Billions more investment is needed in agriculture and food distribution systems around the world in the next few years, if widespread hunger is to be avoided, according to a group of leading scientists.

If that investment is directed towards sustainable forms of agriculture, then farming can also be made into a weapon in the fight against dangerous global warming, they said, as more environmentally friendly farming methods can result in soils absorbing carbon dioxide rather than releasing it.

Agriculture has been neglected in international climate changenegotiations, but if governments persist in ignoring the problem then millions are likely to go hungry, according to a new report published on Wednesday morning, before the next round of negotiations in South Africa later this month.

“If you intensify agriculture to produce more food while producing less [greenhouse gas emissions] then you deliver benefits in terms of climate change as well – reducing emissions and increasing food security in vulnerable regions,” said Sir John Beddington, the UK’s chief scientist and one of the authors of the report, Achieving food security in the face of climate change, published by the Commission on Sustainable Agriculture and Climate Change, convened by the Consultative Group on International Agricultural Research.

Sir John added: “We need a socially equitable and global approach to produce the funding and policy initiatives that will deliver nutrition, income and climate benefits for all.”

Investment should be targeted at the regions most vulnerable to climate change, as they are also the areas at greatest risk of food insecurity, the scientists said.

Another vital factor in improving food security is to reduce waste and improve food distribution systems. As much as half of the food produced is wasted before it reaches market in some developing countries, because of a lack of infrastructure such as refrigeration systems and reliable transport networks.

Waste is a problem not confined to the developing world, however – cheap food in the developed world has led to a culture of waste that means billions of tonnes of perfectly edible products are thrown away each year. The UK’s Waste Resources Action Programme said this week there had been a sharp fall in household food waste, by 13% in the past year. But waste remains a serious problem – in the UK alone, at least £12bn worth of food is thrown away each year. Campaigners are preparing for an event in London on Friday to “feed the 5,000″, using misshapen vegetables rejected by retailers to illustrate the enormous waste of edible food that takes place in the UK each day.

The scientists also called for a change in consumption patterns “to ensure that basic nutritional needs are met and to foster healthy and sustainable eating habits worldwide”. An increasing amount of food production is geared towards feeding livestock, as people like to eat more meat as they grow more affluent.

The scientists also called for governments to create “comprehensive, shared, integrated information systems” on agriculture. But they said that the demands of an increasing global population for more food could be met without environmental harm, if farming methods were reformed and farmers educated in sustainable techniques.

Agriculture is likely to play only a minor role at Durban, where the next round of international climate change negotiations start at the end of November. Countries are hoping to sort out some of the details of a new agreement on climate change, such as how to ensure a flow of public and private sector finance from rich to poor countries, to help them cut greenhouse gas emissions and tackle the effects of climate change.

Ronald Reagan was coming to the end of his second term in the White House, and though embroiled in the Iran-Contra affair, had just challenged the Russian president Mikhail Gorbchev to tear down the Berlin Wall. Margaret Thatcher had won a landslide victory at the polls and returned triumphant to Downing Street for a third term.

It was the year the Dow Jones Industrial Average broke through 2,000 points for the first time (it is now over 11,000), while the UK music charts bopped along to the sounds of Whitney Houston, Duran Duran and Samantha Fox.

1987 was a different and less crowded world. On 11 July, the UN named Matej Mitja Gašpar, born in Zagreb, Croatia, the 5 billionth human being alive on the planet. To make sense of the milestone, the Guardian invited the Norman Myers, the celebrated British environmentalist, to make sense of the moment in our global family’s history. In the 24 years since his words below were published an extra 2 billion souls have been added to the planet. Myers speculated about returning the global average fertility rate to replacement levels – around two children per couple – by 2000 and keeping the planet’s population peak to 8 billion – something he acknowledged would be a “mammoth task”.

Nearly a quarter of a century hence it is clear we have failed to get close. Global population will add at least another 2 billion before dropping back. But the issues he raises for humanity to tackle – agricultural capacity, resource scarcity and the “greenhouse effect” – have only become more pressing. As Myers puts it: “We shall need to do an enormous lot of things right, and all at once.”

World without end? Amen – by Norman Myers, 4 Jul 1987

On 11 July, the United Nations has determined that the human population will reach 5 billion people. The UN won’t designate the hour of that momentous day, nor the gender of the infant.

But while the arrival of the baby in question will be a cause for celebration for the parents, it is a matter for commiseration for the rest of us. Every day there is more evidence that the planet is groaning under its efforts to support its present burden of humankind.

The problem is not the intrinsic capacity of the Earth to support 5 billion. There are sound calculations to the effect that it could eventually support four times as many, perhaps many more still as we harness technology to make the deserts bloom, and all that. But this depends on our doing things right, and not just in expanding our agriculture. Twice as many people are expected to need three times as much fibre as well as food, and four times as much energy. In fact, we shall need to do an enormous lot of things right, and all at once. Yet we show a continuing capacity for doing things less than perfectly.

The essential problem is that the Earth is taking on board additional people at a rate that far exceeds the capacity of societies to plan for them. Even the most advanced and well organised community would find it taxing in the extreme to accommodate more people at a rate of 2% per rear for decade after overloading decade.

Britain never had to attempt it. When we were a developing country in the last century, we had to handle a population growth rate that rarely approached 1% and when things got a bit tight economically, we simply despatched the surplus to our dominions and colonies overseas. When the Americans had a growth rate of more than 1%, they could indulge the cry of “Go west”. Today the developing countries average growth rate of around 2.5% a year, and for the most part they have run out of wests to expand into.

It is the exponential impact of population growth that causes trouble.

Not everybody appreciates the in-built dynamics of “demographic momentum”: a growth rate of 3% sustained for 100 years produces an ultimate population that is 19 times greater than the initial size.

Thus the main population explosion – or to give it its proper name, the population implosion – is still to come. It has taken 13 years for us to climb from four to 5 billion. The next one billion will take us only 12 years, and to reach 7 billion 10 more years. Only then will there be a slow-down, until we reach a projected final total of over 10 billion more than a century hence.

Yet despite many efforts at birth control campaigns, the annual growth rate is still increasing a little. China’s reproductive-age population is bulging as a result of the post-Great Leap Forward baby boom of the 1960s, plus a relaxation of its “one couple, one child” strategy. Well might the Chinese slacken off a little, even though the long-term consequences will be dire, according to the country’s leaders.

The one-child goal clashes with the desire of Chinese with the desire of Chinese parents to have a son – a preference they share with human communities in most places at most stages of history. Result: when the first born turns out to be female, it sometimes ends up in the local stream – a penalty of the delay by China’s earlier leaders to get to grips with population growth soon enough and vigorously enough. This might give pause to Bangladesh, Pakistan, and other countries, many of them Muslim, which let parents decide to do as best they see it at the time.

Some observers assert that rather than seeking to contain the number of people at the banquet of life, we should enlarge the table and place more food upon it. They might consider the prospect of Kenya, with 20 million people today. Kenya’s population features a “youthful profile”, meaning there are many prospective parents coming up through the ranks. Even were Kenya to come down to a two-child family forthwith (instead of eight), it would still reach 53 million people before growth peters out. Yet even were it to institute high-tech agriculture of the sort practised by the Dutch and Japanese, Kenya could not support more than 51 million people off its limited land.

The projected total for Kenya’s zero-growth population is 111 million.

The July 11 infant is likely to be born to developing world parents.

But suppose it were to be an American baby? If it follows the prodigal habits of its parents, it would waste more energy in its lifetime than 20 Kenyans would carefully consume. If it were a British baby, its demand for peanut products and cotton would stimulate the growing of export crops in the Sahel, which tends to drive landless peasants into arid lands where they foster the spread of desert.

Each time we (well, you) climb on to our weekend yacht, we might speculate that much of the high quality timber has come from tropical forests. The price paid for the timber does not reflect all costs that go into its production in those forests especially over-cutting and other environmental damages. Our fossil fuel binge is the main source of the “greenhouse effect” that promises to disrupt climates for communities throughout the world. All too unwittingly but effectively and increasingly, developed world citizens contribute to the rundown of the planet’s natural resources that sustain everyone’s welfare. It is the super-rich 1 billion that do as much damage to our Only One Earth as the super-poor 1 billion.

Yet there is good news too. There are splendid opportunities to reduce birth rates with massive advantages. If the global community were to achieve a replacement level of fertility – namely a two-children family on average – by the year 2005, or 21 years earlier than the United Nations assumes in its medium projection to be a realistic target, the ultimate global population would stabilise at around 8 billion persons, or more than 2 billion fewer than the projection.

If replacement levels of fertility were not reached until 20 years later than anticipated, 2.8 billion people will be added to the projected global total. The difference of 4.8 billion is almost as many people as there are on Earth right now.

To reduce the fertility rate to replacement level by the year 2000 would be a mammoth task. But it would be by no means impossible, as witness the startling declines on the part of certain communities in Taiwan, South Korea, Java, Thailand, Kerala State in India, Sri Lanka, Cuba, Mexico, Costa Rica and Colombia, during the recent past – these being countries that represent a broad range of political and economic systems, as well as of social and cultural backgrounds. If Nigeria, for instance, were to achieve that goal, its ultimate population size would not be 532 millions but 227 millions – with a host of expanded options for the nation’s sustainable development. The Indian sub-continent’s total, now projected to reach 2.4 billion, would be reduced to 1.8 billion.

To reduce the fertility rate, most couples have to be provided with motivation as well as “contraceptive hardware” which is why the overall task is daunting. But we could make a solid dent in the problem by merely taking care of the needs of women who want fewer or no more children, but who lack family planning facilities. According to various surveys, the proportion of women with such unmet needs ranges in different countries from 11% to 29%. Suppose we accept a rough average, for the sake of a working approximation, of 20% of the 400 million women “at risk” in developing countries, or 80 million in all: even this relatively small number would be enough to reduce the ultimate population by many hundreds of millions.

To supply contraceptive services to these women would add, at an average cost of $12 per head, only another $1bn or so on top of the present annual family planning expenditures (China excepted) of about $1 billion. That sum is equivalent to one third of one day’s military spending worldwide. Which would buy us the more all-round security?

If you believe the doomsday merchants, the scariest thing about this Halloween is the fact that the world’s population will pass seven billion on or near October 31.

Population growth, however, is not the biggest skeleton in the closet when it comes to our planet’s ability to absorb human impact. Far more damaging than the booming birth rate in low income countries are the resource-intensive lifestyles of the global rich and middle class.

Contrary to popular belief, reducing the global birth rate would not make a big dent in the amount of fossil fuels, minerals, and timber we use up. For example, if the 1.3 billion people who lack electricity today were all able to tap basic lighting and heating services by 2030, world energy demand would rise by a mere 1%, according to the International Energy Authority (IEA).

Contrast that with the destructive impact of middle class lifestyles on natural resources. In 2008, the United States consumed 39 times as much energy per person than Bangladesh, while citizens across all high income countries consumed 14 times more energy than those of low income countries.

What’s more, population growth is slowly leveling off (and will be concentrated in Africa) while the global middle class is expanding exponentially. According to Goldman Sachs, 70 million more men and women enter the middle income bracketevery year. By 2020, The Economist recently predicted, China’s economy is likely to outgrow that of the United States. And India is only a few decades behind. Meanwhile, 60% of the Earth’s ecosystem services - the very resources that underpin our modern lifestyles – are already deteriorating under our over-exploitation.

All this is not to suggest that hard-earned middle class lifestyles must be curbed or that Africans and Asians should be denied the chance to own laptops and iPods. Far from it. Instead, as the middle class grows, business and governments need to find ways to shrink natural resource use, and ultimately decouple it from lifestyle and economic growth. This may sound a tall order, but there are several vitally important areas, including food supply and water use, where we can make a good start today.

Population change between 2010 and 2100 by major region (millions). Source: United Nations, Department of Economic and Social Affairs, Population Division (2011). World Population Prospects, The 2010 Revision. (Click to enlarge)

First, food. Worldwide, at least 30% of all food grown is lost between field and fork. In developing countries, this waste typically occurs post harvest when poorly secured crops are degraded or eaten by pests. In the developed world, consumers and the food services sector are the main culprits, throwing out mountains of uneaten perishables. How do we fix this? For consumers, education and awareness campaigns that help change wasteful habits can make a big difference on a national scale. In developing countries, simple and relatively inexpensive approaches, such as improving grain storage by building local construction skills can pay dividends. In Afghanistan, for example, such measures cut post-harvest crop losses from 20% to 2%.

Second, water. Rising water demand is outstripping supply, driven in part by the land and water-intensive needs of meat-heavy middle class diets. By 2025, 1.8 billion people will be living in water-scarce countries or regions, with alarming implications for human wellbeing and global security. With agriculture responsible for 70 percent of all freshwater use, we urgently need to find ways to produce more crop per drop.

Drip irrigation is one proven solution, increasing water use efficiency by as much as 40 percent compared with flooding fields indiscriminately with water. Other efficiency measures such as modest shifts in cropping patterns and smart irrigation scheduling also reduce the amount of water pumped for farming, and save energy and related GHG emissions in the process.

Population growth is not a negligible issue. In many local communities, it will undoubtedly cause resource crunches, human hardship and policy challenges. In the Sahel and parts of South Asia, for example, birth rates are soaring while ecosystems services such as water, wood and healthy soil are increasingly scarce. But on a planetary scale, high consuming lifestyles are a bigger problem.

Taking the kinds of corrective actions suggested above, on a global scale, is practically possible and would not cost the Earth. But not taking them might. Now that really is a scary thought.