

THE HAM LAKE FIRE, THE CAVITY LAKE FIRE BURNED PARTS OF IT.

BUT THERE'S STILL SOME BIG CHUNKS OF IT THAT -- WHERE THE BLOWDOWN FUEL IS STILL IN TACT AND COULD STILL BURN IN A HIGH-INTENSITY FIRE.

>> Eric: WHAT'S YOUR SENSE OF THE POSSIBILITY OF THAT?

>> I THINK IF THERE'S A DROUGHT, WE GET SOME DRY LIGHTNING, I THINK IT'S VERY LIKELY.

AND NOT ONLY THAT, A LOT OF PEOPLE DON'T KNOW THIS, BUT THERE ARE LOTS OF HUGE BLOWDOWN THAT IS ARE HUNDREDS OF THOUSANDS OF ACRES IN SIZE IN CANADA.

THESE BIG DEAR RATIOS THAT HAVE HURRICANE-FORCE WINDS HAVE BEEN OCCURRING FURTHER NORTH THAN THEY USED TO AND THAT'S PROBABLY A CLIMATE CHANGE IMPACT AND THEY'RE UGE SWATHS OF BLOWDOWN FUELS, ESPECIALLY IN ONTARIO AND QUEBEC, AND THEN THERE ARE HUGE AREAS WITH A LOT OF TREES THAT HAVE DIED FROM DROUGHT STRESS OR FROM INSECTS LIKE BARK BEETLES IN WESTERN CANADA.

AND, SO, ALL THAT DRY WOOD, IN ADDITION TO THE LIVE FUELS, YOU KNOW, IS A VERY FLAMMABLE SITUATION.

>> Cathy: SO WE HAVE THIS GOING ON UP THERE.

THE SMOKE IS JUST POURING ACROSS THE BORDER, AS WE MENTIONED IN OUR INTRODUCTION.

AND THE WEATHER'S NOT HELPING, OBVIOUSLY, BECAUSE OF THE JET STREAM.

SO, WILL THIS JUST LAST ALL SUMMER LONG, PERHAPS?

>> IF IT DOESN'T RAIN, IT COULD LAST ALL SUMMER.

AND WHAT TYPICALLY HAPPENS IS A BIG FIRE WILL MAKE A RUN OF 10 OR 15 OR EVEN 20 MILES IN A DAY, AND BURN MAYBE 80 OR 100,000 ACRES OF FOREST, AND IT WILL MAKE AN INCREDIBLE VOLUME OF SMOKE.

AND THE JET STREAM WILL TAKE THAT SOMEWHERE, AND IF IT RUNS INTO A LOW PRESSURE CENTER WITH SOME FRONTS, IT WILL COME DOWN TO THE GROUND AND YOU'LL GET THAT ORANGE LOOK LIKE THEY HAD IN NEW YORK CITY A FEW DAYS AGO.

>> Eric: YEAH.

>> Cathy: SO THESE FIRES, AND, OF COURSE, WE OT CLIMATE CHANGE, OUR FORESTS, I THINK, - HOW WOULD YOU DESCRIBE THE HEALTH F OUR FORESTS?

OBVIOUSLY FIRE IS AN ISSUE, BUT CLIMATE CHANGE HAS ALSO CHANGED THE MAKEUP OF OUR FORESTS.

HOW WORRIED ARE YOU?

>> YEAH, WELL, I'M PRETTY WORRIED THAT MINNESOTA COULD BECOME THE NEW KANSAS, AND THAT THE SOUTHERN-MOST 300 MILES OF THE BORELOE FOREST FROM EDMONTON, ALBERTA, ALL THE WAY TO LAKE SUPERIOR COULD DIE IN THE NEXT SEVERAL DECADES AND BURN AND BECOME GRASSLAND.

THERE'S SOME OTHER BIOME.

AND THAT'S WHY IT'S LISTED AS A TIPPING POINT BY SCIENTISTS.

ONE OF THE WORLD'S TIPPING POINTS.

BECAUSE IF THAT HAPPENS, IT'S A HUGE PULSE OF CARBON INTO THE ATMOSPHERE.

>> Eric: WE'RE GOING TO HAVE YOU BACK WHEN YOU CAN SHARE SOME GOOD NEWS WITH US.

>> Cathy: ALTHOUGH IT MAY