The Land, Always the Land
The relationship between land use and global warming is gaining prominence within climate change policy-making. Oregon is studying how to reduce vehicle miles and thus emissions by reducing urban sprawl [arksearch]. And the biofuel debate rages as food and forests [search] pay a high price from growing and burning plant materials for energy.
It is relatively easy to see how burning fossil fuels causes climate change. What is more inscrutable and often given short thrift is the extent to which the condition of terrestrial ecosystems is coupled to the atmosphere [search]. Humanity is already using nearly half of both the energy captured by plants and the Earth's surface for agriculture. I am certain that a full-accounting of the matter would show millenia of human caused land cover changes to be the primary component of climate change, water scarcity and the global ecological emergency.
To suggest that energy and food can endlessly be produced by intensifying land use ignores very real limits. There exist minimum levels of land that must be maintained in natural, large and intact habitats to power the global ecosystem and biosphere. And agricultural intensification is limited by soil erosion [search], toxic accumulation, failing acquifers and other factors. There is no large body of unused land out there to feed and fuel more people and energy use, and trying to do so dooms the climate, land and Earth.