While many of us here in the UK feast our eyes on an appetising array of food and cookery TV shows and our stomachs on pre-prepared foods, and as our kids are tempted by ever-more cunningly-named cereals from Kraves to Choc'n'Roll, it's hard to reconcile ourselves to the hard facts of food production and sustainability. Probably because we want this basic ingredient of life to remain a sensory object of our desires rather than an everyday concern.

By 2050, to feed the estimated world population of 9 billion, we'll need an annual production of around 3 billion tonnes of cereal and 200 million tonnes of meat. Image © Ellen Goff

But for nearly 1 billion people - one in seven - there simply isn't this luxury as they do not have enough to eat each day. And many more suffer from malnutrition, despite the fact that every human being has a right to adequate food. (I sometimes wonder why some clever bod hasn't come up with a way to recycle and preserve unused food that's chucked out daily from our households, restaurants and workplaces, and which could be supplied somehow to hunger hotspots. Here in the UK we throw away an astonishing 7.2 million tonnes of consumable food and drink each year - enough to fill 4,200 Olympic-sized swimming pools!)

The UN's Food and Agriculture Organisation (FAO) estimates that by 2050 we will need to increase agricultural production by 70 per cent to meet the food demands of a suggested 9.1 billion population (one that is about 34 per cent higher than that of today). But will there be enough land, water and genetic biodiversity to meet the demands?

The FAO also estimates that only about a dozen species of animals provide 90 per cent of animal protein we consume globally, and only four crop species give us half the plant-based colonies in our human diet. Conversely, the gene pool in plant and animal resources and natural ecosystems, which breeders need, is known to be diminishing. In the future we may be encouraged to be more vegetarian or reconsider genetically modified foods such as in vitro meat on our menu. Our breeders and farmers may be asked for alternatives to single crops and to re-evaluate the benefits of industrial as opposed to family farmng. As more people move to the cities, there may need to be more institutionalised plans in place for rural agriculture.

Is there enough water for the crops of the future? Will the need for staple grain crops decline in an increasingly industrialised world?  These and other key concerns of food security and production will be  discussed tonight in our fourth Earth Debate at the Museum.

And how will factors like a much larger urban population and the associated rise in supermarket culture, climate change and biofuels impact on our food security? In what ways can we balance the uneven distribution of resources and the over-nutrition of developed, more industrialised societies with the malnutrition of poorer communities? How much of the problem is one of production rather than managing wastage and taking over more land? And what of population growth checks?

These paradoxes of food and our future food security are the subject tonight of our fourth and final Earth Debate to be webcast and hosted in the Museum's Attenborough Studio and we need your thoughts on the subject too. Stakeholders Forum for a sustainable future will feed - scuse the pun - the discussions on to the big Rio+20 UN Conference on Sustainable Development in June.

On the panel are Sue Dibb, Executive Director of the Food Ethics Council, Barry Gardiner, MP and Chair of the All Party Parliamentary Group on Biodiversity, John Ingram, Food Security Leader at the Natural Environment Research Council and Camilla Toulmin, Director of the International Insititute for Environment and Development. The BBC's Richard Black will be chairing and, as with the previous debates, an invited audience and submissions via #earthdebates on Twitter will lead the questions to the panel.

Watch the Food security: how do we feed 9 billion people in 2050 debate live online at 19.00 BST tonight. If you can't tune into the webcast, we'll also be live-tweeting from @NHM_Live starting at approximately 18.50 or you can follow #earthdebates.

See the other debates online

Find out more about our Earth Debates

Read the Food and Agriculture Organisation's food security report

As I walked through the Museum’s Earth galleries last week it made me chuckle to see a small sign posted on the What is Earth’s future? exhibit. The sign read ‘Out of Order. This exhibit is being repaired…’ The group of young lads who noticed it too were also highly amused at the irony of it.

The Museum's What is Earth's future? exhibit, recently declared 'Out of order'. Symbolic of things to come for our planet? The exhibit, located in the From the Beginning gallery in the Museum's Red Zone, has since been restored to its spinning globe with haunting moving images projected on it. Select images to enlarge them

Of late, we’ve experienced some trying times behind the scenes in the Earth galleries office block, where I work. First our staff lift ground to a halt (leaving us with a lung-busting hike up the stairs), then the water packed up - just as well since the toilets had stopped working - and to top it all off  the heating threw in the towel for a day at the height of the recent cold spell. However, we soldiered on to make the Red Zone's galleries the greatest show of Earth on Earth. And, because we care and because the Natural History Museum is an inspiring place to work, we were happy to do so (like the rest of our 'fairly happy' fellow Britons as recently observed in the much-talked-about Happiness survey.)

It strikes me that what happened in the Museum's Earth galleries is in uncanny synchronicity with the central concerns of our current series of Earth Debates, which continue here over the next three months: if we don’t do some vital repairs to our resources and society, will parts of the Earth soon be declared out of order too? What is the real impact of what we produce and consume on our surroundings? Does our quest for the greatest show, greater monetary wealth and the constant demand for more material goods come before our immediate day-to-day living needs? Are we happier and do we feel more valued if we are more affluent or is it because of what we achieve and where and who we are with?

Would you be willing to go vegetarian, or even just to switch to eating poultry, pork or pasture-fed beef rather than grain-fed beef to reduce the impact of agriculture on the environment? Big decisions are ahead at the next international Earth summit.

There is little point in me trying to explain here why the UN's earth summit in Rio de Janeiro in June is so important (aka Rio+20 as it is being held 20 years after 1992's seminal summit). It would take too long - our Earth Debates partner, the Stakeholder Forum for a sustainable future, who are coordinating and guiding key discussions in the lead-up to Rio+20, has identified 97 key issues (see the tag cloud below) - and besides our Earth Debates pages online already do a very clear job of this and will point you to all the right places for more information.

What's more vital is that the Museum needs your input now on the big issues that will be acted upon at global level in June. We need your thoughts on a sustainable green economy for the world or your local area, and all your favourite bugbears that go with it, as part of our ongoing Earth Debates.

Each of our four Earth Debates, with its four panellists and invited audience, is broadcast live from the Attenborough Studio on our website. The format of each debate is like BBC’s Question Time and you can watch it live, follow or contribute your questions or comments using #earthdebates on Twitter, or post your views to our online community before, during and after the event.

The next Earth Debate is this Wednesday 22 February from 19.00 to 20.00 GMT where the panel and studio audience will ask Beyond GDP - how can we measure progress? This debate will question the alternatives - like measuring our wellbeing and the value of the environment - to the traditional measures of economic growth and and asks what is needed for businesses and governments to invest in a green economy rather than exploit it.

Bookmark the link to the webcast and to #earthdebates on Twitter to join us on the night.

Missed the first Earth debate on 25 January about the price of nature? Watch the highlights in this short video clip which features debate chair Tim Radford, panellists Professor Sir Robert Watson, Claire Brown, Ian Dickie and Will Evison, and audience member Tony Juniper.

'Business as usual is absolutely unsustainable... but we also have to show business that there are solutions.' An extract from the closing comment of Defra's Robert Watson in January's first Earth Debate.

Watch the whole of the first debate Ecosystem economics - can we put a price on nature? (video of the 1st Earth Debate).

The third debate will tackle Green cities in a green economy - how to pioneer a sustainable transition? on 14 March 2012, followed by the fourth debate Food security - how do we feed 9 billion people in 2050? on 11 April 2012.

Find out more online about our Earth Debates and the Rio+20 Earth Summit in Rio de Janeiro

Get more information on the the Stakeholder Forum for a sustainable future and their priority concerns.