EVERY meal, the average person "eats" 1.3 litres of diesel fuel, 10 kilos of soil and 800 kilos of fresh water - in the form of food.
That is what it takes to feed the typical human being, according to science writer Julian Cribb, who was one of the key speakers at the Queensland State Landcare Conference in Warwick on Friday.
"When you multiply it by 7.2 billion people, our food system is devouring a huge amount of resources that are increasingly hard to replace," Mr Cribb said.
The risks to the global food production and a safe human future are very great - but if we recognise them and act soon enough, then the opportunities, including diversification into alternative crops, are very great.
"For the average person, eating is probably their largest personal impact on the planet - but almost nobody realises how big it is."
The author of The Coming Famine: the global food crisis and how we can avoid it, also warned of 'tipping points' - dangerous points of no-return - that will be reached by the global food system in the coming half century, unless there is radical change to farming systems, cities and the world diet.
"Take soil. According to the UN Food and Agriculture Organisation, half the planet is already degraded, and we're losing around 75 billion tonnes of topsoil a year, mostly into the oceans. Soil takes thousands of years to form, so it is not going to be replaced soon," Mr Cribb said.
"Despite progress in places like Australia, soil degradation is getting worse. Some scientists say we could run short of good farming soils within 50-70 years. This is what's driving the global land-grab - which has so far swallowed an area as large as Western Europe."
Mr Cribb said the picture was similar for water, with more than 4000 cubic kilometres of groundwater being extracted every year. Places such as north China, the Indo-Gangetic region, the Middle East and Midwest USA face critical scarcity by the 2030s.
At the same time there is a huge worldwide grab by megacities and gas companies of farmers' water - making the task of feeding the world much harder.
"Regardless of when you think peak oil is or was, world car production is growing 10 times faster than oil production - major oil shock is increasingly likely," he explained.
" Since food accounts for 30% of global energy use, there could be a large impact on farming and world food prices."
However, Mr Cribb said, what most governments and commentators on food security have failed to recognise was that scarcities of water, land, oil, nutrients, technology, fish and finance are now acting in synergy - and being amplified by climate shocks.
"Because these scarcities are in sync, we may reach tipping points in the food system more quickly and unpredictably than people realise," he explained.
"There is time to act - but the action must be fast and universal, as globalisation means everybody is affected by food prices, supply and the conflicts and refugee tsunamis that arise when the food chain fails.
"It is time we put Landcare and NRM on a war footing, worldwide."
Mr Cribb also said there were opportunities for major new developments in food production, including a $50 billion new industry for Australia in algae farming to produce food, feed, fuel and plastics, a spectacular rise of urban agriculture and totally new ways to produce low-cost food sustainably with bio-cultures.
"There are also 25,000 edible plants on Earth, 99% of them unfamiliar to most people - so we have not yet begin to explore the culinary potential of our home planet. This is going to be a very exciting time for new, healthy, interesting and sustainable diets and farming systems," he said.
"Australia alone has 6100 edible plants of which we currently eat just five or six.
"My message is that the risks to the global food production and a safe human future are very great - but if we recognise them and act soon enough, then the opportunities, including diversification into alternative crops, are very great.
"In Australia, for example, we have opportunity for new food and farming industries worth $50 billion and employing around 50,000 people - provided we get our science, our investment and our act together."