In Yunnan the Yangtze, the Mekong and the Salween run parallel inside the same band of mountain
Three of Asia's great rivers run side by side for more than three hundred kilometres, separated by ridges over 6,000 metres high. The province runs from the 76 metres of the Red River valley to the 6,740 of Kawagarbo, and that difference explains why almost everything grows here.
There is a geographical fact in the north-west of this province that is hard to picture even on a second reading: three of Asia's most important rivers run side by side, in the same direction, for more than three hundred kilometres.
One of them will end at Shanghai. Another in the delta of southern Vietnam. The third in the Andaman Sea. Here, though, they are a few dozen kilometres from one another, separated only by walls of mountain.
01 Six thousand six hundred metres of range
Before the rivers it is worth looking at the vertical scale, because that is what orders everything else. Yunnan's lowest point is 76.4 metres above sea level, in the Red River valley, near the Vietnamese border.
The highest is Kawagarbo, at 6,740 metres, in the far north-west. Between the two there are 6,664 metres of difference inside one province, and with them the whole climatic range that fits between the humid tropics and permanent snow.
In area, Yunnan covers 394,000 square kilometres, more than Germany and Italy combined, and it holds a population of 47.2 million. It is not a mountain district: it is a whole country stood on its edge.
02 Three rivers inside the same band
The three rivers are the Jinsha, which is the upper Yangtze; the Lancang, which is the upper Mekong; and the Nu, which is the upper Salween. They are separated by the Hengduan mountains, ridges whose peaks pass 6,000 metres.
The whole area has been a World Heritage Site since 2003, with an extension in 2010. It is fifteen core areas totalling 939,441.4 hectares, plus 758,977.8 of buffer zone, inside a rectangle of roughly 180 by 310 kilometres.
The cause of that improbable arrangement is tectonic: the area sits at a collision point of plates, and the resulting folding raised parallel ridges that forced the three rivers to wedge themselves between them rather than spread across the territory.
The practical consequence for a traveller is that going from one river to the next is not crossing a plain: it is climbing a ridge and coming down again. Distances on the map mislead here more than almost anywhere.
03 Why this produces so many species
A territory with six thousand metres of vertical range and parallel valleys isolated from one another works as a biodiversity factory. Each altitude has its climate, each valley is cut off from its neighbour by a barrier, and species diverge.
The numbers bear it out. Yunnan holds around 17,000 vascular plant species, 2,500 of which grow nowhere else. It shelters 42.6% of all the country's protected plant species and 72.5% of its protected wild animals.
The rivers do the same: around 620 freshwater fish species, almost 40% of all those in China. And within the protected area of the three rivers there are some 6,000 plant species, 173 mammals — 81 of them found nowhere else — and 417 birds, 22 of them endemic.
Unesco sums the whole up with a phrase worth keeping: it may be the most biologically diverse temperate region on Earth. Not in Asia: on Earth.
04 The tropical south
At the opposite end of the province the landscape looks nothing like it. In the south, towards the border with Laos and Myanmar, the Mekong is already wide and low, and the climate is humid tropical.
That low strip produces much of what Yunnan sends to the rest of the country and the world: tea, coffee, flowers and tobacco. The province is agricultural to a degree its reputation as a mountain destination tends to hide.
It also explains the lowest point on the map. The 76.4 metres of the Red River valley are less than a thousand kilometres in a straight line from a summit of 6,740. Few places in the world put those two figures inside the same administrative unit.
05 The steps in between
Between those two extremes lies most of the territory, and it works in storeys. Kunming, the capital, sits at 1,888 metres; the north-western towns climb from there until they pass three thousand.
That stepping has an agricultural consequence visible from the road: terraces. Where there is no flat ground, it gets manufactured. Those of Yuanyang county, in the south, cover entire hillsides and work as a gravity irrigation system from top to bottom.
And it has another climatic consequence that surprises arrivals. At 1,888 metres and at this latitude, Kunming has a subtropical highland climate with mild temperatures in all twelve months. Being in the subtropics does not mean being hot here.
06 How to travel a province like this
The first decision is accepting that it does not fit whole. With 394,000 square kilometres and six thousand metres of vertical range, Yunnan is not done in one trip, just as Germany and Italy are not done in one trip.
The second is choosing an axis and following it. The most logical is the vertical one: climbing from Kunming towards the north-west gaining height gradually, which is also the sensible way to get used to three thousand metres. The alternative is dropping to the tropical south and staying there.
And the third is reading the map differently. In Yunnan what separates two places is not the kilometres, it is the ridges in between. Grasp that — that geography here is measured from the bottom up rather than side to side — and the province stops being a catalogue of names and becomes one understandable thing.
