>> Laura: THANKS PROFESSOR WOLF FOR JOINING ME TODAY TO TALK ABOUT THE IMPACT OF HEATWAVES ON BIRDS.

>> Wolf: MY PLEASURE.

>> Laura: SO WORLDWIDE HEATWAVES ARE INCREASING IN FREQUENCY AND SEVERITY AND AT THE END OF JULY, PRESIDENT BIDEN ISSUED AN EXECUTIVE ORDER REGARDING EXTREME HEAT, THE RISKS TO HUMANS ARE SERIOUS AND DEADLY WORLDWIDE BUT I WOULD LIKE TO START WITH YOU WITH A TECHNICAL QUESTION.

THERMOREGULATION, HOW DO BIRDS REGULATE THEIR BODY TEMPERATURE VERSUS HOW MAMMALS, HUMANS DO?

>> Wolf: SO, THE GENERAL PROBLEM IS SIMILAR FOR MAMMALS AND BIRDS.

I MEAN, WE HUMANS WHEN THE ENVIRONMENT TEMPERATURE IS COOLER THAN OUR BODY, BELOW 98.6, WE OFF LOAD HEAT PASSIVELY THROUGH RADIATION, CONDUCTION AND CONVECTION.

HEAT JUST GOES FROM HOT TO COLD AND LEAVES OUR BODY.

THAT IS THE INTERNAL HEAT WE PRODUCE IS DISSIPATED IN PART TO THE ENVIRONMENT, RIGHT.

BUT, AS THE TEMPERATURES INCREASE, WE GET A REVERSE ON THE GRADIENT FOR HEAT LOSS, RIGHT.

WHEN THE ENVIRONMENTAL TEMPERATURE GETS HOTTER THAN OUR BODIES, WITH MAMMALS OR BIRDS, WE GET HEAT GAIN FROM THE ENVIRONMENT AND WE ALSO HAVE AN INTERNAL HEAT WE HAVE TO GET RID OF, TO MAINTAIN A STABLE BODY TEMPERATURE.

THIS IS THE GOAL, A PROCESS CALLED HOMEOSTASIS, WHERE WE MAINTAIN A STABLE INTERNAL ENVIRONMENT.

WHEN ENVIRONMENTAL TEMPERATURE IS HOTTER THAN OUR BODY, THE ONLY WAY IT CAN DO THAT IS BY EVAPORATING WATER.

BECAUSE THESE OTHER MEANS OF HEAT TRANSFER, RADIATION, CONDUCTION, CONVECTION, WHICH RELY ON A GRADIENT, THE GRADIENT IS NOW T HOT IS THE OUTSIDE AND OUR BODY COOLER SO WE HAVE HEAT GOING INTO US BY THOSE OTHER MEANS.

SO WE HAVE TO EVAPORATE WATER.

EVAPORATION OF WATER IS VERY EFFECTIVE IN CARRYING OFF HEAT.

IF WE SECRETE WATER ONTO OUR SKIN SURFACE OR WE PANT LIKE A DOG, WE CAN EVAPORATE WATER AND GET RID OF HEAT THAT WAY.

>> Laura: I ACTUALLY SAW A CURVED BILL THRASHER PANTING IN MY FRONT YARD A COUPLE OF SUNDAYS AGO WHEN IT WAS REALLY HOT.

THAT ALARMED ME.

I DON'T TYPICALLY THINK OF BIRDS AS PANTING BUT IS THAT JUST A NORMAL WAY FOR THEM TO REACT?

YEAH, FOR SONG BIRDS LIKE THRASHERS, THAT IS A NORMAL WAY TO GET RID OF HEAT WHEN IT IS HOT.

IF THEY ARE SITTING IN THE SUN, WHERE, RIGHT, THE SUN'S RADIATION HAS A HUGE HEAT LOAD TO AN ANIMAL AND SO THAT IS WHY WE TRY TO AVOID THE SUN WHEN IT IS REALLY HOT, RIGHT, BECAUSE IT IS EQUIVALENT TO ELEVATING THE TEMPERATURE OF A ROOM BY MAYBE 12 TO 20 DEGREES, YOU KNOW, SO THAT THRASHER NOW IS PANTING TO COOL ITSELF.

IT IS EVAPORATING WATER FROM ITS RESPIRATORY SURFACES, PULLING HEAT AWAY FROM THE BODY AND COOLING ITSELF.

THAT IS THE WAY SONG BIRDS COOL, BY PANTING.

THEY DON'T SWEAT LIKE WE DO.

THEY DON'T HAVE SKIN GLANDS WHERE THEY SECRETE WATER ONTO THE SKIN SURFACE AND THE WATER EVAPORATES, RIGHT?

SO, THAT IS WHAT YOUR THRASHER IS DOING.

THE THING IS, THE COST IN TERMS OF WATER IS REALLY HIGH.

YOU LOSE A LOT OF WATER WHEN YOU'RE PANTING LIKE THAT.

THE HOTTER IT IS, THE MORE WATER YOU LOSE BECAUSE YOU HAVE TO COOL MORE.

>> Laura: LAST YEAR YOU AND PHD STUDENT RICK RAMIREZ PUBLISHED A PAPER LOOKING AT HOW SOME SPECIES RESPONDED TO WARMING AT A SITE IN THE MOJAVE DESERT.

WHAT WAS THE DIFFERENCE THAT YOU FOUND BETWEEN HOW BIRD SPECIES AND MAMMAL SPECIES WERE RESPONDING TO HEAT STRESS ON THAT SITE AND IN THAT STUDY?

>> Wolf: SO THAT PAPER WAS PUBLISHED IN SCIENCE WITH ERIC RIDDLE AND STEVE BISSINGER AT BERKELEY AND WE FOUND THAT -- THIS IS A STUDY ON MAMMALS AND BIRDS AND WE COMPARED THE TWO GROUPS.

AND WE FOUND THAT BIRDS, BECAUSE THEY ARE DIURNAL, MEANING THEY ARE ACTIVE DURING THE DAY, THAT THEY ARE DIRECTLY EXPOSED TO THE ENVIRONMENT, RIGHT.

EXTREMES OF THE ENVIRONMENT IN THE MOJAVE DESERT WHERE IT CAN BE 120 OR 130 DEGREES FAHRENHEIT.

AND SO THOSE ANIMALS HAVE TO COPE WITH THAT HEAT DIRECTLY.

YOU KNOW.

THEY ALSO USE BEHAVIORAL MEANS TO AVOID HEAT WHEN THEY CAN, LIKE SEEKING THE SHADE OR THE COOLEST SITE IN THE ENVIRONMENT THEY CAN FIND.

BUT, THEY DON'T OFTEN HAVE OPPORTUNITIES FOR DOING THAT, NOT LIKE SMALL MAMMALS.

MOST SMALL MAMMALS IN THE MOJAVE DESERT ARE NOCTURNAL, NIGHT ACTIVE, SO THEY RETREAT TO BURROWS OR OTHER THERMAL REFUGES DURING THE DAY WHERE THEY AVOID THE MOST SEVERE HEAT STRESS SO THAT REDUCES COSTS IN TERMS OF WATER.

SO, WE FOUND THAT OVER LONG PERIODS OF TIME, THAT THE MAMMALS JUST HAVEN'T BEEN EXPOSED TO THESE EXTREMES SO THEY HAVEN'T EVOLVED ADAPTATIONS TO COPE WITH HEAT STRESS AND SO THEY ARE NOT VERY CAPABLE AS FAR AS COPING WITH HEAT STRESS.

THEY CAN'T -- THEY DON'T SWEAT, THEY ARE NOT GOOD AT PANTING.

AS SOON AS THEY GET HOT THEY MAKE THIS SORT OF EMERGENCY PANIC RESPONSE OF SALIVATING AND WIPING SALIVA ALL OVER THEIR BODIES TO TRY TO GET WATER TO EVAPORATE FROM THEIR SURFACE AND COOL THEM, WHEREAS BIRDS ARE COPING WITH THIS ENVIRONMENT ALL THE TIME AND SO THEY HAVE TO DIRECTLY DEAL WITH IT.

AND THERE SEEMS TO BE A DECLINE IN BIRD COMMUNITIES THAT ARE POTENTIALLY ASSOCIATED WITH THIS WARMING BECAUSE THE INCREASING CHALLENGE OF GETTING RID OF THAT HEAT HAS BIG COSTS IN TERMS OF WATER, RIGHT.

>> Laura: WHETHER THAT PARTICULAR STUDY, I KNOW YOU HAVE ALSO DONE WORK LOOKING AT HEATWAVES IN BIRDS IN AUSTRALIA AND OTHER PLACES.

I KNOW THOSE ARE SITE SPECIFIC BUT I AM CURIOUS WHAT SORT OF BROADER LESSONS YOU'RE LEARNING THAT THE REST OF US CAN ALSO UNDERSTAND, YOU KNOW, HOW THESE RISING TEMPERATURES, HEATWAVES ARE REALLY AFFECTING BIRD POPULATIONS WORLDWIDE.

>> Wolf: HEATWAVES ARE INSTRUCTIVE TO LOOK AT BECAUSE THEY ARE SORT OF THIS 5% OR 1% EVENT THAT IS SUPPOSED TO HAPPEN VERY INFREQUENTLY, RIGHT?

SO, RIGHT NOW OR AT LEAST WITHIN THE LAST DECADE, THE CURRENT HEATWAVE WHERE YOU HAVE THREE TO FIVE DAYS THAT WERE ABOVE THE SORT OF 95TH PERCENTILE FOR HIGH TEMPERATURES, WOULD OCCUR ONCE EVERY 20 YEARS.

THEY ARE PROJECTED IN THE FUTURE TO OCCUR ONCE EVERY ONE OR TWO YEARS AND WE ARE ALREADY SEEING THAT FREQUENCY OF HEATWAVES IS GREATLY INCREASING.

YOU CAN LOOK AROUND THE WORLD RIGHT NOW.

SEATTLE IS SUPPOSED TO BE 110 OR WHATEVER IT WAS SUPPOSED TO BE.

IT WAS OVER 110 DEGREES IN BRITISH COLUMBIA TWO YEARS AGO, RIGHT?

SO, THESE ARE TEMPERATURES THAT ANIMALS HAVE NOT SEEN IN THEIR RECENT EVOLUTIONARY HISTORY SO THEY ARE NOT PREPARED PHYSIOLOGICALLY FOR THEM, RIGHT?

SO, TWO YEARS AGO WE ACTUALLY SAW THE REPORTS OF BABY BIRDS JUMPING OUT NESTS BECAUSE THEY WERE SO HOT.

AND SO, THE HEAT, THESE HEATWAVES HURT BIRDS IN A COUPLE WAYS.

ONE IS THAT THEY MAY JUST CAUSE THEM TO OVERHEAT.

THE BIRD CAN'T EVAPORATE ENOUGH WATER TO STAY SCHOOL SO ITS BODY TEMPERATURE RISES TO AN EXTREME LEVEL WHERE IT JUST DIES, RIGHT?

THAT WOULD BE HEAT STROKE IN HUMANS.

WE SEE THE SAME THING IN HUMANS.

IT IS ONE OF THE CAUSES OF DEATH.

THE OTHER WAY IS THAT THEY COULD EVAPORATE WATER AND COOL THEMSELVES BUT WHEN IT GETS REALLY HOT THEY SUSPEND ACTIVITY AND THEY STOP FORAGING, SO THEY DON'T HAVE ACCESS TO WATER.

SO, THEY MAY JUST RUN THEIR WATER LEVELS DOWN IN THEIR BODY TO AN EXTENT WHERE THEIR BODY DOESN'T FUNCTION ANYMORE.

THEY CAN'T CIRCULATE BLOOD, THEY CAN'T COOL, THEY GET ORGAN SYSTEM FAILURE, THERE IS ALL SORTS OF BAD THINGS THAT HAPPEN.

THOSE ARE SORT OF THE DIRECT WAYS.

DESERTS AND HOT PLACES ARE GOOD PLACES TO LOOK AT THAT BECAUSE WE SEE IT MORE FREQUENTLY AND EXAMPLES ARE MORE STARK, RIGHT.

THE INTERESTING THING IS, OR THE SCARY THING IS, THAT MOST OF THE WARMING, THE POLLS ARE WARMING THREE TO FOUR TIMES FASTER THAN THESE MORE SUBTROPICAL AREAS LIKE DESERTS, RIGHT.

THOSE ANIMALS HAVE NEVER SEEN THESE KIND OF TEMPERATURES IN THEIR RECENT EVOLUTIONARY HISTORY.

SO THEY ARE TOTALLY UNPREPARED FOR THESE HEATWAVES AND I THINK WE ARE SEEING IN THE ARCTIC NOW THAT THIS IS GOING TO BE A REAL PROBLEM, RIGHT.

AND ANIMALS JUST CAN'T COPE WITH THE HEAT, THEY ARE UNPREPARED FOR IT, PHYSIOLOGICALLY OR BEHAVIORALLY.

THERE IS NO PLACE TO ESCAPE.

SO I THINK IN GENERAL, LOOKING AT HOT DESERTS SHOWS US THE STANDARD RESPONSE TO HEAT STRESS AND WHAT THE BEST THAT ANIMALS CAN DO WITH IT, BUT WE EXTEND THAT TO MORE TEMPERATE AREAS WHERE IT IS COOLER AND WE SEE THESE ANIMALS CAN'T COPE WITH THESE EXTREMES HARDLY AT ALL.

THAT WOULD BE ONE THING I WOULD SAY.

>> Laura: JUST WATCHING WHAT HAPPENED IN EUROPE AND THE UNITED KINGDOM IN JULY, YOU KNOW, LONDON, 104-DEGREE TEMPERATURES AND OBVIOUSLY THAT HAS VAST HUMAN IMPACT BUT I COULDN'T HELP BUT THINK OF ALL THE BIRD SPECIES AND OTHER ANIMALS THAT ARE COMPLETELY NOT EQUIPPED TO DEAL WITH THOSE TEMPERATURES.

SO, I THINK THAT MY POINT THERE IS THAT, YOU KNOW, WE KNOW THAT THERE ARE THINGS THAT WE NEED TO DO AS A SOCIETY IN TERMS OF ADDRESSING CLIMATE CHANGE BUT PEOPLE WATCHING THIS PROGRAM, PEOPLE SORT OF WATCHING THESE HEATWAVES AND IMPACTS, WE ALWAYS WONDER WHAT CAN I DO.

ARE THERE ACTIONS THAT YOU CAN TAKE IN YOUR OWN YARD OR NEIGHBORHOOD OR COMMUNITY OR CITY THAT CAN MAKE A DIFFERENCE.

AND I AM CURIOUS, YOU KNOW, WHAT YOU THINK ABOUT THAT.

>> Wolf: FOR URBAN WILDLIFE, I THINK THERE ARE THINGS WE CAN DO AS FAR AS PLANTING TREES.

THEY ARE PAINTING IN PHOENIX, PAINTING THE STREETS A LIGHT GRAY COLOR TO REFLECT HEAT BECAUSE THAT LOWERS SURFACE TEMPERATURE OF THE STREETS BY 10 DEGREES WHICH MEANS THEY ARE ABSORBING MUCH LESS HEAT, RIGHT.

THE ULTIMATE THING IS WE GOT TO MITIGATE AND STOP OUR GREENHOUSE GAS PRODUCTION, REALLY QUICKLY.

BECAUSE, THE RATE AT WHICH THIS IS ACCELERATING IS UNPRECEDENTED.

IF YOU LOOK AT THE AMOUNT OF WATER THAT IS MELTING OFF THE GREENLAND ICE SHEET FROM A RECENT HEATWAVE THERE A WEEK OR TWO AGO, THE CLIMATE SCIENTISTS ARE CONSERVATIVE BY NATURE IN WHAT THEY PUBLISH AND WHAT THEY SAY, BUT IF YOU ASK ANY OF THEM, THINGS ARE HAPPENING MUCH, MUCH MORE RAPIDLY THAN WE COULD HAVE IMAGINED.

AND AS A BIOLOGIST, I LOOK AT THESE DATA AND I DON'T DELVE INTO THEM DEEPLY BUT IF YOU JUST LOOK AT DIFFERENT THINGS, YOU KNOW, ICE SHEETS, TEMPERATURES IN BRITISH COLUMBIA AND ALASKA, NUMBER OF HEATWAVES WE ARE HAVING THAT ARE WIDESPREAD ACROSS EUROPE RIGHT NOW.

IN 2003 OVER 15,000 EXCESS HUMAN DEATHS DURING A HEATWAVE THERE.

SO, HEATWAVES ARE THE BIGGEST KILLER OF HUMANS, BIGGEST ENVIRONMENTAL KILLER OF HUMANS.

IT IS HARD TO FIND OUT WHAT IS GOING ON WITH WILDLIFE BECAUSE IF A BIRD DROPS DEAD IN THE DESERT, WHO IS THERE TO SEE IT?

IT IS LIKE A TREE FALLING IN THE FOREST.

IT IS NOT LIKE PEOPLE ARE OUT THERE SURVEYING THIS ALL THE TIME.

UNLESS IT IS AN EVENT THAT HAPPENS IN AN INHABITED AREA LIKE THE FLYING FOXES IN AUSTRALIA OR BUDGIES IN AUSTRALIA WHERE WE HAVE HAD THESE MASS DIE-OFFS OF THOUSANDS OR 10 THOUSANDS OF OUR ANIMALS, IT IS NOT GENERALLY SEEN.

SO IT IS HARDER TO QUANTIFY WHAT IS GOING ON AND WHERE THESE STRESSORS ARE GOING TO SHOW UP AND HOW MUCH THEY ARE GOING TO HURT ANIMAL POPULATIONS, RIGHT?

SO, THOSE ARE JUST THE DIRECT AFFECTS OF THE CLIMATE EVENTS, RIGHT.

WE ARE DRYING AND ESPECIALLY THE SOUTHWEST, IT IS DRYING.

WE HAVE BEEN UNDER DROUGHT CONDITIONS FOR 20 YEARS.

THAT COULD EXTEND FOR THE FORESEEABLE FUTURE, CERTAINLY MY LIFETIME, FROM THE PROJECTIONS, YOU KNOW, AND IT IS THAT CHRONIC DRYING AND WARMING THAT PUT CHRONIC STRESS ON ANIMALS AND HUMANS, RIGHT?

WE SEE HUMAN POPULATIONS ARE STRESSED BY WATER STRESS.

IF YOU LOOK IN THE WEST, THE COLORADO RIVER, THE WATER STRESS IS JUST GOING TO CONTINUE TO INCREASE.

THAT INCREASE IN TEMPERATURE COMBINED WITH INCREASING DROUGHT, REALLY REDUCES THE ABUNDANCE OF PLANT GROWTH AND SECONDARY PRODUCTIVITY SUCH AS FOOD FOR ANIMALS, INSECTS, THOSE KIND OF THINGS.

SO THAT INCREASES STRESSES ON ALL ANIMAL POPULATIONS AS WELL.

THOSE ARE INDIRECT EFFECTS THAT WE CAN'T REALLY QUANTIFY AT THIS POINT THAT CONTINUE TO ACCELERATE.

>> Laura: THANK YOU DR. WOLF FOR TALKING WITH ME ABOUT THIS TODAY, I APPRECIATE IT.

>> Wolf: SURE, YOU'RE VERY WELCOME AND GREAT SEEING YOU AGAIN.