Introduction

Markets have altered the global forest landscape to create cropland and pasture. Of the original 5 billion hectares of forest in 1850 (see Chapter 3), the forest has shrunk to 3.6 billion hectares today (Food and Agricultural Organization of the United Nations [FAO] 2010a). A great deal of this conversion was to cropland (Ramunkutty and Foley 1999). At the same time, the forestry sector harvested most of the world's primary forests, replacing it with younger secondary forests (Berck and Bentley 1997). Both of these market activities led to substantial carbon (C) emissions to the atmosphere by reducing the amount of C stored in global primary forests (see Chapter 3).

In addition to these historic activities, several authors claim that market activities continue to lead to substantial C emissions to the atmosphere. The Intergovernmental Panel on Climate Change (IPCC) argues that land use is still responsible for 20 percent of carbon dioxide (CO2) emissions. In the 1990s alone, deforestation contributed 5.8 Gt CO2e (gigaton carbon dioxide equivalent) (IPCC 2007a). The remaining 80 percent of emissions came largely from burning fossil fuels. In addition, agriculture was responsible for methane emissions equal to 3.3 Gt CO2·yr−1 and nitrogen dioxide emissions equal to 2.8 Gt CO2·yr−1 (IPCC 2007b). Although we will not examine these other gases, they do contribute to climate change (IPCC 2007a).