this is "nbc nightly news" with lester holt. good evening we have been under an avalanche of confusing information about covid vaccines and booster shots led by the white house's premature push for those extra shots for everyone to start today. that's not happening today, johnson & johnson did become the latest vaccine maker to claim an extra dose increases effectiveness. in j&j's case, 94% compared to 70% for a single shot. but they still have to submit more data to regulators even friday's endorsement by an fda advisory panel of pfizer booster shots for older americans has still not been formalized, leaving most of the 182 million fully vaccinated americans still waiting for what's hoped to be extra protection from covid. stephanie gosk sorts it out for us. >> reporter: good news today for people who received the single dose johnson & johnson vaccine. the company says new data shows it is holding up against covid-19 variants and j&j says a booster could do even more if given within two months of the first shot, a second dose can provide 94% protection against moderate to severe covid, both pfizer and moderna have said booster of their vaccines will increase antibodies, especially in people over the age of 65. last month the white house said boosters would be widely available in september, but the fda has yet to authorize extra shots for any of the vaccines except for people whose immune systems are compromised. >> my body doesn't make enough antibodies to any disease, i have to be extra careful and extra protected. >> reporter: sarah got her third shot in july for you personally, how much better do you feel having that booster? >> so after every single dose, it is just a little bit of more relief. okay, maybe i am more protected now. >> reporter: last week a fda board recommende pfizer boosters for people over 65 and those considered at high risk. a final decision is expected later this week, but some people aren't waiting. >> many of these are occurring in the context of people who may believe they merited getting a shot ahead of recommendations. >> reporter: federal health officials acknowledged in august that people were gettin unauthorized third shots because they believed they should do we have examples of anyone that got the booster and it harmed them in any way? >> i haven't seen evidence suggesting that it's been harmful to people. i understand for some people, what's the downside i think you want to be sure you're getting the right booster, the right dosing >> reporter: the bottom line, say health experts, is that the vaccines remain strong protection people should wait for final authorization on boosters. >> it does make it really incumbent on the fda and cdc to act quickly so people don't get frustrated and go out and do it on their own. >> stephanie, within days, we could see the pfizer vaccine approved for 65 and older. if that happens and you are sitting here with moderna or j&j shot, where does it leave you? >> lester, you said it this is a decision on the pfizer booster for people that got moderna and johnson & johnson, they're going to have to wait. >> stephanie, thanks very much. there's breaking news in the gabby petito case. the fbi announcing it has identifie remains found in wyoming as hers while the search for her fiance resumed today in florida as suspicion of his involvement grows. miguel almaguer has the latest. >> reporter: gabby petito's body was officially identified today. the coroner now ruling her death a homicide discovered in a remote stretch of wyoming's teton mountain range, authorities haven't said how she died but named her missing fiance, brian laundrie, a person of interest. >> from minute one, brian laundrie has done absolutely nothing other than help himself and bide time to cover his tracks and actions. >> reporter: 2,400 miles away in florida, tonight the intensifying search for laundrie in this alligator infested swampland. laundrie's parents told investigators he came to the 25,000-acr reserve for a hike, a day before he was named a person of interest in his fiance's disappearance. >> terrain is very difficult. essentially 75 of it is underwater. >> reporter: after an fbi raid at the family home laundrie's parents telling nbc news through their attorney he left their house with a backpack and hasn't been seen in a week. >> we have been lucky so far. >> reporter: last spotted together in utah, laundrie and gabby petito were documenting their cross-country trip, her disappearance, his refusal to speak to investigators. >> he was very kind of awkward and confused. >> reporter: resulting in a flood of tips from those who say they saw laundrie alone or the couple's van. >> we came across a white van. >> reporter: with millions following the case, every encounter, including this run-in with police during a domestic dispute, has been analyzed on social media petito's family fears she may have been killed weeks ago this affidavit shows her family received a text from her cell phone in late august which they believe may not have come from her. >> our plan for today is - >> reporter: tonight those with answers to the deepening mystery are gone, and as one search ends, another intensifies. >> miguel joining us now. miguel, do police have much more to go on beyond what laundrie may be able to tell them as potentially the last person to see her alive? >> reporter: lester, there are multiple false sightings of laundrie all been checked by police and cleared. meantime, in wyoming, a final autopsy could reveal exactly when petito was killed and how she died lester >> miguel almaguer, thank you. president biden on the global stage today with his first address to the u.n. general assembly the presiden saying we are at an inflection point and calling for unity while facing sharp criticism from key u.s. allies. peter alexander has more >> reporter: facing growing doubts about his promise to unite america's allies, president biden delivering his debut speech to the united nations, calling for global cooperation to combat climate change and covid. >> bombs and bullets can't defend against covid-19 we need a collective act of science and political will >> reporter: declaring the world is at an inflection point. >> to deliver for our own people, we must also engage deeply with the rest of the world. >> reporter: the speech, a key credibility test for the president who came into office saying he would restore america's relationships that were frayed under former president trump. >> i am sending clear message to the world. america is back. >> reporter: in recent weeks, president biden has been criticized by prominent allies, most notably for america's chaotic troop withdrawal from afghanistan. today, the president trying to turn the page >> we have ended 20 years of conflict in afghanistan, and as we close this period of relentless war, we are opening a new era of relentless diplomacy. >> reporter: that message comes after a stunningly sharp rebuke from france accusing the biden administration of a quote stab in the back france for the first time ever recallin its ambassador after a dispute over the sale of nuclear powered submarines to australia. then the u.s. rivalry with china the president never mentioning the country by name. >> we are not seeking a new cold war the united states is ready to work with any nation that steps up and pursues peaceful resolution to shared challenges >> reporter: topping that list, climate change ahead of a crucial summit this fall, president biden vowing to double american aid to poorer nations tackling the climate crisis. >> whether we choose to fight for our shared future or not, will reverberate for generations to come. >> peter here in new york the president working up on strengthening those alliances tomorrow. what's he got going? >> that's right. at the white house, he is hosting a virtual covid summit, effort to ramp up vaccinations worldwide and increase supply of life-saving medications around the globe. >> peter alexander, thank you. good to have you here. president biden for the first time speaking out about the crisis at the border with new warnings of tens of thousands more haitian migrants on the way to the u.s also the vice president weighing in on those images of border patrol agents on horseback morgan chesky is in texas. >> reporter: tonight on the texas border, 8,500 mostly haitian migrants still inside this tent city questions outnumber answers. who stays, who goes, how much longer can they wait? many beneath the bridge more than a week, surviving on food and water handouts some swimming back to mexico to buy more president biden today addressing the crisis for the first time >> we will get it under control. >> reporter: during a border visit today, texas governor greg abbott blaming the surge on more relaxed border policies. >> when you have an administration that has abandoned any pretense of securing the border and securing our sovereignty, you see the on-rush of people like what we saw walking across this dam. >> reporter: new warnings of more massive groups of haitian migrants possibly on the way to the u.s. internal documents obtained by nbc news show dhs officials tracking 20,000 gathering in colombia, 3,000 in peru, and 1,500 in panama. while the vice president weighing i on images of border patrol agents blocking migrants on horseback. >> human beings should never be treated that way. >> reporter: at a del rio shelter, we met this couple expecting their first child coming here from south america, and spent the last week beneath the del rio bridge. >> i have to feed my baby, got to feed my wife and all my family. >> reporter: planning to become a barber in brooklyn where family lives, hoping he won't be deported. with the biden administration allowing most families applying for asylum to stay in the u.s. until their court dates. >> how is haiti now? >> terrible. >> if you were sent sent back there, what would happen >> probably die. you can be in the street and you receive a gunshot. it is very, very terrible. >> reporter: we learned authorities have already deported about a thousand migrants back to haiti. on one of the flights, sources say a group assaulted three i.c.e. agents and pilots. just the latest sign of rising tension from the border lester >> thank you in 60 seconds, the new warning to airlines about the growing number of unruly, dangerous passengers the faa told airlines they need to do more to stop the staggering number of disruptive passengers on airplanes you've maybe seen some of this behavior yourself tom costello is at reagan national airport. this problem seems to only be getting worse. >> reporter: nearly 4,400 reports so far this year of unruly, dangerous behavior, even air rage behavior, much of it centered around the mask mandate some people upset about having to wear a mask and some times alcohol is involved. passengers and flight attendants assaulted, pilots diverting to other locations. so police can board. now the faa wants the airlines to report back in a week on concrete steps to reduce the bad behavior it is serious business fines up to $35,000, people banned for life by the airline, and the justice department is now under pressure to prosecute cases which have become so serious. lester >> tom costello, thanks. across many parts of the country new covid cases dropped slightly in recent days in the northwest, some hospitals had to make difficult decisions about rationing care as things get worse. gabe gutierrez has more. >> reporter: in spokane, washington, multicare deaconist hospital is turning down more than half of patient transfer requests from other states because there's not enough room. how frustrating is it a year and a half into the pandemic you're still having to deal with this? >> this was a tough week finishing the end of seven days in the icu, i will tell you, it is an emotional roller coaster. >> reporter: as covid cases surge across parts of the northwest, some hospitals are considering whether to activate what's known as crisis standards of care, essentiall guidelines how to ration resources several miles down the freeway is the idaho border, a state with few covid restrictions, no mask mandate, and one of the lowest vaccination rates in the country. >> idaho is known for prideful independence. we have certainly struggled with vaccination rates as we know. and that struggle translated into a hospital system and health care system that's overwhelmed. >> reporter: to relieve the pressure on hospitals, idaho has officially activated crisis standards of care. this vaccine clinic is also being converted into a monoclonal antibody treatment center >> we'll continue as a vaccine clinic and antibody until we get past thi surge and hopefully on the other side of the pandemic. >> reporter: in montana, billings clinic is limiting ecmo treatments. external machines that can function as a critical patient's heart and lungs. we toured the icu earlier this month and met 24-year-old patrick. >> i wouldn't wish this on my worst enemy at all >> reporter: days later he was placed on a ventilator and this weekend passed away, leaves behind a young son. >> every time we moved him, we weren't sure if the end was going to be in that moment i just wanted to be there to hold his hand. >> reporter: at many of these hospitals, the staffing crisis is the worst they've seen in the pandemic. this one in northern idaho alone has 500 job openings lester >> gabe gutierrez, thank you. up next, the impact climate change is having on children. we'll take you to guatemala for a firsthand look ♪ i see trees of green ♪ ♪ red roses too ♪ ♪ i see them bloom for me and you ♪ (music) ♪ so i think to myself ♪ ♪ oh what a wonderful world ♪ the devastation from climate change, leaving families in central america to make the dangerous journey to the u.s. border, hoping to feed their children meagan fitzgerald has more from guatemala in our series "climate challenge. >> reporter: from high above, this looks like a lush landscape when you peel back the layers, a very different story. the fields are ravaged, crops inedible, millions on the brink of starvation are you scared why? [ speaking foreign language ] jose vasquez is struggling to feed his family farmer and father of four says crops are being destroyed with climate change >> what's the problem with this? [ speaking foreign language ] no rain. [ speaking foreign language ] >> reporter: the soil is rapidly deteriorating, triggered by extended periods of drought, followed by torrential rain warming climate causing more catastrophic weather events in 2020, two category four hurricanes hit central america in a span of two weeks, washing out entire villages in guatemala. climatologists war it will only get worse and disproportionally impact impoverished countries. jose took us inside his home where his wife does what she can with the little they have. >> how long will this food last you for? [ speaking foreign language ] two days' worth of food [ speaking foreign language ] so it is a constant hunt for food. nearly half of all children in guatemala under the age of five are chronically malnourished in rural areas, that number soars above 50%. the government is stepping in, providing food for families in need, opening clinics across the country to help starving children these women walked miles to be here so their babies could be monitored. malnutrition severely stunted their growth like this 13-month-old daughter isabella. she lives in this room with her three children, dirt floors, walls made of slats. she says she does the best she can with the little she has but worries that still may not be enough to save her severely malnourished baby girl. >> what do you fear most for your baby [ speaking foreign language ] >> reporter: for millions of guatemalans, this is life boils down to one thing, survival. the climate crisis is fueling the crisis at the u.s. border. hundreds of thousands so desperate, they're making the dangerous trek north like darwin mendez he tried crossing three times. he owes smugglers nearly $30,000 in a country where most people make $6 a day he says he will try again because he can't support his family with his crops, now practically bare [ speaking foreign language ] for so many, it is a choice between starvation and migration. [ speaking foreign language ] a reality as the climate crisis tightens its grip, forcing people to the extremes in guatemala meagan fitzgerald, nbc news. up next for us tonight, the battle to save a towering treasure from a devastating fire finally, the urgent effort to protect a magnificent living piece of history from flames of an inferno. here's erin mclaughlin >> reporter: nestled inside this so-called giant forest, the largest tree in the world and the race to save it from encroaching flames the iconic tree known as general sherman is over 2,000 years old, stands a towering 275 feet high. almost as tall as the statue of liberty. the sequoia attracted tourists from around the world. with flames creeping closer, crews cover the base of its massive trunk with fire resistant wrapping in an effort to try to protect it >> there are so many reasons to protect the tree. for tree lovers, they're so special >> reporter: one massive blaze torching over 23,000 acres. the burn area visible from space. >> we have crews working all through the giant forest looking for those new spot fires and extinguishing them. >> reporter: redwoods like these and giant sequoias have adapte to fire, so even if the flames reach them, they could survive fire officials say it is down to intensity of flames and forest management. concerned visitors sharing fond memories of adventures to see the tree >> sequoia national park is a gem, a national treasure. we have seen real material mortality in the giant sequoia as a result of climate driven fire. >> reporter: the race is on to protect the great general sherman and the surrounding towering treasures erin mclaughlin, nbc every single day, we're all getting a little bit better. we're better cooks... better neighbors... hi. i've got this until you get back. better parents... and better friends. no! no! that's why comcast works around the clock constantly improving america's largest gig-speed broadband network. and just doubled the capacity here. how do things look on your end? -perfect! because we're building a better network every single day. . i'm raj mathai. next on nbc bay area news tonight, dreamforce is back in town. a big party and a big money-maker for san francisco. with star power. multiple locations, but all the stages leading back to the city. >> this is part of the new world we're in and we all know that. >> it comes with major zings the good thing, i feel secure. are we making our fire season even worse? many scientists say yes, and one of them joins us tonight and lets us know if there are better ways to protect our homes. a gut-wrenching day in san jose federal court. a woman testifies about her false result for theranos relating to