South Korea Geography, Climate & Nature

South Korea occupies the southern half of the Korean peninsula, about 100,000 square kilometres — roughly the size of Iceland or Portugal — with a population above fifty million, which makes it one of the more densely settled countries on earth.

Mountains everywhere

Around seventy per cent of the country is mountainous, and the ranges run down the eastern side, which is why the east coast is steep and the west is flat. Nothing is especially high — the tallest mainland peak, Jirisan, reaches 1,915 metres — but the hills are everywhere, including inside Seoul, where Bukhansan national park is reachable by subway and rises above eight hundred metres.

Two very different coasts

The east coast on the Sea of Japan is deep, with a narrow shelf, few islands and long sand beaches. The west coast on the Yellow Sea has one of the largest tidal ranges in the world — up to nine metres — exposing vast mudflats twice a day. Those getbol tidal flats were UNESCO-listed in 2021 and are a critical stopover for migratory shorebirds on the East Asian flyway.

Islands

There are more than three thousand, most of them off the south and west coasts. Jeju, off the southern tip, is the largest and is entirely volcanic — a shield volcano with a crater lake at 1,947 metres, lava tubes among the longest in the world, and its own UNESCO listing.

Rivers and cities

The Han flows through Seoul, the Nakdong through Busan, and both are heavily engineered. Population is concentrated in the north-west: roughly half the country lives in the Seoul metropolitan area alone.

The border

The Demilitarised Zone, four kilometres wide and 250 long, has been effectively closed to people since 1953, which has made it an accidental nature reserve holding species that are rare or gone elsewhere on the peninsula.

South Korea has a temperate monsoon climate with four seasons that are distinct enough to organise the national calendar around, and a wide gap between the extremes.

Winter

December to February is cold and dry, with Seoul averaging highs near freezing and a continental wind off Siberia that makes it feel colder. Snow falls but rarely lies long in the capital; Gangwon province in the east gets a great deal and has the ski resorts. The south and Jeju are noticeably milder.

Spring

March to May is mild and increasingly clear, with cherry blossom moving north from Jeju in late March to Seoul in early April. It is also the season for yellow dust blown in from the deserts of Mongolia and northern China, which combines with local pollution to push air quality readings high — masks are widely worn and the daily forecast is checked.

Summer

June to August is hot and very humid. The jangma monsoon front sits over the peninsula from late June into July and delivers the majority of the annual rainfall in a few weeks, often in torrential bursts. August adds heat above 33°C with humidity that makes the cities uncomfortable, and typhoons arrive between July and September, usually striking the south first.

Autumn

September to November is the reward: dry, stable, clear skies, comfortable temperatures and maple colour moving south through October. Most Koreans will tell you it is the best season, and they are right.

Regional differences

The east coast is warmer in winter than the interior thanks to the sea; the south-west is wetter; and Jeju is subtropical enough to grow citrus and palms.

South Korea is small, mountainous and densely populated, and its biodiversity has to be read against that. Around seventy per cent of the country is mountainous, the ranges run down the eastern side, and nothing is especially high — the tallest mainland peak, Jirisan, reaches 1,915 metres — but the hills are everywhere, including inside Seoul, where Bukhansan national park rises above eight hundred metres and is reachable by subway. That accessibility is the country's distinctive conservation fact: protected mountain forest is a commuter destination here rather than an expedition.

The two coasts are entirely different systems. The east coast on the East Sea is deep, with a narrow shelf, few islands and long sand beaches. The west coast on the Yellow Sea has one of the largest tidal ranges in the world — up to nine metres — which exposes vast intertidal mudflats twice a day. Those flats are the ecologically important part: they are a critical staging ground on the East Asian-Australasian flyway, and the birds that use them have nowhere else comparable between Siberia and Australia.

Jeju is the third system, volcanic and subtropical, with its own flora, lava tubes and a climate closer to southern Japan than to the mainland. It is the only part of the country where the vegetation is not broadly temperate.

And then there is the accidental one. The demilitarised zone is four kilometres wide and runs the width of the peninsula, and it has been almost entirely free of human activity since 1953 — which has made a war zone into one of the best-preserved temperate habitats in Asia by doing nothing at all.

Korean wildlife is a story of loss and slow, deliberate return. Large mammals were largely cleared from the peninsula during the Japanese colonial period and the Korean War; the Amur leopard and the tiger are gone from the South, and the Asiatic black bear survives in very small numbers under a reintroduction programme in Jirisan.

What South Korea does have in internationally significant numbers is birds, and the reason is the Yellow Sea. The west-coast mudflats, exposed by tidal ranges of up to nine metres, are a critical refuelling stop on the East Asian-Australasian flyway for shorebirds moving between Siberian breeding grounds and Australian wintering grounds. Reclamation has destroyed a great deal of that habitat, which is why what remains matters disproportionately.

The cranes are the emblem and they winter in the strangest possible place: the demilitarised zone and the civilian control line behind it, where the absence of farming, building and people since 1953 has produced habitat that exists nowhere else on the peninsula. Birdwatchers go to the DMZ area in winter for exactly this reason, and it is the clearest example anywhere of conservation by accident.

Practically: this is a birding and hill-walking country rather than a large-mammal one. Bukhansan from a Seoul subway station, Jirisan for the high ridges, the west-coast flats at migration, and the DMZ area in winter are the four things worth planning around.