Biofuels and the "land use cascade"

As readers of Maribo no doubt heard, two papers in last week’s Science addressed the greenhouse gas emissions that arise from clearing lands for biofuel crop production. It is an important subject that has been widely discussed within the scientific community, including my own collection of colleagues, for the past year or two. You might say these papers are the first to “do the math”. The papers conclude what many carbon cycle experts suspect: that any greenhouse gas benefits that come from using biofuels instead of oil are negated when you include the emissions associated with land clearing.

The publication of both papers at once is enlightening because they tackle slightly different, but complimentary, issues.
Fargione et al. address the direct emissions from the land cleared to plant the actual biofuel crops. The examples includes Brazilian Amazon to soybean biodiesel, Brazilian Cerrado to soybean biodiesel, Brazilian Cerrado to sugarcane ethanol, Indonesian or Malaysian lowland tropical rainforest to palm biodiesel, Indonesian or Malaysian peatland tropical rainforest to palm biodiesel, and US Central grassland to corn ethanol.

Searchinger et al. use a global economic model to look more at the indirect emissions. In the developed world, including Canada and the US , forests or grasslands are not being cleared to plant biofuel crops. Instead, biofuels are being produced on land previously devoted to other crops or from grain diverted from another use (i.e. corn grain goes to the ethanol plant rather than the boat shipping it overseas). The change has a cascading effect on the world market. There is less grain available, which can cause other countries to clear land to feed the market.

I like to call problems like that addressed in the Searchinger et al. paper “land use cascades”. There are countless examples -- one of the my favourites is the effect that the surge in soybean production in the US and Brazil in the 90s had on the Yasawa Islands in Fiji (I tell the whole story is here).

These cascades are becoming increasingly important, and increasingly global in scale. For example, the same thinking needs to be applied to forestry-based carbon credit programs. If a segment of BC coastal rainforest slated for logging is protected, does that mean some other forest must be logged to provide the missing pulp and paper? If so, what effect does that have on the net emissions? We may discover that net greenhouse gas savings only occur if we also reduce demand for the products that would otherwise come from that land either cleared (biofuels) or saved (forest carbon credits). More on that later.