From the BBCAs the world's population grows, competition for food, water and energy will increase. Food prices will rise, more people will go hungry, and migrants will flee the worst-affected regions.
That's the simple idea at the heart of the warning from John Beddington, the UK government's chief scientific adviser, of a possible crisis in 2030.
Specifically, he points to research indicating that by 2030 "a whole series of events come together":
- The world's population will rise from 6bn to 8bn (33%)
- Demand for food will increase by 50%
- Demand for water will increase by 30%
- Demand for energy will increase by 50%
He foresees each problem combining to create a "perfect storm" in which the whole is bigger, and more serious, than the sum of its parts.
"Can we cope with the demands in the future on water? Can we provide enough energy? Can we do it, all that, while mitigating and adapting to climate change? And can we do all that in 21 years' time?" he asked the SDUK 09 conference in London, in March.
Some of the problems reinforce each other, in obvious ways. For example, intensive agriculture swallows up large amounts of water and energy.
But Professor Beddington also points to other complicating factors and worrying possibilities.
There is a risk that climate change will have drastic effects on food production - for example by killing off the coral reefs (which about 1bn people depend on as a source of protein) or by either weakening or strengthening monsoon rains.
Also, some scientists are predicting that the Arctic will be ice-free by 2030, he points out, which could accelerate global warming by reducing the amount of the sun's energy that is reflected back out of the atmosphere.
Not only is the world's population predicted to grow (until the middle of the century, at least) but more people are moving to live in cities, Professor Beddington points out. The growth of cities will accelerate the depletion of water resources, which in turn may drive more country dwellers to leave the land.
As people become wealthier in some parts of the world, such as China and India, their diets are changing. They are consuming more meat and dairy products, which take more energy to produce than traditional vegetable diets. Like city dwellers, prosperous people also use more energy to maintain their lifestyle.
The more land is devoted to growing biofuels, in response to climate change, the less can be used for growing food.
Source information: Energy data graphic derived from World Energy Outlook © OECD/IEA, 2008, figure 2.2, p. 81 and modified by BBC News.
Professor Beddington says he is optimistic that scientists can come up with solutions to the problems and that he is encouraged by signs that politicians are listening more to scientific advice.
But he adds: "We need investment in science and technology, and all the other ways of treating very seriously these major problems. 2030 is not very far away."
Labels: climate changes, environment, science, societal changes, we're fucked