The German Advisory Council on Global Change (WBGU) performed a study on the conservation of the biosphere [17]. One of the conclusions of this work was that between 10 and 20 % of the world land mass should be protected to preserve the different functions of the biosphere, such as climate regulation, and its biodiversity.

Recent statistics provided by the World Database on Protected Areas state that 14% of the land mass is currently protected [18].

Therefore, to be at the upper limit of the range put forward by the WBGU, an additional 6% of the global land mass should be protected. Although it is not known where this 6% is located, we assume in our cal­culations that meeting this requirement will also reduce the land potential for rain-fed cultivation of energy crops by 6%. The reduction then totals

540,0 km2 (54 million hectares). This reduction is additional to the ex­clusion of currently protected land based on the IIASA study.