In short supply in many parts of the world, water will be come even more scarce as demand grows. Average consumption in the UK, at 146 litres per person a day, is only slightly less than the 152 litres used daily 15 years ago.
The heatwaves and water restrictions of recent years have, however, encouraged some, such as 34-year-old Neil McNiven, an electronics engineer from Kidwelly, Carmarthenshire, to do more to save water.
"I started collecting rain in various water butts. Using a couple of gadgets we now also capture water from showers and baths to use for car washing and window cleaning, and we use rainwater for our toilets instead of mains water. We also started doing all the usual water-saving techniques such as turning the taps off when brushing our teeth and rinsing greasy pans with the boiling pasta water. Whereas before we'd been using mains water for everything, I'd estimate we reduced our mains water consumption by at least half, and we could have halved it again with rainwater toilet flushing ... it is a lot cheaper to reduce the amount of water and electricity you use rather than continuing to be wasteful and trying to meet your inflated requirements with renewable sources."
Talked up as a renewable form of power for decades but yet to fulfil its potential. Many people are put off by the cost and complexity of getting wind turbines installed. Only about 1GW of new wind power generation was turned on in 2009, an annual figure that needs to triple by 2020.
John Martin, a 64-year-old engineer from Wickford, Essex, is an "early adopter" of the technology. He had a 16-metre high wind turbine fitted in his garden last December.
"High on my priority list was to reduce my electricity bills as far as possible. I am also wary about the future, when electricity is going to be a lot more expensive than it is now. I must be very candid and say that environmental factors were not high on the priority list, but it does help. It's really a matter of taking the least amount of power from the national grid as possible. My turbine has the potential to produce 24,000kWh a year but there has been so little wind this year that, to date, it's generated only about 1,000kWh."
Once seen as a minority pursuit confined to green activists, recent years have seen recycling move into the mainstream. Some 38 per cent of household waste is now recycled – with an EU target for this to rise to 50 per cent by 2020.
Rachelle Strauss, 38, from the Forest of Dean in Gloucestershire, is one of the growing army of Britons who now recycle their rubbish. The married mother of one was inspired to start recycling after her family was caught up in the Boscastle floods of 2004, which awakened her to the realities of global warming.
"Following the floods I wanted to do something to assuage my guilt about global warming, so I began recycling. Last year we had just one dustbin worth of waste, and the aim next year is to send absolutely nothing to landfill. To achieve this we buy a lot of our produce locally and in bulk so that there is no need for packaging. We also take our electronics to the local refuse station which can recycle them. I will send stuff to companies asking them what it is made of so I can find out how to recycle it."
One of the simplest ways to save energy, yet millions of Britons have yet to get their homes properly insulated. According to figures from the Department of Energy and Climate Change, up to a third of the money spent on gas and electricity is lost through poor insulation. And the Committee on Climate Change says that 10 million lofts and 7.5 million cavity walls need to be insulated by 2015. The Government's 'Green Deal' for households aims to encourage home energy efficiency improvements, paid for by savings from energy bills.
Proper insulation has long been a top priority for 73-year-old Janet Alty from Leamington Spa.
"When my husband and I first moved into our house in 1965 we felt very noble because we put two inches of insulation into the roof; at that time the rule was one inch! Now all our loft insulation is more than 10 inches. Some of the external walls also have internal insulation and internal secondary-glazed windows have been fitted on approximately half of the windows. ... Decorating your house with 'eco-bling' will not work unless you have already done everything possible to reduce your carbon footprint by becoming as energy efficient as possible."
The farming industry is a major contributor to greenhouse-gas emissions and increasing awareness of the carbon cost of the food we eat is seeing a growing demand for locally produced and sourced food.
The link between her diet and the environment is very clear to Margot Hanley, a 22-year-old art student from London.
"I became a vegan two years ago while studying at a university that had a strong environmental programme. People don't think about the effect of meat production on land usage, water pollution, deforestation and grain shortages. In Britain, 70 per cent of all agricultural land is used as pasture and to grow crops to feed animals. A lot of that land could be used to produce food that humans could eat ... I am on a tight budget as a student so I mostly shop in supermarkets but I try to check the origins of the food and eat seasonally and locally. I chose this method of improving my impact on the environment because I think we are at our most powerful as consumers. I think the best way to bring about the progress we want to see is to change what we consume, which in turn changes what is produced."
Government targets commit to keeping aviation emissions at 2005 levels up to 2050. But this will require limiting demand for flights so that passenger demand is not increased by more than 60 per cent by 2050, according to the Committee on Climate Change. And between 1990 and 2009 carbon emissions from aviation fuel more than doubled to over 34 million tons.
Ciaran Mundy, a 41-year-old father of one from Bristol, is an environmentalist who founded the lowflyzone.org website. He has not flown since 2007.
"Now, knowing what kind of damage it causes to the environment, I don't think I could ever fly again. I can't bear such things as the Deepwater Horizon oil spill being done in my name so I can casually fly to Australia or Thailand for a holiday to enjoying the beauty of nature or a spiritual retreat – the irony is too much ... I also do other things to reduce my carbon footprint: I take the train and cycle whenever I can. However, stopping flying is the most important step in my eyes because one long-haul flight a year doubles an average person's carbon footprint."
The first form of renewable energy to really catch on – thousands of Britons have installed solar panels on their homes. But it still has a way to go, with most of Britain's 25 million households needing solar panels if the Government is to reach its climate-change targets, according to the Royal Academy of Engineering.
Keith and Jenny Sinfield
Solar panels can cost thousands to install. Grants can make all the difference, according to Keith and Jenny Sinfield, a retired couple from Rugby.
"We had a set of solar panels installed three years ago. At that time there were grants on offer which covered half the cost. We then had another set installed last month. With interest rates falling, they represent an excellent investment as the feed-in tariff paid by the Government guarantees a high rate of return. We are also concerned about energy security in the future, so it's good to be a bit less dependent on the grid. It's also easy to be sceptical about the new government's environmental credentials, not least because it has already started to backtrack on Labour's Renewal Heat Incentive scheme, which would have given financial support to people installing things such as solar panels."
Carbon emissions from private cars rose by 6 per cent between 1990 and 2008 and, despite repeated calls for people to use cars less, the percentage of trips made on foot or by bicycle declined from 29 per cent in 1995 to 24 per cent in 2008. But some have made the ultimate sacrifice and dispensed with their gas-guzzling car altogether.
Nick Herbert, 46, whose family runs Hugo's restaurant in Queen's Park, west London, bought an electric car in 1998 to make deliveries and act as an advert for their organic café.
"Originally, we had a milk float instead of a car but when the G-Wiz electric car came on the market we bought one of those. Everyone thought we were crazy because of the limited range it can go on from a charge point. But a full charge from the mains costs around £1.50 and lasts for a whole day – around 45 miles. For personal transport we've all got bicycles and we use those whenever we can. Everything we do is green; it is the whole ethos behind our project. We have always been ahead of the curve."
Household energy consumption increased by 7 per cent between 1990 and 2009, but, with the prospect of rising gas and electricity bills, people are increasingly looking to save energy in the home.
Simply turning electrical appliances off at the mains and installing energy-efficient lightbulbs could cut Britain's carbon emissions by 40 megatons a year – the equivalent of removing about 10 large gas-fired power stations from operation.
James Strawbridge, a 26-year-old environmental trainer from St Austell, Cornwall, is one of a growing band of young people embracing green lifestyles.
"It is a lot more mainstream now. As a motivation factor, it is far less about being green. It is about saving money. You don't have to be rich to be green. One big thing is people think they want to live in an eco-house, and think of a Swedish log cabin, but you can take your own house and retro-fit it with simple things that are much more efficient. The problem is, it is just not as sexy getting a Hippo [water-saving device] for your toilet or insulating your loft as getting a wind turbine on your roof. For normal people who just want to save money on their bills, it doesn't require huge investment."
Energy from waste.........
Converting waste into energy, in a process called anaerobic digestion, may sound too good to be true, but it is a reality. However, the paperwork involved, not to mention the lack of financial incentives, have resulted in a slow take-up of the technology. There are only around 30 anaerobic digestion plants in Britain, compared with more than 4,000 in Germany.
Steven Temple, a 61-year-old farmer from Wells, Norfolk, spent £750,000 on an anaerobic digestion plant to turn slurry and crops into power.
It started producing biomethane gas last Christmas, and a combined heat and power unit has just been connected, with the heat used for cheese-making, grain drying, hot water in the dairy and heating the farmhouse.
"Anything that might conceivably be classed as a waste in some circumstances, even if we don't consider it a waste, the Environment Agency wanted to class it as a waste. If I had known how much regulation and paperwork there would be, I wouldn't have done it. It is putting people off cleaning things up. If I am improving the situation and making it better, I would have hoped I would have had less paperwork."