Biofuels or forests
By Professor Renton Righelato
Former Chairman of WLT Trustees
Over a quarter of CO2 production globally comes from transport and moving to carbon-free transport fuels presents some of the most difficult technical problems. While there are solutions like hydrogen in the offing, it will probably be 30 years or more, before the bulk of transport fuel could be replaced. Liquid biofuels offer a superficially attractive option because they can be used by existing cars and lorries and use the existing fuel distribution system. Powerful agricultural lobbies have seized on this as a substantial growth opportunity and governments see it as way of reducing dependence on oil imports or as a large export opportunity. In Europe, biofuels are seen as a way of meeting the EU “renewables” obligation. We believe that the current rush into biofuel production is misguided – it is a risky and ineffective strategy for reducing CO2 levels and it is destroying natural habitats rich in biodiversity.
Production of biofuels itself uses fossil carbon (for fertilisers, fuels, buildings etc), so in most cases the use of the biofuels spares only a half or less of the emissions of the fossil fuel. The land dedicated to fuel production would be many times more effective at mitigating CO2 levels if it were restored to natural forest. When arable land is restored to forest instead of growing cereals, oil or sugar crops for biofuel production, carbon stores build up in the soil and vegetation and outweigh the emissions avoided by the production of biofuel. For example, replacing cropland with tropical forest can sequester 20-30 tonnes CO2/hectare per year-6, three to four-fold higher than the emissions avoided by using bioethanol from a hectare of sugar cane.
Conversely, when natural forests or grasslands are cleared and replaced by arable land to produce the fuel crop, the loss of carbon stored in the biosphere is huge. In the tropics, the amount of carbon released into the atmosphere by converting forest to cropland is approximately 600-800 tonnes carbon dioxide per hectare. This occurs through burning and biodegradation in the months following the initial clearance and its impact on global CO2 and warming is immediate. It would take a century to balance this loss of carbon from the savings made by biofuels. On top of that, removal of forest cover can reduce downwind rainfall, causing a cascade of further forest loss, further reducing the biosphere’s capacity to sequester carbon and accelerating warming.
The World Land Trust is also concerned that replacing diverse natural habitats with monocultures of arable crops dramatically reduces the range of plants and animals that an area supports. This is particularly true in the tropics where the forests are the most biologically diverse regions on the planet and where forest loss has already eliminated or endangered many species. So, as well as protecting standing forests, we are restoring forest on previously cleared land – both extending valuable habitats and helping sequester carbon.
- Carbon Mitigation by Biofuels or by Saving and Restoring Forests? (Summary) (Full text) Renton Righelato and Dominick V. Spracklen, Science Vol. 317. no. 5840, p. 902
- Climate Change and Nature Conservation: What the World Land Trust is doing
- Press release 16th August 2007: Biofuels Costing the Earth?