Measuring progress of Forests: Density or Volume make more sense than strictly Areal data

On the UN  International Year of Forests, here is an article reminding that Forests should not only be measured in terms of area but also in density or volume. Forests surfaces might have shrunk globaly but those that have been maintained are now more dense than before. This is partially because of better forestry management which also makes them more performant in storing carbon.

This again emphasizes the importance of promoting appropriate biodiversity management measures, while the extensive planting of single tree species cannot be a sufficient response in climate change mitigation/adaptation policies:

"A National and International Analysis of Changing Forest Density"

by the University of Helsinki Faculty of Bioscience, The New York Rockefeller University and the Department of Forestry and Horticulture - Connecticut Experimental Agricultural Station

Aapo Rautiainen, Iddo Wernick, Paul E. Waggoner, Jesse H. Ausubel, Pekka E. Kauppi

Abstract

"Like cities, forests grow by spreading out or by growing denser. Both inventories taken steadily by a single nation and other inventories gathered recently from many nations by the United Nations confirm the asynchronous effects of changing area and of density or volume per hectare. United States forests spread little after 1953, while growing density per hectare increased national volume and thus sequestered carbon. The 2010 United Nations appraisal of global forests during the briefer span of two decades after 1990 reveals a similar pattern: A slowing decline of area with growing volume means growing density in 68 nations encompassing 72% of reported global forest land and 68% of reported global carbon mass. To summarize, the nations were placed in 5 regions named for continents. During 1990–2010 national density grew unevenly, but nevertheless grew in all regions. Growing density was responsible for substantially increasing sequestered carbon in the European and North American regions, despite smaller changes in area. Density nudged upward in the African and South American regions as area loss outstripped the loss of carbon. For the Asian region, density grew in the first decade and fell slightly in the second as forest area expanded. The different courses of area and density disqualify area as a proxy for volume and carbon. Applying forestry methods traditionally used to measure timber volumes still offers a necessary route to measuring carbon stocks. With little expansion of forest area, managing for timber growth and density offered a way to increase carbon stocks."

Clic here for full article

Other known forests facts are that:

• Forests cover about 31 per cent of the land on Earth, around 4 billion hectares, and contain more than two-thirds of the world’s terrestrial species. The Amazon basin alone is home to an estimated 25 per cent of all land-based species.
• 53 per cent of the world’s forests are found in just five countries: Brazil, China, Canada, the Russian Federation, and the United States of America.
• More than 1.6 billion people depend on forests for their livelihoods; forests are home to an estimated 300 million people around the world.
• 80 per cent of people in developing countries rely on traditional medicines, up to half of which originate from plants found mainly in tropical forests.
• Forest biodiversity is the basis for more than 5,000 commercial products, from aromatic oil distilled from leaves to herbal medicines, food and clothing. 
• Finally they provide clean water; they inspire us in art, research and religion; and they are essential to the survival and well-being of people everywhere—all 7 billion of us.