Trees are seen as a valuable economic asset but only once they have been cut down for their timber. Our economic system in fact values dead trees as being assets, not live ones. In its way, the plight of the world's forests and the attempts to manage and preserve them is indicative of the whole reappraisal of the "meta economics" that is demanded by the need to fight climate change and reclaim a safe climate.
Trees cover about 30% of the Earth's total land area, but the forests are unevenly distributed around the world, with just 10 countries possessing two thirds of the total, whilst 64 countries have less than 10% of their land area as forest cover. Just over a third of the world's forests are truly wild places with no clearly visible indications of human activity. Only 4% are forest plantations, growing trees to order mostly for the paper industry. The remainder of the world's forests are a somewhat haphazard alliance between people and plants, supporting the livelihood of an estimated 1.6 billion people. Some of them mange to do this sustainably, but an awful lot do not.
Generally speaking, the richest biodiversity, measured in terms of the variety of plants, birds and other species in any given place, is to be found in the wild forests that are remote from humans.
Broadly speaking, the world's forests grow in two great lateral bands, one stretching across northern latitudes and incorporating the forests of North America, Scandinavia and Russia. This band is of the type of forest known as 'temperate and boreal'. These contain the type of trees that are most familiar to people in Britain, with a mix of broadleaf trees such as oak, ash, sycamore and chestnut along with evergreen and needle leaf varieties such as pine, spruce and larch. The other major band runs across latitudes in the southern hemisphere and incorporates the forests of South America, Central Africa and Asia. These are tropical forests and are not all rainforests, as some of them are at higher altitudes or by the coast where they form mangrove forests. Mangroves are particularly important. They are tidal forests and have important functions as natural sea defenses, breeding grounds for fish, and habitats for lots of other species.
The probability of sea-level rises and extreme weather events caused by climate change raises the importance of mangroves as a buffer protecting coastlines in the tropics and subtropics. Despite this, mangroves worldwide have been subjected to an appalling rate of destruction resulting from over-harvesting for timber and fuel wood, clearing for shrimp farms, agriculture, coastal development and tourism. Mangroves have been destroyed much faster than any other forest type.
Forest exploitation, just like fossil fuel exploitation, occurs in line with the same economic system that pays no price for the cost of environmental destruction. Indeed, destroying forests for timber is big business, with the global value of wood imports worth $160 billion in 2006 and the rate of cutting them down outstrips the rate of replanting by about 7m hectares a year (which is the space occupied by around 85 billion trees).
Although forests have lots of different possible uses, policymakers, particularly in the developing world, often do not consider forest to have a value other than timber, and defend their exploitation on the basis that the developed world destroyed their forests years ago as part of the development process. Besides timber, forests can also produce other direct use products such as latex, cork, fruit, nuts, spices, natural oils and resins, and medicines. Many of the medicines we use today have come from forest products and nobody knows what else may be discovered.
Forests can also be used for recreation and even spiritual respite. As these uses are related to the existence of a range of tree, plant, animal and other species, forests have an important role in providing habitat for the preservation of these species, particularly in tropical areas. In fact, tropical rainforests contain a phenomenal range of species, more than twice as many as any other forest type and many more of them are unique to their own forest. Forests also have important benefits for the countries in which they are located in terms of recycling nutrients in the soil and providing watershed protection. Forested watersheds act like a sponge that slowly lets out the water so providing a more constant water flow into the rivers and so reducing floods. Cutting down the forests also leads to the soil being washed away, taking its nutrients with it and leading to build ups of mud in water reservoirs and rivers. What's more, forests have a big impact on climate both locally and on a wider scale. Local rainfall can be reduced once a forest has been cut down because the sponge dries out and the trees are no longer giving out water vapor.
Lastly, of course, once you have cut down a tree and turned it into timber, it is no longer breathing and removing carbon dioxide from the atmosphere. And that is a big contributor to the global greenhouse gas problem. Not only have we been putting pressure on the atmospheric system by pumping out extraneous gases from industrial, transport and farming activities, we have been cutting down the lungs of the planet at an alarming rate. So much so that around a fifth of the GHG problem is due to deforestation.