What do the Amazon Jungle and London have in common?

Forestry

by Sarah Simonovich March 13, 2018

Twice the size of India, the Amazon rainforest in South America is the single largest tropical rainforest in the world. Unrivaled in scale and biodiversity, it’s home to endemic and endangered flora and fauna.

South America's Amazon is the largest rainforest in the world.

London, on the other hand, is one of the most iconic cities in the world and the most populous city in the UK. While it is also diverse (albeit in a different way), London shares another commonality with the Amazon: they’re both forests. According to the United Nation’s definition, anyway. London’s more than 8 million trees—almost one per person—make it a green city in more ways than one.

London, one of the most populated places in the world, is technically considered forestland.

London probably isn’t the first place that comes to mind when you think of forestland. Germany’s Black Forest or California’s Sequoia National Park are likely higher on your list. So how can London be a forest?

What makes a forest

Forests can actually be surprisingly difficult to define—there are literally hundreds of definitions. All stress the importance of trees in the system and tree cover to varying degrees. However, there is agreement in size: all “forests” need to be at least one acre. Greater London is 1,572 km2 (607 square miles), which definitely fits in the criteria for size.

Besides area, though, a forest needs trees. Calling land forestland (versus the much smaller woods, for example) also depends on tree coverage. This ranges from 5% to 100%. The U.S. National Vegetation Classification system considers forests as having anywhere from 60% to 100% tree cover while the USDA Forest Service requires, at minimum, 10% cover.

For a more global definition, the Food and Agricultural Organization (FAO) of the UN defines a forest as “Land with tree crown cover (or equivalent stocking level) of more than 10 percent and area of more than 0.5 hectares (ha). The trees should be able to reach a minimum height of 5 meters (m) at maturity in situ.” By this definition, both the Amazon Jungle and London can both be classified as forests.

Even if you say that yes, London is a forest, here’s what it’s not: timberland.

All timberland is forestland, but not all forestland is timberland

While part of determining a forest is related to the number of trees, not all of those are available for use as commercial products. That distinguishes timberland from general forests (and London). Timberland is a forest capable of producing at least 20 cubic feet (0.6 cubic meters) of industrial wood crops per acre (0.4 hectares) of land per year.

While London produces an impressive GDP, it could not sustain this particular industry. And sustainability plays a part in defining timberland: commercial lands can be used repeatedly so long as the net annual gain remains positive. Net annual growth refers to the average annual net increase in tree volume during an established period. Components to determining net annual growth include the increment in net volume of trees at the beginning of the year surviving to its end, plus the net volume of trees reaching the minimum size class during the year, minus the volume of trees that died during the year, and minus the net volume of trees that became cull trees during the year.