How much would it actually cost to vaccinate the world against COVID-19, wipe out global poverty and reverse climate change? After the UN outlined how it could fight world hunger with just 2% of Elon Musk's fortune, read on as we reveal the likely cost of dealing with the planet's most serious issues, compared to the wealth of the world's richest people. All dollar values in US dollars.

As many as 137 million people in developing countries are at risk of blindness caused by trachoma, an infectious bacterial disease easily treatable with antibiotics but caused by poor sanitation. Of these, 3.6 million need of surgery to prevent them from losing their eyesight. The World Health Organization (WHO) estimates it will cost $1 billion (£730m) to wipe out trachoma by 2030; a new target after it failed to eradicate the disease by its original deadline of 2020.

Beyoncé and Jay-Z are one of America's wealthiest showbiz couples. It's estimated the musicians are worth around $1.4 billion (£1.03bn) between them. While the majority of Beyoncé's wealth comes from world tours and music sales, most of Jay-Z's money comes from his investment portfolio. He is also the world's first hip-hop artist billionaire.

Polio is close to being wiped out, with 99.9% fewer cases now compared to 30 years ago. However, the debilitating disease, which can cause paralysis and limb deformities, is still endemic in three countries: Afghanistan, Nigeria and Pakistan. According to the World Economic Forum (WEF), $1.5 billion (£1.1bn) could obliterate the disease forever. 

Though he could, Michael Jordan won't need to hand over the majority of his fortune, estimated by Forbes to be $1.6 billion (£1.2bn). That's because the world's fourth-richest person got there first. Bill Gates, via his foundation, has already donated $3 billion (£2.2bn) to fund myriad vaccination programmes and is a key player in the Global Polio Eradication Initiative (GPEI), which is working to completely stamp out the disease.

The WHO is committed to preventing all rabies deaths in humans who have contracted the disease from dogs. To eliminate dog-mediated rabies in endemic countries such as India, it will cost around $6.3 billion (£4.6bn), say experts at the Centers for Disease Control and Prevention (CDC) in the US.

Rocked by a series of scandals, the controversial former Uber boss – whose latest venture is thought to be the launch of secretive 'ghost kitchens' – could turn his image around in a big way by donating his $6.3 billion (£4.6bn) fortune to eradicate dog-mediated rabies. But a number of organisations are poised to put up the money instead.

According to a plan published by the UN in November 2021, $6.6 billion (£4.9bn) could save 42 million people around the world from the brink of starvation. Of this, $3.5 billion (£2.6bn) would cover the cost of buying and delivering food, $2 billion (£1.5bn) would be donated in cash and food vouchers, $700 million (£529m) would facilitate the implementation of tailored food programmes, and the remaining $400 million (£302m) would be used to co-ordinate the supply chain. This plan would provide people with one meal a day, the minimum needed to survive. 

The UN created the plan after Elon Musk challenged the organisation's World Food Programme to explain "exactly how" $6.6 billion could combat world hunger. Programme director David Beasley sparked the debate by telling CNN that $6 billion (£4.5bn) could help solve starvation, pointing out that the figure represented just 2% of Musk's staggering fortune. The Tesla and Space X billionaire, and TIME magazine's 2021 Person of the Year, is yet to respond... 

Along with rabies, polio and trachoma, elephantiasis – or lymphatic filariasis – is one of 13 common diseases that are potentially eradicable. At present, 950 million people are at risk of the disease, which causes severe, painful swelling of the joints and other parts of the body and is caused by parasite bites in tropical countries. Although the Global Programme to Eliminate LF announced it was "on track" to eliminate the disease by 2020, this hasn't happened. Experts estimate it would cost $8 billion (£5.87bn) to wipe out elephantiasis through preventive chemotherapy drugs. 

According to Forbes, the former Italian prime minister has a net worth of $8 billion (£5.87bn). His fortune mainly comes from his media group Fininvest but he also has stakes in various banking and publishing firms. Berlusconi shares his wealth with his five children, three of whom have positions at Fininvest. 

Almost half the population of the world is at risk of malaria. While the mosquito-borne disease has been eliminated from many countries, including six more since 2000, it is still prevalent in a number of tropical areas. According to UNICEF, malaria kills more than one million people every year. Researchers at Bentley University in the US believe it would cost at least $8.5 billion (£6.2bn) to wipe out the disease.

The $8.5 billion (£6.2bn) figure is equal to the net worth of Henry Kravis. The American businessman has attracted criticism for his indulgent lifestyle and ruthless buyouts. However, he's also an active supporter of liberal causes. As well as sitting on the board of the Metropolitan Museum of Art (MoMA), Kravis funds an annual $250,000 (£181k) prize for the non-profit sector, launched "Henry Kravis Internships for Teachers of Color", and donated $15 million (£11m) to build a cardiovascular centre in New York. 

According to statistics from the Food Aid Foundation, 821 million people don't have enough to eat. That means one in nine people are malnourished, more than 10% of the world's population. Providing 42 million of these people with one meal a day could cost $6.6 billion (£4.9bn) – but in a world with an abundance of food, researchers at Ceres2030, an organisation set up to support sustainable food systems, believe the cost of ending world hunger completely by 2030 is $330 billion (£242bn), or around $33 billion (£24bn) a year.

Not even the world's richest person could shoulder the estimated $330 billion (£242bn) bill. But plenty could afford to feed the world for a year, including Alain and Gérard Wertheimer, the owners of Chanel. The brothers inherited the French fashion brand from their grandfather Pierre Wertheimer, who launched the company in partnership with Coco Chanel in 1910. Both Alain and Gérard have a net worth of $33 billion (£24bn), according to Forbes. 

Laurence Boone, chief economist at the Organisation for Economic Co-operation and Development (OECD), has revealed that it would cost $50 billion (£37.7bn) to vaccinate the world against COVID-19. According to Our World in Data, just 54.8% of the world's population has received at least one dose of the vaccine. The $50 billion would cover the cost of creating, transporting, and administering the remaining doses.

MacKenzie Scott currently has a fortune of $59 billion (£44.5bn), more than enough to solve the world's vaccine inequality. The novelist and philanthropist received over $30 billion (£22.6bn) as part of her divorce from Amazon founder Jeff Bezos in 2019 and has since donated more than $8.5 billion (£6.4bn) to charity. She's currently the 24th richest person in the world.

According to WaterAid, 2.3 billion people don't have a decent toilet and 844 million people around the world have no access to clean water. Experts at the World Bank estimate it would cost $150 billion (£110bn) a year to provide safe drinking water and sanitation to the entire population of the planet.

Between them, Facebook billionaire Mark Zuckerberg, who has a net worth of $121.2 billion (£91.4bn), and Alibaba co-founder Jack Ma, with a net worth of $36.7 billion (£27.7bn), could comfortably deliver safe drinking water and sanitation to the planet for a year.

In another rough estimate, experts have suggested that it would take around $175 billion (£128.5bn) a year to lift hundreds of millions of people out of extreme poverty, defined as having an income of less than $1.90 (£1.39) a day. 

Four years ago, no single billionaire was worth the $175 billion (£128.5bn) required to rid the world of extreme poverty for a year. Now, the world's three richest people – Elon Musk, Jeff Bezos, and Bernard Arnault – could all afford to cover the bill with change to spare. Bernard Arnault is the chairman and CEO of luxury conglomerate LVMH, which owns brands such as Louis Vuitton, Moet, Dior, and Tiffany & Co. Four of his five children also work for the LVMH empire and, along with Bernard, they boast a combined net worth of $194.8 billion (£147bn). 

Eradicating diseases and providing fresh water and adequate sanitation to the entire population of the world are expensive enough, but tackling climate change comes with an even larger price tag, as the tense negotiations at the recent COP26 summit have shown. The Massachusetts Institute of Technology (MIT) estimates that it would cost a colossal $13 trillion (£9.5tn) to stabilise greenhouse gas levels by 2030.

Data from Capgemini shows there are seven million high-net-worth individuals (HNWIs) in North America – people who have assets (excluding their home) worth $1 million (£734k) or more. The total wealth of all HNWIs in North America is $24.3 trillion (£17.8tn), so between them 53% of these HNWIs could almost cover the $13 trillion (£9.5tn) needed to stabilise greenhouse gas levels by 2030.

​According to the International Energy Agency, "achieving net-zero emissions by 2050 will require nothing short of the complete transformation of the global energy system". This "complete transformation" comes at a staggering cost, with estimates ranging from $44-$150 trillion (£32.3 -£110tn). Among other investments, this money would need to cover the cost of setting up nuclear power plants, switching to biofuels and halting the sale of new internal combustion engine cars. 

The world's 20.8 million HNWIs are worth a total of $79.6 trillion (£58.4tn). If the cost of ditching fossil fuels for good is the most conservative estimate of $44 trillion, around 55% of this wealth could pay for the transformation. The good news is that the money saved by phasing out fossil fuels is likely to cover most if not all of the bill. According to research from Harvard, fossil fuel air pollution causes one in five deaths around the world.

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