One of the issues related to biofuels is the magnitude of greenhouse (GHG) emissions that may arise from direct use or indirect-land use for bioenergy production. Direct land-use emissions are "generated from land committed solely to bioenergy production", while indirect land-use emissions "occur when biofuels production on cropland or pasture displaces agricultural activity to another location, causing additional land-use changes and a net increase in carbon loss". An international team of scientists from the United States, Brazil and China, examined these GHG emissions from direct and indirect effects of possible land-use change scenarios from an expanded 21st century global cellulosic bioenergy program. Using linked economic and terrestrial biogeochemistry models, the study found that (1) large greenhouse gas emissions from indirect land-use changes are "unintended consequences of a global biofuels program", and these consequences (specially if these involve clearing of forests) will actually "add to the climate-change problem rather than helping to solve it, (2) additional fertilizer that will be required to grow biofuel crops in the future will result in nitrous oxide (another type of greenhouse gas) emissions that will surpass carbon dioxide, in terms of warming potential, (3) "a global greenhouse gas emissions policy that protects forests and encourages best practices for nitrogen fertilizer use can dramatically reduce emissions associated with biofuels production". The complete study is published in an October issue of the journal, Science (URL above)..