It's true that times are tough. Thanks to the sub-prime crisis and issues like the global credit crunch, many economies are in poor shape. Oil prices are continuing their upward spiral and rose by about 400 percent between 2001 and 2008. And food cost increases are affecting most countries around the globe, with prices for dairy products up 80 percent, cooking oils up 50 percent, and grains up 42 percent from 2006 to 2007.

As a result, it's already been suggested that tax increases designed to wean us all off fossil fuels are at least postponed, if not abandoned. The fear expressed by some is that they will drive the developed world even deeper into recession. Commentators point to events like the World Economic Forum in Davos in January, where some argue that climate change was bumped off the agenda by the turmoil on the world markets.

I'd argue, however, that people -- and companies -- who think sustainability is merely a fair weather exercise have been missing the point all along. Indeed, as environmental entrepreneur Shai Agassi comments, the lack of an official green agenda in Davos is actually a good sign. He says: "It just shows that we are off the hype curve and into solutions."

And as Lord Stern, former chief economist of the World Bank and author of the U.K. Treasury's Stern Review on the Economics of Climate Change said recently: "I think that difficult times should not derail this. There will be some ups and downs over the next fifty years but we have to push through that."

He's right. When times are tough, the onus on every business is to save money, protect and build revenues and make sure core business assets are being fully utilized. Running your business in a sustainable way can be a key driver when it comes to meeting your goals -- not just when times are tough, but actually because they are tough. In fact, I'd say there are three main reasons to ramp up your sustainability efforts when times are hard.

Firstly, it's a good way of responding to the three 'Rs' -- revenue, reputation and regulation. Take revenues. In times of rising prices, businesses need to manage their supply chains and business processes to ensure maximum productivity.

According to McKinsey: "most companies in most sectors have profitable opportunities to save money by cutting energy consumption and gas emissions. Our studies indicate that a lot of companies can reduce them by 20 to 50 percent." Pfizer, the pharmaceuticals company, for example, saved $30 million a year between 2002 and 2005 with its program to cut energy wastage and use more power from renewable sources.

There are other ways to cut costs by running your company in a sustainable way too. According to Fortune Magazine, the retailer Wal-Mart found that it could save $26 million a year on its fleet of 7,200 trucks by installing auxiliary power units. These enable the drivers to keep their cabs warm or cool during mandatory ten-hour breaks from the road. Before that, they'd let the truck engine idle all night, wasting fuel. Wal-Mart also installed machines called sandwich balers in its stores to recycle and sell plastic that it used to throw away. Company-wide, the balers have added $28 million to the bottom line.

Then there's reputation. Abandoning environmental commitments can have a big impact on how a company is perceived -- not something that any firm wants to attract when facing financial pressures, particularly when we live in world in which a 2007 survey of MBA students quoted in the Financial Times found that "77 percent of them would willingly forgo income to work for a firm with a credible sustainability strategy".

Indeed, just because times are tough doesn't mean customers have altered their behavior. Particularly when times are hard, they still want to see companies doing the right thing, environmentally, economically and socially. How would customers respond if, for example, for Marks and Spencer, the U.K. retailer which announced Plan A, a $400 million plan to become carbon neutral in five years, in January 2007 abandoned it because of fears of recession?