The ongoing expansion of oil palm plantations in the humid tropics, especially in Southeast Asia, is generating considerable concern and debate. Amid industry and environmental campaigners' claims, it can be hard to perceive reality. Is oil palm a valuable route to sustainable development or a costly road to environmental ruin? Inevitably, any answer depends on many choices. But do decision makers have the information they require to avoid pitfalls and make the best decisions? This review examines what we know and what we don't know about oil palm developments. Our sources include academic publications and ‘grey' literature, along with expert consultations. Some facts are indisputable: among these are that oil palm is highly productive and commercially profitable at large scales, and that palm oil demand is rising. Implementing oil palm developments involves many tradeoffs. Oil palm's considerable profitability offers wealth and development where wealth and development are needed-but also threatens traditional livelihoods. It offers a route out of poverty, while also making people vulnerable to exploitation, misinformation and market instabilities. It threatens rich biological diversity-while also offering the finance needed to protect forest. It offers a renewable source of fuel, but also threatens to increase global carbon emissions. We remain uncertain of the full implications of current choices. How can local, regional and international benefits be increased while costs are minimised? While much important information is available, it is often open to question or hard to generalise. We conclude this review with a list of pressing questions requiring further investigation. Credible, unbiased research on these issues will move the discussion and practice forward.

Presentation from the session session "Biofuels, Tropical Deforestation, and Climate Policy: Key Challenges and Opportunities" at the annual AAAS meeting, Feb 14 2009.

Recent work has shown that current bio-energy policy directives may have harmful, indirect consequences, affecting both food security and the global climate system. An additional unintended but direct effect of large-scale biofuel production is the impact on local and regional climate resulting from changes in the energy and moisture balance of the surface upon conversion to biofuel crops. Using the latest version of the WRF modeling system we conducted twenty-four, midsummer, continental-wide, sensitivity experiments by imposing realistic biophysical parameter limits appropriate for bio-energy crops in the Corn Belt of the United States. In the absence of strain/crop-specific parameterizations, a primary goal of this work was to isolate the maximum regional climate impact, for a trio of individual July months, due to land-use change resulting from bio-energy crops and to identify relative importance of each biophysical parameter in terms of its individual effect. Maximum, local changes in 2 m temperature of the order of 1C occur for the full breadth of albedo (ALB), minimum canopy resistance (RC_MIN) and rooting depth (ROOT) specifications, while the regionally (105W-75W and 35N-50N) and monthly averaged response of 2 m temperature was most pronounced for the ALB and RC_MIN experiments, exceeding 0.2C. The full range of the albedo variability associated with biofuel crops may be sufficient to drive regional changes in summertime rainfall. Individual parameter effects on 2 m temperature are additive, highlight the cooling contribution of higher leaf area index (LAI) and ROOT for perennial grasses (e.g., Miscanthus) versus annual crops (e.g., maize), and underscore the necessity of improving location- and vegetation-specific representation of RC_MIN and ALB.

Biofuels from land-rich tropical countries may help displace foreign petroleum imports for many industrialized nations, providing a possible solution to the twin challenges of energy security and climate change. But concern is mounting that crop-based biofuels will increase net greenhouse gas emissions if feedstocks are produced by expanding agricultural lands. Here we quantify the 'carbon payback time' for a range of biofuel crop expansion pathways in the tropics. We use a new, geographically detailed database of crop locations and yields, along with updated vegetation and soil biomass estimates, to provide carbon payback estimates that are more regionally specific than those in previous studies. Using this cropland database, we also estimate carbon payback times under different scenarios of future crop yields, biofuel technologies, and petroleum sources. Under current conditions, the expansion of biofuels into productive tropical ecosystems will always lead to net carbon emissions for decades to centuries, while expanding into degraded or already cultivated land will provide almost immediate carbon savings. Future crop yield improvements and technology advances, coupled with unconventional petroleum supplies, will increase biofuel carbon offsets, but clearing carbon-rich land still requires several decades or more for carbon payback. No foreseeable changes in agricultural or energy technology will be able to achieve meaningful carbon benefits if crop-based biofuels are produced at the expense of tropical forests.

Converting forest lands into bioenergy agriculture could accelerate climate change by emitting carbon stored in forests, while converting food agriculture lands into bioenergy agriculture could threaten food security. Both problems are potentially avoided by using abandoned agriculture lands for bioenergy agriculture. Here we show the global potential for bioenergy on abandoned agriculture lands to be less than 8% of current primary energy demand, based on historical land use data, satellite-derived land cover data, and global ecosystem modeling. The estimated global area of abandoned agriculture is 385-472 million hectares, or 66-110% of the areas reported in previous preliminary assessments. The area-weighted mean production of above-ground biomass is 4.3 tons/ha^-1 /y^-1, in contrast to estimates of up to 10 tons/ha/yr in previous assessments. The energy content of potential biomass grown on 100% of abandoned agriculture lands is less than 10% of primary energy demand for most nations in North America, Europe, and Asia, but it represents many times the energy demand in some African nations where grasslands are relatively productive and current energy demand is low.

» Article in the Stanford Report on Campbell et al. 
» Video by the Stanford News Service.