A medieval forest didn't need trees, just a king who hunted there
When the Normans brought the word forest to England, it was a legal term for land reserved for royal hunting, whether or not trees grew on it. That confusion survives: there are more than 800 definitions of forest worldwide, and under some of them a patch with no trees at all still qualifies.
The word probably comes from Medieval Latin foresta, first used in Charlemagne's decrees for the king's hunting grounds. Its roots are debated: some trace it to a Late Latin phrase meaning the outer wood, others to a Frankish word related to German Forst and ultimately to an ancient term for coniferous woodland. Romance languages originally used words descended from Latin silva instead, which survives in English sylvan. Magna Carta uses the Norman legal sense, and by the early fourteenth century English writers used forest in its common, legal and archaic meanings alike.
Modern definitions fall into three camps. Administrative ones follow legal designation; land-use ones count cleared timber land as forest; land-cover ones require a threshold of trees. The Food and Agriculture Organization's widely used version demands more than half a hectare, trees over 5 metres and canopy above 10 percent. By that measure, a 2025 assessment found 4.14 billion hectares of forest, about 31 percent of Earth's land, 45 percent of it in the tropics. Austrian law, meanwhile, treats young Norway spruce grown as Christmas trees as farmland.
Forests carry out about three-quarters of the biosphere's gross primary production and hold 80 percent of its plant biomass, estimated in 2025 at 709 gigatonnes. Of their carbon, 46 percent sits in soil and 44 percent in living wood and roots. They also shape the weather. Amazon trees release water ahead of the seasonal rains, starting the wet season two to three months earlier than climate alone would allow, and in regions of moderate rainfall, woodland can flip to savanna once tree cover falls below 40 to 45 percent.
The first forests appeared about 390 million years ago in the Middle Devonian. Later Archaeopteris, part tree and part fern and over 20 metres tall, became the first known plant to cast shade and build soil, and its fallen fronds enriched rivers for early fish. Today most clearance happens in the tropics, driven chiefly by wood, beef, soy and palm oil; over 2,000 years Europe's forest cover fell from 80 to 34 percent.
Source: Forest
