In the Western Cape one mountain holds more plant species than the whole United Kingdom, and the cause is that the soil is terrible

One figure gets repeated so often in the Western Cape that it starts to sound like a brochure, and yet it is literal: Table Mountain National Park, 221 square kilometres, grows more plant species — over two thousand — than the whole of the United Kingdom. Not a British region: the entire country.

The interesting part is not the figure. It is the reason, which runs exactly counter to what you would expect.

01 A floral kingdom the size of a small country

Botanists divide the world into six great floral kingdoms. Five of them are enormous: they span whole continents. The sixth occupies 78,555 square kilometres at the southwestern tip of Africa, an area comparable to Austria or Ireland, and it is the only one that fits almost entirely inside a single country.

The contrast is uncomfortable to take in. This kingdom accounts for less than 0.5% of Africa's land area and concentrates around 20% of all its plant diversity. It holds five of South Africa's twelve endemic plant families and 160 genera that exist nowhere else. Of its more than nine thousand species, two in three do not grow naturally outside it.

The vegetation has its own name: fynbos, Afrikaans for fine bush. Hard, small-leaved shrubs, heaths, reed-like restios and proteas. From a distance it looks like ordinary Mediterranean scrub. Up close it is something else.

02 Two thousand species in 221 square kilometres

The extreme concentration shows best in the small case. Table Mountain National Park covers 221 square kilometres across the Cape Peninsula and contains more than two thousand plant species. That is a smaller area than many metropolitan regions, and it beats a country of 240,000 square kilometres for botanical variety.

The flip side of that richness is fragility. The Table Mountain range has the highest concentration of threatened species of any continental area of equivalent size in the world. When a plant only grows on one mountainside, building on that mountainside is enough.

03 Bad soil as the engine

Here comes the counterintuitive part. Fynbos grows on acid sands and desperately poor soils derived from Table Mountain sandstone: virtually no nutrients, no water retention and no accumulated organic matter. Under conditions like that, no plant can grow fast and smother the rest.

In fertile soil, two or three vigorous species take the light and the rest disappear: that is why a temperate European forest has few dominant species and a great deal of biomass. In poor soil there are no clear winners. Each species specialises in a minuscule niche — an aspect, a degree of acidity, a depth of sand — and barely competes with its neighbour.

Add the relief to that. The Cape Fold Belt is a set of nearly parallel folded sandstone ranges reaching 2,325 metres, which chop the province into valleys with different aspects, rainfall and soils. Each valley is an isolated laboratory; each isolation manufactures endemics. It is the same arithmetic as any archipelago, done with mountains.

04 A landscape that needs to burn

One ingredient is missing, and it is the one that most disconcerts visitors: fire. Fynbos is a fire-prone shrubland, and not by accident. Many of its plants depend on fire to reproduce: they hold their seed in woody cones that only open with heat, or they need smoke to germinate.

The natural interval most often cited runs between ten and twenty years. Burning too often exhausts plants that have not yet set seed; never burning lets a few tall shrubs smother everything else. The balance is narrow, and managing the park largely means managing it.

For anyone arriving from outside, this demands a mental adjustment. A black, scorched hillside in the Western Cape is not necessarily a disaster: in many cases it is the first step of a cycle, and by the following winter that same slope flowers more than any other.

05 Two oceans, twelve degrees apart

The other physical feature that orders the province is in the water. Up the western coast runs the Benguela current, cold and driven by deep-water upwelling; down the eastern coast comes the warm Agulhas. The two meet at the southern tip of the continent, and the effect is measurable on any beach.

On Cape Town's Atlantic seaboard the sea can sit at 10 degrees, with an annual average of 13. In False Bay, on the other side of the same peninsula and less than twenty kilometres away by road, the annual average is 17 and in summer it passes 22. Swimming on one side or the other are two different experiences on the same day.

That asymmetry also explains the climate. The Western Cape is the only part of Africa with a genuine Mediterranean climate: cool wet winters, hot dry summers. Cape Town receives 492.8 millimetres a year, of which 92.3 fall in June and barely 9.4 in January. It is the inverse of the rest of South Africa, where the rain comes in summer.

06 What this changes for the traveller

The first consequence is that you have to change the scale you look at. In the Western Cape the spectacle is not the large animal crossing the horizon, but the square metre in front of you. A slope that looks like dry scrub from the car contains, if you crouch, a dozen species that exist nowhere else on the planet.

The second is that the calendar matters more than usual. With winter rain and summer drought, the landscape is green and flowering between August and October, and brown and dusty in January and February. It is the opposite of the rest of the country, and anyone combining both zones in one trip has to choose which to sacrifice.

The third is about expectation. This is the corner of Africa that least resembles the idea of Africa people bring with them: no malaria, a Mediterranean climate, two oceans at incompatible temperatures and a shrubland that has to be burned to stay alive. It is a place better understood with a magnifying glass than with binoculars.