Poignant, at this time year. Londons city hall has decided to open its doors for a festive celebration, for some of those sleeping rough an initiative backed by the mayor and charities in the capital. A recent report found that london is the worst place in the country for homelessness. Alpa patel reports. Smoked salmon or ham . The mayor of london, serving food to just some of the 100 homeless people, invited for christmas lunch. Its the first time an event like this has been held in city hall. As well as food, people are offered haircuts and eye check ups, too. Claire became homeless when she wasjust 13. She spent the next 30 years either on the streets, or in prison. Id be a lot more careful. I mean if you know people that is fair enough but you have to be very careful where you sleep. Be careful, you cant leave your stuff any more. Its got a lot harder as well, especially with everything going on. With help, claire now has a place of her own. She is hopeful this event will forge partnerships and improve homelessness. But she is not convinced there is enough of a joined up approach. Im still waiting for support with mental health. But again that depends on where you live, what borough youre in, what area youre in, so it can all depend on a lot of different things. Honest . I dont think its very fair. According to the charity, shelter, 170,000 people are sleeping rough, or in temporary accommodation, in london. A rise of 2,000 people on last year. The mayor of london says he is aware the picture is bleak. Its unacceptable that in one of the richest cities in the world we have got parts of london which had fantastic michelin star restaurants but also more than half a dozen food banks. We are doing our bit to deal with the symptoms as i said, helping a record numbers of londoners. And tackling the complicated causes of homelessness is what many of those who attended this event are longing to see. Coming up at 6am breakfast with Naga Munchetty but first the bbcs science editor David Shukman reports on the battle for the future of the Worlds Largest ra i nforest in amazon under threat. The amazon rainforest is the largest in the world, home to an incredible variety of life. But suddenly, it is all at risk. The clearing of the trees is accelerating, and scientists are warning about the danger of irreversible loss. Its never going to come back again. We are never going to be able to build an amazon. Its going to be gone forever. Brazil has a new president , and he wants to develop the amazon, and he is encouraging his supporters to exploit it. So the people who live inside the forest fear that their days may be numbered. A gentle view of the field and forest in the amazon, but this region is now the scene of a struggle over land and a battle for survival. This is the home of uru eu wau wau, a tiny band ofjust 120. They are one of many indigenous groups that have lived in the rainforest for centuries. The uru eu wau wau are meant to be protected in special reserves, but they feel the new government of brazil is against them. One of the elders of the group describes the rituals of getting ready for war. A crucial task is preparing weapons. The wood for the arrows comes from particular trees, the feathers from special birds. He has dark memories of the first contacts with the outside world. In the middle of the last century, settlers and loggers advanced into the forest and fought the Indigenous People for territory. His wife, boreha, was wounded as a young girl. An attack left her with scars and killed her family. Theres been a long and violent history here, and boreha says she is now worried once more. Here, they are making an ink to use as a war paint. A fruit is grated to get at thejuice, a process given special meaning now, as the risks of an attack seem to grow. The pulp is squeezed and the liquid is mixed with charcoal. Everything they hear from the president about their way of life sounds hostile. Adorning themselves with the paint is more than just tradition. Its because of a real sense of needing to be on guard. So they patrol what is meant to be their protected area. But they discover incursions. This track was carved out to steal timber or create new farmland. Miners often break in, as well. Sights like this are painful, because this is home, where they gather food and hunt. Previous governments saw Indigenous People as guardians of the amazon. But now, their whole future is uncertain. The youngest generation may not grow up amid these trees, given the negative attitude of the new president , jair bolsonaro. We use our drone to get a view of the dark green edge of the reserve. Farmland presses right up against it, and president bolsonaro says farmers should be allowed inside. In his view, Indigenous People have too much land. His election heralded a right wing agenda, in favour of agriculture and of guns. He thrills his supporters with talk of opening up the amazon. Since he came to office, bullets were fired at the sign marking the land of the uru eu wau wau. Tensions are escalating. Up the road, we get talking to some localfarmers, and they say exactly the kind of things the president says that the system of forest reserves for Indigenous People is wrong, and that farmers need more land. With the president on their side, farmers and loggers feel a new freedom to clear trees. We found this vast area of bare earth and dead trunks. Huge tracts of forest are being wiped out. My footsteps and distant birdsong are the only sounds. It is tragic to see this close up. To bring these trees down to the ground, theyjust knock them over with a bulldozer. This is happening all over the amazon to create new farmland, and the result is that the great forest has never been under such pressure. Many trees have already made way for agriculture, nearly 18 of the forest, and the president is now pushing for much more aggressive development. We are guided to this tiny clearing to see where illegal loggers were at work. This kind of wood fetches a high price on the black market. Stealing rare timber is nothing new here in the amazon, but under the new government, its never been so easy. The agencies meant to stop this kind of thing from happening are incredibly overstretched, and the president wants to weaken the Legal Protections for the forest. To make the timber less valuable, environment officials cut into the logs so they cant be turned into planks. But they cant talk about their work, because theyve been banned from speaking to the media. So yourjob, protecting the forests, must be very difficult, is it . You are trying to save the forest. So we have to meet this official in secret, his face hidden and voice changed. He says the government is trying to cover up the loss of the forest. And the scale of the deforestation he describes is so vast that it is hard to visualise. Up here, at the top of this 50 metre high observation tower, the view is just phenomenal, out over what looks like a great ocean of green. This is the canopy of the largest rainforest in the world. The problem is that more and more of it is being chopped down. It is hard to believe, but an area the size of a football pitch is being cleared every single minute. What that means is that forest that would cover more than 2,000 pitches is just vanishing every day, and the signs are that this rate of devastation could accelerate. The biggest single reason the forests are cleared is to create pasture for cattle. They are grazing on land that used to be forest. Brazilian beef is in big demand all over the world, and the president s vision for boosting exports has delighted farmers like vanderley wegner, who says other countries cut their forests down long ago. During our time in the amazon, we keep hearing that only brazil can decide what to do with the forest. But the trees store so much carbon that the more of them are cut down, the more we lose one of the very few Things Holding up a rise in global temperatures, so what happens here matters far beyond brazil. The more we lose one of the very few Things Holding back to rise in global temperatures, so what happens here matters far beyond brazil. So my name is erika berenguer. I am a scientist, even though i dont wear a white coat. So i work in the amazon, this beautiful forest, and i am from brazil. Erika is a researcher based at the university of oxford. She has studied the trees of the amazon for the past ten years and she has always loved them. For me, it is really important because the amazon cannot speak up, the trees cant speak up, they cannot say that they are worth it, and they have a value, they are really important. So i have made it as my life, i have made it to study them, understand them, understand the forest and be able to speak up about its importance. Erika has got to know the forest very well. And she guides me through a stretch of it that is constantly under assault from loggers and invaders. So you have become used to seeing a thriving forest. Yeah. Whats it like when you see the opposite the forest cleared . It is very sad. Its very, very sad. Because emotionally, i know everything i am losing, the connection is not there anymore, the life, but also i know how much biodiversity we are losing, how much it is contributing to climate change, so both rationally and emotionally, its really difficult. Here is one of the biggest trees in this stretch of forest. I mean, that isjust immense, isnt it . Yeah it is a really beautiful brazil nut. And you can see that far it stands above everybody else. How tall would you reckon that is . Oh, it is about a0 metres, this one. Yeah, i would say 120 feet. That is a long way up. Laughs. Yeah, it is so it probably took centuries to get to this size and also that tall. They fight for the sun. They love the sun. Yeah. The challenge for scientists is to get accurate measurement the challenge for scientists is to get accurate measurements of the forest. And this is one way to do that. Speaks in native language. Erika waits down on the ground. Shes asking for samples of wood. Her assistant, way up above, cuts away a few branches and throws them down. 0ops. What she is trying to find out is the flow of carbon in the forest. So when we are in the forest like this and want to know how much carbon is stored, you have to measure the diameter of all trees, so you know its size. So this one for example is. 15. 6 centimetres, and once we do it. We paint the tree. She has followed the growth of the same batch of trees year after year to assess the role they play in the climate. They are helping us for free, to remove carbon from the atmosphere, and put it in the forest and lock it up in here. Its the sheer size of the forest that makes it significant. We have used graphics to show how the countless leaves absorb Carbon Dioxide. Thats the gas heating up the planet. As human activity keeps adding more and more Carbon Dioxide to the air, Magnificent Trees like this pull a lot of it in. But chop it down and burn it, and all the carbon that has been stored inside over the many years is suddenly released back to the atmosphere. Which, of course, increases the speed of global warming. So erikas research is all the more urgent. In this lab, she studies the wood collected from the forest to work out how much carbon the amazon holds. So in these bags here, we have lots of little bits of wood that come from different forests, and what we do is that we collect the wood from the forest, put them in these big oven dryers behind me to remove the moisture, so they become super dry, so we pop them on the stale, half of the weight here on the scale is actually carbon. And this is really important to help us understand how much carbon the amazon is removing from the air, from the atmosphere and locking up in vegetation. So we can understand the importance of the amazon to fight climate change. And the latest science is revealing about the amazons store of carbon. It is the equivalent of america burning fossil fuels for nearly a century. 97 years of the us fossil fuel emissions, that is how much carbon there is in this place. Because a big tree might store three tons of carbon, four tons of carbon its a lot of carbon. The rich greens of the forest have another vital role as well. They form the most vibrant habitat on earth. Home to an extraordinary tenth of all species in the natural world. Some of them unnerving, others adorable. They are so wonderful. Its so full of life, its so full. Just so beautiful, and to lose it. Its never going to come back again. Were never going to be able to build an amazon. Its going to be gone forever. So once it is gone, its just gone, we cant rebuild it. Its not a building. Field by field, this whole region is being transformed. And its triggered a barrage of International Criticism of brazil. Our Research Shows how easily and rapidly trees can be wiped out. And the brazilian government is now saying to the outside world pay us to keep the forest. In the meantime, the onslaught on the trees continues. And it can be dangerous asking awkward questions. As i hearfrom thisjournalist and charity worker, gabriel 0shida, as we travel through land that was forest. The landscape were driving through looks very charming, with small fields, a very rattly road, obviously, but a few cows, a few trees, but what is actually going on here behind the scenes . What is it really like . Even though it looks quiet and peaceful, this area is quite dangerous. This is like a wild west movie. So people are around carrying weapons and people are doing whatever they want. They can invade New Territories i myself have already been threatened here. Actually, i have received Death Threats in this region, made by illegal loggers. What effect has there been from the election of president bolsonaro . After bolsonaro got elected, we can clearly see that these guys here these invaders, these land grabbers they feel much more confident about what they are doing. And they feel that now they have the law on their side, and now they have they can do whatever because our presidency will support them. So Indigenous People in the forest, like the uru eu wau wau, now face a lot more pressure. So this is the forest of the uru eu wau wau . I show them the view from space of what they are experiencing every day on the ground. With all this farmland all around you, and you are about there, just in that little corner. So you have got farms, right deforested land, right next to you. And while we are with them, we hear a very depressing fact. That the uru eu wau wau have had such a troubled experience with the outside world, that to describe white people and invaders, they have just a single word. tapuya means invader, but also white people. Because that was the only thing that they knew. So they didnt know there were white people who could be friends with them. Because in the past, they were always having battles and conflicts against white people. So nowadays, they only have this word, one single word for white people and invaders, which is tapuya. Sings. The fate of these people hangs in the balance. The children here are learning traditional skills, and they have rights under brazilian law. But they are outnumbered and powerful forces are circling outside. Hello there. Well, it doesnt look like theres going to be any snowfall on Christmas Day, but because itll be quite cold, there could be a little bit of festive frost to start the day. And the reason for the settled cold weather for Christmas Day is this ridge of High Pressure, which will settle things down, bring light winds and plenty of sunshine. But it is short lived because this next area of low pressure will come sweeping in for boxing day to bring us all a spell of wet and windy weather. Youll also notice as the wet and windy weather arrives, itll push the Christmas Day blue cold air away from our shores and it will be replaced by the oranges and yellows, indicating very mild conditions, particularly as we end the week and head on into the weekend. But as we start Christmas Day, very early on, therell be one or two showers around, but even these will fade. As that ridge of High Pressure builds in, theyll settle down, with clearing skies for many and with lighter winds, its going to turn quite cold. Temperatures close to freezing in many places, with a touch of frost in places, maybe a little bit of mist and fog too. So Christmas Day is looking cold, but dry, bright, plenty of sunshine, and, yes, well have a little bit of festive frost to start the day in places. So a dry, sunny day for most, a little bit of patchy cloud for north west england, perhaps northern and western scotland where there could be the odd shower, but even these will be fading through the day. Sunshine will be fading across the far west, though. Later in the day, high cloud starts to move in ahead of that weather system. But most places will see the sunshine continue, but its going to be a chillier day, particularly in the south, we have been used to temperatures in single figure for most. And as the temperatures fall away later in the day, it looks like fog could become a problem across central, northern and eastern england, so bear that in mind if you are heading out on the roads. It wont last long, we think, though, because as the winds start to pick up ahead of this weather system, then the fog will tend to lift. It will turn much wetter and windy by the end of the night across western areas. Those temperatures also rising. But again, its going to be quite a chilly one across the north and the east of the uk. So a very different feel to the weather for boxing day. Were back to the unsettled theme, this area of low pressure bringing rain and strong winds, northern ireland, wales, south west england, then pushing northwards and eastwards across the country through the day. Could start quite chilly but dry across the north and the east, but the rain and the wind will arrive here. And, yes, the white there, we could see some transient snow over the Higher Ground of Northern England and into the scottish mountains. Those temperatures climbing to double figures in the south. But still quite chilly in the north and the east. But as we head through the week to friday and indeed the weekend, its set to turn much milder thanks