E ach year about 10 million hectares of forest is cleared in the tropics, and even larger forest areas may be subject to degradation. Tropical forests may be more than 150 million years old, so each hectare of forest has developed an immense and unique biodiversity that may be larger than that of enormous areas that have developed only since the last Ice Age (e.g., the northern hemisphere). Deforestation is not only a threat to biodiversity and local climate and water regulation, but also to climate change since it leads to large emissions of carbon dioxide (CO
2 ). Ironically, forests are increasing at the expense of agricul-
ture in many high-income countries, such as the United States and Scandinavia, where high salaries and other factors favor this land use (see Chapter 22). This increase (at least partly) compensates for the loss in carbon due to tropical deforestation but does nothing to limit the loss in biodiversity or other local public good services that forests provide, such as climate stability.