For the past two years, crop failure in Africa has led to devastating food shortages; across the continent, nearly 50 million people now need emergency aid. Seven countries have declared a state of disaster, and Ethiopia is facing its worst drought in 50 years. Meanwhile, southern Africa is having one of its driest seasons in more than 35 years.

The immediate cause of the world’s biggest food crisis in many years has been El Niño, the natural phenomenon that occurs every few years, disrupting weather patterns across the world. What began in 2014 and continued through this year has led to record temperatures and widespread droughts followed by floods. The human fallout has been extreme malnutrition and disease.

But this food crisis cannot be attributed entirely to natural causes. Many African and western countries have encouraged farmers to grow and eat a single staple crop, maize, which is not suited to drought or to warmer temperatures.

The food crisis is expected to peak over the next two months, but governments around the world have pledged only half the money needed to feed everyone. While few people are expected to die of starvation, millions of children will be malnourished, and this will adversely affect their education and long-term health.

Last month, I visited three of the countries on the frontline of the crisis – Malawi, Zimbabwe and Zambia – to share maize and other meals with their farmers, humanitarians, villagers, politicians and traders. This is what they told me.

Elvas Munthali, a Malawian aid worker, with her meal of nsima [made from maize flour and water], chicken, beans and spinach. She works for Concern Worldwide. We ate at a restaurant in Njale, near the border with Mozambique.

I cover villages in the very south of Malawi. I am shocked at what I am seeing. When I visit people, they say, “We have no seeds, no food.” But we cannot reach everyone. I went to one house this week where the woman’s husband had died and she had four children to feed. She hadn’t eaten all day. She had HIV and no strength, but because she had to find food, she had to work in the fields.

I am very proud to be an aid worker in my own country. People tell me about their lives, and I feel I am helping. I sit down and eat what they are eating. For me, it is a small thing, but for them, it is something big.

People don’t have a nutritious diet; they find it hard to get hold of meat and oils. It is expensive to eat properly. The climate is changing: now, we plant maize at the end of December or even January; we used to do that in November.

Like most people in Malawi, I know what it is to go hungry. My family depended on farming; in the hungry season, we would take tea and have very little to eat. I am supporting my brother through school now, because my parents have no money.

I like my nsima. I eat it every day, even Christmas Day – I far prefer the taste and texture to anything else.

Alufufasi Yalu lives in Nkhundi, southern Malawi. We meet at a house she has been lent by a family in the village. She has no food.

There are five of us in my household. I have only one child who is four years old, but my sister is here with her two children. Other people in the village receive food aid, but I have to beg because I was missed off the list when they were taking names. I was asleep at the time. I sleep a lot because I have HIV. The drugs, which I take every night, make me extra weak and hungry.

My child is also very weak. We have had some water today, but I don’t know what we will eat. Someone might give us a sweet potato. There are mangoes in the trees, but someone needs to go up there for them, and I can’t.

I’ve been told I cannot be put on to a feeding programme until March, and I don’t think I will live that long. Sometimes a neighbour gives me porridge. The children depend on a school feeding programme; they help each other.

Nelson Mudzingwa is a small farmer in central Zimbabwe. We meet for lunch in a suburb of Harare.

I am one of the 400,000 people who benefited from Robert Mugabe’s land reform. The land I farm, eight hectares [19.76 acres] near Masvingo, is about 300km from Harare; it used to be part of a 15,000-hectare estate occupied by just three British farmers. They were good, but they exported all their crops to Europe. There are now 500 families here, growing food for Zimbabweans.

It is good land. I grow maize, sorghum, cow peas, fruit and millet, and raise livestock. This year we got a little rain in February, but had our worst drought in years and I lost some cattle. Still, my family never went short of food. Most of what we eat comes from the farm.

We practise agro-ecological farming and are part of a farmers’ group called Zimsoff. We host the secretariat of La Via Campesina, the global peasants’ movement, which has 300 million members around the world. On the farm, we collect every drop of water; we have dug canals and made dams from earth. We look after the soil to prevent erosion, and we store the seed. We feed the soil with organic manure, not with poisons.

When we came here in 2000, we had no infrastructure, and we had to build our houses. We have learned to focus on growing small grains such as sorghum and millet rather than maize, because we cannot be sure of the changing climate. What we have learned is that if you go for monocultures, you are vulnerable to disaster. Diversity is a weapon to protect farmers and provide food.

Zimbabwe has declared a food disaster and appealed for $1.5bn (£1.2bn) to feed 4 million people. With good ecological practice, this could have been mostly averted. The areas that diversified the most this year have survived the best. But the government is still obsessed with the conventional agriculture model, and is influenced by the seed breeders and big chemical companies; they concentrate on maize and tobacco and hybrid seeds.

The hunger in southern Africa this year goes back to the “green revolution” of the 1960s, when everyone was encouraged to grow food with chemicals. It wasn’t green at all. Maize became the only crop in southern Africa. But if you go deep into rural areas, you find people eating different foods.

What are the lessons of this drought? That we must avoid food miles, chemicals, genetically modified crops. Is it possible for our kind of agro-ecological farming to feed all of Zimbabwe? Yes. And the message is getting through.

Farmer Lucia Bello lives in the village of Aloufasi in Malawi; she is pictured above with some of her children and her sister’s orphans. She received food aid for the first time in November.

I am the head of a household of nine. I lost my husband 10 years ago and I have eight children to feed, including four orphans, my eldest sister’s children. I depend on farming, but there was a total crop failure this year.

I was given a 50kg sack of sorghum in November, enough for two and a half weeks; it was supposed to last a month. We eat just one meal a day. Last month I was so hungry, I had no option but to eat water lilies. I walked about six hours to the Mozambique border to find them. Ugh – they are really bitter. Children who cannot eat do not go to school. I’ve thought of putting salt in hot water, but they won’t drink it.

What is it like to be hungry? Your sight is affected. Your heart runs fast. Your stomach hurts, your head hurts. You are confused and it consumes you. When the food came, it was such a relief. Without it, we would all have died.

I have prepared my land to grow maize. It is all ready for the rains, but I have no seeds. Even if I can plant in December, it will be April before we have any food. Until then, we will need help.

Coco Ushiyama heads the World Food Programme in Malawi. We have lunch at her offices in Lilongwe.

The numbers who need food are rising fast. In November, 5.7 million Malawians needed food; in December, it has reached 6.2 million. By January, we will have 6.5 million hungry people, almost one in three people in this country, and it will last at least until March.

We are all on overdrive. I sleep at night, but there is just so much to do. We plan for the worst and hope for the best. We should have enough maize, but we do not have enough pulses, or vegetable oil, or vitamins and nutritious foods.

We are contracting ships; government money is being reallocated from other budgets. Meanwhile, there is talk of speculation, of traders waiting to make a killing. The prices might be stabilising, but they are still abnormally high. We are appealing for 15 more trucks and three helicopters; hopefully, we won’t need them.

Malawi has been very unlucky. Last year, we had massive floods; this year, it has been drought. Now the rains are coming and the roads will be damaged, which makes it harder to distribute food.

Is there enough money for this crisis? No – there are too many fires around the world that need extinguishing. The seven worst-hit countries in Africa are appealing for $2.9bn, but it’s not all there yet. The Chinese have sent 6,500 tonnes of rice; the US has given cash and food; more food has come from Zambia and Mexico.

This crisis is not about food production. Two years ago, Malawi was having bumper harvests, yet we were still doing handouts. You can have a surplus and still have pockets of hunger. It’s the same around the world. Of Malawi’s population of 17 million, 9 million are poor and have to spend 50%-70% of their income on food. Crop diversification is needed, but it takes time.

Carrington Mwanda buys and sells maize. We met him in his storeroom in Nsanje market, Malawi.

I sell 50kg sacks of maize for 14,000 kwacha (£15.50). The price has gone up a lot and I make a profit, but not much. Lots of other big buyers have stored food and they are waiting to sell but I don’t think the price will go much higher.

I have about 600 sacks. I bought them last month for 10,000 kwacha. Lots of people cannot afford to buy it but that is how the market works. If a hungry woman or a disabled person came to me and asked for food, I would give them one or two kilogrammes.

Food shortage like this is business for me. It is unpredictable. It’s 50:50 whether we make a profit. We can’t afford to let stock run out, so when we are down to 50 bags we will buy more.

David Gordon is one of Zambia’s biggest farmers. We meet for lunch on his estate, 40km from Lusaka.

I used to feed Zambia: I was the biggest maize grower in the country. We grew about 2,000 hectares of maize and yields were good. We could produce up to 16,000 tonnes a year. I own six farms, more than 29,000 hectares. We have 2,500 cattle and 2,500 game, and we grow 600 hectares of soya beans, tobacco, wheat and maize for the animals.

The government says there is enough maize for everyone, but people don’t have enough to eat. The food situation is quite desperate in some places. The lean period has been much longer this year, and the climate shocks are more regular.

The problem is that 70% of people are smallholders. They grow maize with subsidies, but then the government pays them peanuts to buy it. Who makes the Zambian smallholder the poorest farmer in the world? The Zambian government.

I just cannot compete with the small guys who pay one quarter of what we do for fertiliser. We commercial farmers get no subsidies. Small farmers are given subsidies for fertiliser and the government buys their maize, but if the subsidy system was reformed, Zambia could grow food for the whole of Africa. It is big, well-watered and has good soils. There is a hell of a lot of potential. We could grow a million tonnes of maize, just like that.

This country cannot subsidise farmers all the time. The guy working with a hoe and oxen is still struggling, and will stay struggling. Meanwhile, commercial farming production has gone down from 400,000 tonnes of maize a year to 30,000.

I have to make a big profit because I need big machines. I spent $500,000 on a combine harvester last year. It’s a John Deere, all computerised: precision farming. I employ 150 men and 80 women for between six and eight months of the year, mainly for packing and grading tobacco. The tobacco buyers are thugs and swindlers.

Genetically modified crops would be a disaster here. They would not produce more food, and they use so much herbicide that the roots burn. I am totally against Monsanto, which will hold farmers by the neck. You can’t put genetically modified trout genes into a cabbage. They are playing God and will destroy the world.

Farai Munyanyi is head of global seed and chemical company Bayer Crop Science in Zimbabwe. We have breakfast at a hotel in Harare. He is pictured with a full English breakfast.

We are a global crop science company [which has offered $65bn to buy out Monsanto], but we don’t profit from droughts like this. We lose money: crops fail and farmers buy fewer chemicals and seeds.

We argue that if people in southern Africa had used our technologies, this food crisis would have been reduced. All the indications are that climate change is here for real, so farmers need drought-tolerant, early-maturing, better seed varieties. They need to know the best time to plant, and how to deal with new pests. We show them that if they use our products on their vegetables, they can do 100% better. But the gap between big and small-scale farms here is very wide. The big ones get eight tonnes of maize per hectare; the small ones just 800kg. They need to change.

Kristof Nordin is a farmer and co-founder of Never Ending Food, an organisation that teaches local farmers about diversifying crops. We meet early evening at his house near Lilongwe, Malawi.

Look what we dug up today – a 21.8kg yam. This is meant to be a drought and the hungry season, but we are growing 200 different foods here – oranges, pineapples, tomatoes, blackjack, maize, sweet potatoes, cassava, millet, you name it. People are begging for food, but we can feed three families throughout the year on next to no land, and have enough left over to sell in the markets.

My wife Stacia is a nutritionist and I am a social worker. We have been in Malawi since 1997, when we came from the US to do HIV-prevention work with the US Peace Corps. We realised we couldn’t address a disease that attacks the immune system without addressing the fact that those immune systems were badly compromised by malnutrition.

There is absolutely no reason for these food crises. The problem is that everyone is focused on growing and eating maize. Malawi has spent 60 years trying to get this Central American food to grow in Africa, and there has been a deliberate stigmatisation of African food. Everything in the west is said to be best; everything from Africa bad.

So we set up our organisation Never Ending Food, and we do internships. We try to show people how to get the most out of their resources, how they can save money and heal the soil. Malawi has a 12-month growing season, access to water and almost 600 local food crops. Yet Malawian farmers are growing only one crop: maize.

This is a tropical country. We should be sending food everywhere. Instead, the US and others are spending millions of dollars on “humanitarian” food aid. It is crazy.

Keith Domleo is agriculture manager of Illovo Sugar, Africa’s leading sugar producer. We met for coffee at the mill in Nchalo, Malawi.

We have 13,000 hectares of land but we contract more so we are now growing food on 18,200 hectares. We send sugar to Sainsbury’s, to Europe, to the US, all over.

We usually grow about 60 hectares of maize a year and donate it to orphanages. But this year the government asked us to grow 2,000 tonnes to help with food supplies. They undertook to supply us with seeds, chemicals and fertilisers.

We grew it on 450 hectares. The crop was good but they still haven’t paid us. We had an unhappy meeting with them so we won’t give them the maize until they give us the money. I am sure it will be resolved.

You can’t feed a country using smallholder farmers. You have to have large commercial farmers. We irrigate everything so we are protected. The small farmers get wiped out in a drought like this.

Felix Pensulo-Phiri is Malawi’s director of nutrition, HIV and Aids in the health ministry. We met for a morning coffee, in Lilongwe.

We are already seeing increases in the numbers of children with acute malnutrition, and as we approach January, February and March these numbers will double. Lives will be in danger.

[The crisis] will have an enormous long-term impact. Pregnant women won’t meet their dietary requirements. Malnutrition can compromise the development of children, affect their brain development. Almost 1 million under-five-year-olds are at risk of stunting, which cannot be reversed.

The social effects will be important, too. At times like this, there is lots of abuse of women. People become desperate. They want food. To access food, men may require women to sleep with them.

It affects school attendance, too. A family with no food will not send children to school. If they do go to school hungry, their performance will be compromised.

This crisis shows that we eat too much nsima – therefore we don’t meet our dietary needs. If we go into irrigation, the country has the potential to feed itself – and other countries, too. The government could supply mechanised, irrigated farming. There are other good foods. Sweet potatoes are easy to store, cassava is drought-resistant, there are places to grow rice. We absolutely must diversify.

David Phiri is chief of the UN Food and Agriculture Organisation in southern Africa. We met for lunch at the Harare sports club, Zimbabwe.

This is a huge catastrophe. A great shock to the system. Hundreds of thousands of people are on the brink of famine. We may see deaths in some places from starvation. The cost of inaction or further delaying our response is too ghastly to contemplate.

We reckon 40 million people across the whole of southern Africa are affected. The worst places are Madagascar, the Democratic Republic of the Congo, Malawi and Zimbabwe, but there are other countries in trouble.

This is the strongest El Niño in 35 years. Smaller droughts in the 1950s resulted in many deaths. The situation could have been much worse, but the biggest risk is in Madagascar. It needs immediate action.

I think the total cost will be $2.9bn, but we are only about 40% funded. We expected more money to have been pledged by now but we understand donor budgets are limited.

Our fear is not a widespread famine, but hotspots of dire hunger. People have exhausted all their reserves now and their coping mechanisms. If food does not arrive, it will lead to serious issues, like childhood stunting, which have lifelong impacts. Even if people recover, they will be prone to cardiovascular diseases.

The relief effort could all go very wrong. I get scared that the rains will come and seeds will not have been distributed. Donors want to do things but it takes them months to act. People give money very close to the rainy season so we must pre-position the food before the money comes in.

We have to start thinking differently about food in Africa. This region was the breadbasket of Africa, but I think we will have more and more crises like this. As temperatures increase, we will see more diseases. We should start to assume there is going to be a disaster every year.

• This article was amended on Wednesday 21 December to reflect that Phiri’s meal included sadza, rather than nsima