According to the Energy Information Administration, CO emissions in the USA in 2007 were 6.0218 billion metric tons (Gt). Calculate the land area that needs to be planted with trees to sequester this emission. Ohio forests sequester carbon at a rate of 130 metric tons/hectare per 100 years. This corresponds to 400 trees/hectare. How does this area compare with the area of the USA? What does this say about the sustainability of US CO emissions?