The world should wake up to the dangers of the mass production of biofuels, which are increasingly seen as a major solution to global warming, according to Professor Sir Peter Crane, director of the Royal Botanic Gardens, Kew.
Extensive production of biofuel crops, such as oil palms, could destroy remaining areas of rainforest and bring about a new cycle of worldwide intensive agriculture involving vast applications of artificial fertilisers and pesticides, and requiring enormous water resources, said Professor Crane, who as the head of Kew Gardens is the world's leading plant scientist.
"There are big opportunities with biofuels, but there are big problems too," he said. "It's not a free lunch."
Professor Crane, 52, is retiring from Kew after seven very successful years to take up a chair at the University of Chicago, and gave his biofuels warning as part of a valedictory interview with The Independent.
It comes at a critical moment. The production of road transport fuels made from crops, which do not add to the greenhouse gases causing global warming, is now starting to take off around the globe, and is likely to grow vastly. It will be one of the main agricultural developments of the 21st century.
The attraction of biofuels in the fight against climate change is that they are "carbon neutral". Unlike the fossil fuels, oil, gas and coal, which when burnt add to the net amount of carbon dioxide in the atmosphere, the CO2 which biofuels produce when ignited has been absorbed from the atmosphere by the crops used to make them, and so the net atmospheric amount is not increased.
The best known biofuels are ethanol, a petrol substitute made from sugar cane, sugar beet or maize, widely used in Brazil and coming into use in many other countries, and biodiesel, which is made from oil palms, oilseed rape or recycled vegetable oil.
American output of ethanol from maize is now rising at 30 per cent a year; Germany is raising output of biodiesel by nearly 50 per cent a year and China has built the world's biggest ethanol plant. Britain jumped on to the biofuels bandwagon this year with an obligation on British petrol companies to blend a fixed proportion of biofuels with all the petrol and diesel that they sell on garage forecourts. But Sir Peter sounded a strongly cautionary note about the new developments. "If we're serious about biofuels, we're going to have to produce them in a much more sustainable way than intensive agriculture has given us in the past," he said.
He voiced a concern which has already been highlighted by some environmental groups - that mass expansion of biofuel production might lead to a new round of rainforest destruction, especially with crops such as oil palm. Oil palm needs warm humid conditions and is largely grown in south-east Asia on land from which rainforest has been cleared. "Expansion of oil palm production is going to have to be handled extremely carefully to ensure that it doesn't start to eat into the remaining pieces of rainforest that still exist," Professor Crane said.
He went on: "We're going to have to get biofuels off land that's already degraded, perhaps land that's not valuable for other purposes, for conservation or for agriculture. And we've got to do it without creating other problems with the kinds of inputs that in the past have gone into intensive agriculture."
It was possible that intensive biofuel production might involve too much nitrogen-based fertiliser, pesticides and herbicides, in order to get the desired level of production, he said, as well as taking up enormous amounts of scarce water in irrigation.
Sir Peter will be succeeded as director at Kew by Professor Stephen Hopper from the University of Western Australia. In his timeat the Royal Botanic Gardens he has been one of the leading figures in world plant conservation, and was a principal architect of the UN's Global Plant Conservation Strategy.
Under his direction, Kew has been leading the way in one of the strategy's first aims - to provide a working checklist of all the plants of the world.
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