This is called the carbon fertilisation effect. As a consequence of carbon fertilisation, water use efficiency may also increase. Increase in growth rates however, would vary enormously within ecosystems and between species. In general, it is expected that the negative impacts of climate change on forests will have a greater impact than any positive effect due to an increase in growth rates as a result of elevated atmospheric carbon dioxide concentrations. As well as the effects on forests themselves, climate change is expected to influence societies and economies dependent upon forestry.
Forest products make up the third most valuable international commodity after oil and gas.
Trade is expected to increase in the 21 st century along with demand, particularly in the developing countries. Global warming may well affect the development of such developing economies, particularly if current rates of deforestation remain unchecked and the unsustainable management of forests continues. As a consequence, societies dependent upon the income, food and shelter their forests provide them may well face increasing stresses due to crop failures , soil nutrient depletion and the effects of extreme weather events in the years to come.