Wood

Wood is the hard material found in tree trunks, branches and roots. It is made of cells whose walls are reinforced with compounds of cellulose, hemicellulose and lignin — lignin is the substance that binds cells together and provides hardness.

Humans have used wood for thousands of years for fuel, shelter, tools, implements and ships. To the present day it remains one of the most widely used materials in the world, because it is renewable if forests are managed sustainably.

Structure

A tree trunk has layers. The outermost is the bark. Beneath it lies the cambium, a thin layer that produces new cells every year. The light wood visible on the outside is called sapwood, and it carries water and nutrients upward. The innermost core, which is darker in color, is heartwood; it no longer functions in water transport but is harder.

In regions with seasonal climate, annual growth creates visible rings (annual rings). Counting these rings allows the age of a tree to be determined; the science that studies this is called dendrochronology.

Types

The timber industry is divided into two categories: softwood, which comes from coniferous trees such as pine and cypress, and hardwood, which comes from broadleaf trees such as olive, teak and oak. These names do not always reflect actual hardness; some hardwoods are quite soft. Somalia is known for hard woods of the savanna such as qudhac, galool and hagar.

Uses

Wood is used in building houses, furniture, ships and vehicles. When burned and treated chemically it is made into paper and charcoal. A significant portion of the world's population still rely on wood and coal for heating and cooking.

Environment

Uncontrolled deforestation causes soil erosion and reduces carbon stocks. Trees store carbon as they grow, so forest management is part of climate policy. In Somalia, charcoal production and the charcoal trade have been the subject of prolonged debate, with the UN Security Council issuing sanctions related to charcoal exports.