host: welcome to "global 3000." temples without tourists -- with covid restrictions now lifted, many in cambodia are desperate for visitors to return. the big eat -- insects are being used to fight invasive plants in south africa. and nuclear testing in the u.s. -- radiation victims are fighting for compensation.

nuclear weapons are one of humanity's most lethal inventions. 200,000 people died instantly following the atomic bombs dropped on hiroshima and nagasaki in august 1945. many more lost their lives due to radiation over the following years. the attacks on japan were the first and only use of atomic weapons during a war. the international peace research institute estimates that there are around 13,000 nuclear weapons worldwide. russia owns most of them, then the u.s., and then with considerably fewer, china. despite an overall reduction in nuclear warheads worldwide, the nine nuclear powers are all upgrading their arsenals. while the strategic weapons like those dropped on japan cause devastation and release wide-ranging radiation, tactical devices known as mini-nukes have less explosive

yield but allow for precision bombing, including on battlefields. regardless of the type, all nuclear weapons are deadly, as shown in this report from the u.s. ♪ reporter: grandpa's story, told in newspaper clippings. bill reynolds is collecting them in an album, with his grandson ian and daughter-in-law misty. he been putting it off a long time. now time is pressing. bill has terminal cancer; doctors give him only a few months. >> when i pass on, my kids and grandkids will always have this and know about grandpa. because they don't really understand it now, they are too young to undstand it. like a l of thingsit doesn't mean a lot right now

but maybe sometime it will. reporter: bill is a so-called downwinder, a victim of his own government's nuclear testing in the 1950's and 1960's, back when he was a child. the radioactive fallout traveled for hundreds of miles, even coming down in his idaho town. he was unaware of it until he was first diagnosed with cancer. >> he says, "you were exposed to an atic blast." i said, what you mean? i had never been around anything like that. he said you are a downwinder. that's when i started putting every thing together. my family history. my motr lived e longest of five children and she only lived to be 47.

reporter: bill has been battling cancer for more than ten years now. his retirement savings have long since been depleted, spent on medications and medical bills. now he gets the most expensive drugs for free. he has never received any compensation from the government. >> i am mad as can be at the government. knowingly or unknowingly, the government did it, regardless. reporter: the u.s. government detonated more than 1,000 atomic bombs in the 1950s and 1960s, most of them here in the nevada desert. often the wind blew north, away from las vegas and the metropolises of california, toward sparsely populated areas to the north, and with it, bill's home town in idaho. bill's parents and other adults sometimes even clied the rrounding untains to admire

the mushroom cloud. >> you see right there where the tower is? they would go up there on top of that. they probably would sit and have a beer and watch the colors from the atomic explosion. reporter: bill's hometown is in a valley in gem county. when radiation levels were measuredn the late 1990s, this area was ththird most contamated in the ited states. the fallout at that time settled on fruits, vegetables, and animals. dr. chawla also sees what that did to people. he has been bill's oncologist ever since his first doctor retired. it was only a few years ago that dr. chawla moved to the area. he noticed the many cancer cases immediately.

>> i practiced in chicago five years and i saw maybe two cases of thyroid cancer in five years. i had a very busy practice. here, my first six months i had five thyroid cancers, which i thought was a complete shock. reporter: in bill's case, the cancer is in his bones, blood and prostate, among other ples. the doctor can no longer cure him; he can only give him as much time as possible. a 10-hour drive further south is las vegas. known for its shows and casinos. but also the home of the national atomic test museum. visitors from all over the usa come here to learn about the history of the development of the american atomic bomb. there is also an exhibition dedicated to the hype that surrounded the then new technology in the 1950's. none of the visitors we speak to here are in favor of atomic bombs but some do see their

usefulness. >> if you don't have the capability, the threat of responding, you can be taken over. so yes, it is a weapon that should never be used but you should have because others may use it. >> i understand having them because others have them and fighting back, but i think overall they shouldn't be here because it's not good for anyone. reporter: bill is of the same opinion. he has already lost too many loved ones as a result of the nuclear tests. that's why it scares him when he watches the news these days. it is also why it is so important for him to tell his story until the end. >> i want everybody to know this story. i want everybody to know how dangerous radiation is. with this big conflict in ukraine, and putin being the

way he is, you don't know if he's going to decide to use a nuclear bomb to win his war over there just to say i won the war. reporter: that prospect torments bill. especially when he thinks of his children and grandchildren. the atomic bomb destroyed his life. it should not destroy their lives as well. ♪ host: forests are destroyed for farmland. air, soils and water are polluted and the climate is changing. nature is under pressure. every day, globally, 150 animal and plant species die out. scientists say we may be facing a sixth mass extinction. what can we do to stop it? reporter: who calls this place home? some of its residents we

already know. but many other plants and animals are yet to be discered. humans have only studied a small fraction of the estimated 8 million species that exist. 1 million of them are at risk of extinction. the main reasons are disappearing habitats, pollution, poaching and climate change. species are dying out at a rate and ale never en before. it's dangerous for ecosystems, and therefore for us humans too. but how successful are our attempts to stop this mass loss of life? let's take a look at zoos. some see themselves as conservationists, and many animals that live there are endangered species, or no longer exist in the wild at all. like przewalski's horses. they were bred in captivity and reintroduced to their former home of mongolia. today's wild population of a

few hundred descends from just 12 animals. and yet genetically they are surprisingly diverse. so there's a good chance that this species will survive long term. but these success stories are few and far between. animal conservationists estimate that only 20 species have been saved by zoos. then there are rescue centers. on sumatra in indonesia, there are an estimated 14,000 orangutans left. at the beginning of the last century there were about six times as many. the great apes have disappeared along with rainforests, which have been cleared for palm oil plantations. many baby orangutans have been captured and kept as pets. in the jungle school, they learn to survive in what few protected rainforests there are left. so far nearly 200 animals have been rescued and reintroduced into the wild here.

species can also be protected through regulation. fish numbers are decreasing in our oceans. small boats operating along coastlines report catching far fewer fish. pollution and overfishing are the main reasons. fishing quotas are an attempt to give endangered species time to reproduce. and sustainable methods, such as nets with mesh large enough to spare smaller fish, are intended to protect stocks. around 30 percent of edible fish species are overfished and 60 percent are on the brink. one of the biggest problems here is that conservation agreements are not adequately enforced. and that leads us to the role of protected areas. to date, about 15 percent of the world's land area is protected. this has, among other things, helped to save elephants that

are hunted for ivory and whose populations have been decimated. rangers here are trying to protect them against poachers. other animals are also safer from human intervention in these reserves. but in some reserves, elephants, for example, have reproduced so much that their numbers have actually become a problem. they require more food and space than there is and destroy trees, fields and even villages. one possible solution is to increase the size of such reserves. and in general, to foster intact ecosystems, in which nature regulates itself. perhaps we humans need to learn to see nature not as something to be exploited, but as something that we are part of.

♪ host: what do racoons, sign crayfish and false acacia have in common? they are all invasive species brought over from their original habitats into new ecosystems. either on purpose or by accident, through travel or trade for example. in global ideas we look at the havoc such invasive species can cause. this week we head to south africa, where water hyacinth native to south america has developed into a green plague. but there is a remedy. ♪ reporter: a green mass where open water should be. for decades, the problem at hartebeespoort dam in northern south africa has been growing exponentially. the lake is overgrown with water hyacinth, a plant from

south america, now clogging bodies of water throughout africa. the invasive plant grows extremely fast. the ecological consequences are dramatic. combating the plant has been difficult, despite intense research. >> water hyacintis one of the world's most problematic aquatic weeds. it's been present here since the 1970's and it's a massive problem. they've tried removing it manually and with herbicides but it's still a massive problem as it can cover up to 40% of the dam's surface. reporter: researchers in south africa have been trying to control the invasive plant for years. well-sealed off from the environment, scientists are looking for the water hyacinth's natural enemies. and they've made a big find

that's only four millimeters in size. the inconspicuous water hyacinth grasshopper is also a native of south america. the insects reproduce just as rapidly as the water hyacinths, and the little guys have a big appetite. >> in as much as it's a challenge to rear these planthoppers, we keep a record of every insect we've raised in this facility. in 10 years, we have released over one million insects in this facility. last year, we had over 200,000 across the country. reporter: the procedure is not without its dangers. there are examples worldwide of species used for this purpose becoming pests themselves. lengthy testing procedures are in place to prevent that. >> one of the major concerns we have in biological control is that the insect we release could feed on other plant species. so we mitigate that in this facility by testing these candidate insects on a variety plant species, including native

and crop plants. and we do this testing to make sure the insects we release our what we call host specific. this testing can sometimes take years. it is important because when an excellent -- when an insect is released, we can't edit back. reporter: the tests for the water hyacinth locust are finally complete. the bugs are now being collected and packed for transport. with a leaf of tir favorite food, they're on their way to the hartebeespoort dam. rosali smith of the center for biological control sees to it herself that the animals reach their destination. the denser the water hyacinths grow, the better it is for their little enemy. they can multiply here quickly. >> our approach with releasing the planthoppers is using them

as a green herbicide so as many released as possible, early in the summer, which allows the population to build up quickly. that allows them to damage the plants as soon as possible so they can't expand over the dam. reporter: water hyacinths form dense mats that drift across the lake. when they collide, their underwater roots become entangled, and block out any light. gradually, a huge dense carpet of plants forms. they can completely overgrow bay areas, which is not only an ecological problem, but an economic one too. many people at the dam live from tourism. each year, columns of workers remove the plants from the water with long rakes. it's a slow and laborious process that also only works on smaller waters. in huge areas like this though, the tiny helpers have to step in. the traces of their work can be seen on the water hyacinth's leaves. holes and brown areas testify to the success of the organic pest control.

the nibbled on and dead plants dropped to the ground and slowly decompose underwater. you can also see them from space. within two years, the growth on the dam has decreased from 40 to just five percent. >> this is a site where we have done frequent inundative releases of the planthopper and we know they're here in high numbers because they're jumping around as i pick up this plant. they cause the leaves to become brown. the leaves also recoil on themselves. the plant is heavily damaged and that is what we would like. reporter: in the evening light, the success of the operation can be seen particularly well. swarms of grasshoppers fly over

the water hyacinths. nevertheless, the plant will probably never really disappear. it spreads too quickly. even so, large open water areas have re-emerged on the hartebeespoort dam since their introduction. this promising result could lead to the grasshoppers being used on other infested waters. ♪ host: empty beaches, deserted hotels, abandoned restaurants. for more than two years, global tourism has been knocked sideways. according to the un, the pandemic has put around 120 million jobs in tourism at risk. although ever more borders are reopening, the big comeback has yet to happen and those whose livelihood depends on tourism are becoming increasingly alarmed. reporter: the towers of angkor wat are mysterious and breathtaking.

but they are also nearly deserted. it feels lonely to tour guide son sorm too. before the pandemic, he guided groups of visitors around the landmark almost every morning. and even though tourists are allowed back into cambodia now, son sorm still looks lost in the centuries-old sandstone temples. >> they live to depend on tourism industry that makes income daily from tourism. so when nobody come, and people lose a job. so that is the bad consequences. reporter: tourists currently have a lot of space among the stone figures. son sorm thinks more visitors could be lured back with special deals. but there is one noisy group

right in the middle of cambodia's national monument. tapping and hammering, luis sofor and his team of restorers are working to maintain angkor wat. for the past 25 years, the team has received funding from germany. throughout the pandemic, these so-called temple doctors have continued to clean and seal the masonry. >> at the beginning we also feared that maybe sometime we would lose our jobs. but up to now we stay a little bit in good security of our job that we can go on with the conservation here. we feel very happy with this. reporter: we drive to downtown semrui. everyone here lived from tourism in some way, says son sorm. each year before the pandemic,

around 3 million tourists came. pub street was a party mile full of nightlife; now it's only a shadow of its former self. many shops, bars and hotels have had to shut their doors. >> this one also. this hotel is beautiful as well. so most of the rich people, they come to stay here. >> but nobody is in there? >> nobody in there. >> how many hotels have been closed? this one is closed as well? >> i think it is still closed, yes, still closed. would be more than 300 something hotels still closed. reporter: it's just not worth it yet. meanwhile, the government has invested millions to build

dozens of new asphalt roads. cambodia is clearly setting its hopes on mass tourism. son sorm hopes things pick up soon. this beautiful backdrop is the perfect setting for a wedding video shoot. here in this restaurant, we meet david piot from the local tourism association. he owns a hotel in the city, but prefers not to show it to us in its current dreary state. but does the city really yearn for the days of mass tourism again? >> before you cannot really pick and choose who wants to come. the only thing you can do is manage how they come and how they live together with other markets. yes, of course, mass tourism exists everywhere. it exists in europe, in venice, in paris, in berlin. why should it not exist here? it will exist here regardless of what happens.

reporter: son sorm throws out a fishing net. it might look idyllic, but it's not a relaxing hobby. during the pandemic, many westerners rediscovered their love of nature, but here in cambodia, the 43-year-old has to fish if he wants to eat. >> that is so tough. sometimes i walk from the road where i live because i can't drive mopeds to get close to the pond. i walk 5 kilometers to get to the ponds. sometimes so exhausted, but no choice. because we need to do this for survive. reporter: he bought this house before the pandemic. with his work as a tourist guide and his wife's hotel job, paying off a loan was no problem.

but now he can only find odd jobs. in addition, the prices for petrol and food have risen a lot during the pandemic. these days, dinner is more often than not a disappointment. son sorm has to fight back his tears. >> when come covid, so we don't have the money to pay the loan back to the bank. so that's why we need to save what we can, like eat something like this. reporter: the situation is desperate for son sorm, his wife and many other cambodians. that's why they dream night after night about the tourists coming back. they're needed badly here, the sooner the better. ♪

host: that's all from us at "global 3000" this week. drop us a line with your comments -- global3000@dw.com. and we're on facebook too -- dw global ideas. bye for now. take care.

♪ anchor: this is "dw news." russian advances in eastern ukraine. a second city has fallen this week. moscow bombarding, aiming to circle defensive forces and take control of the industrial heartland. g-7 energy ministers meeting in berlin, making ambitious gls stop