Nature
The nature of the GR20
The GR20 is not just an athletic challenge. It crosses one of the wildest territories in the Mediterranean: rare birds of prey, elusive mouflon, high-altitude wetlands, century-old pine forests. Lifting your eyes from the trail means discovering all of this — as long as you walk without harming it.
Wildlife
The bearded vulture, the shadow over the ridges
In Corsican it is called Altore. The Parc describes the bearded vulture as the largest bird of prey in Corsica and in Europe, with a wingspan approaching 2.80 m. This "bone-breaking" vulture feeds almost exclusively on carcasses: it drops bones from a great height onto the rock slabs to reach the marrow inside.
In Corsica it hangs by a thread: only 3 to 4 pairs (down from about ten in 2009), closely monitored by the PNRC under the European Life GYPRESCUE programme (2021-2025: reinforcing the population, securing nests and power lines, raising awareness). Catching sight of its silhouette gliding above a ridge is one of the great moments of the GR20, and a rare privilege.
Wildlife
The Corsican mouflon, elusive and threatened
The muvra (the Corsican mouflon) is a wild sheep endemic to the island and to Sardinia. The The national action plan for the Corsican mouflon (2024) lists two disjunct populations: the Cinto massif in the north (around 600) and Bavella in the south (around 400 to 500), so on the order of 1,000 to 1,100 individuals in total. The species has been protected since 2019.
You mostly come across it at dawn or dusk, on the rocky slopes. Seeing one is never guaranteed: it's a stroke of luck. All the more reason to stay discreet, keep your distance and never leave the trail to "force" the encounter: overcrowding already disturbs these animals.
Wildlife
The Corsican nuthatch, France's only endemic bird
One bird lives only here: the Corsican nuthatch (Sitta whiteheadi) is the only bird endemic to mainland France. It's estimated at around 2,000 pairs, tied to old laricio-pine forests between 1,000 and 1,500 m — exactly the stands the GR20 crosses near Vizzavona and the Vergio pass. Spotted in 1883 by the naturalist John Whitehead, it is still listed as vulnerable: keep an eye (and an ear) out in the tall pines.
Another discreet endemic, this time in the torrents: the Corsican brook newt (euprocte) — an amphibian that breathes through its skin (it has no lungs) and climbs above 2,200 m. Two species you won't meet anywhere else on Earth.
Plant life
The pozzines, a fragile beauty
Around the high-altitude lakes (Lac de Nino is the best-known example) lie the pozzines: high-altitude wet meadows, green and spongy, dotted with small pools of water (from pozzu, the well). It's magnificent, and it makes you want to walk everywhere. Precisely: you mustn't.
These are sensitive habitats. The PNRC asks that you do not trample them, and goes further: at Lac de Nino and on the Cuscionu plateau, the use of trekking poles is banned so as not to puncture these wetlands. Every step off the trail damages them lastingly.
Plant life
From the maquis to the laricio pine
As you climb, you pass through the tiers of Corsican vegetation. Down low, the fragrant maquis (strawberry tree, myrtle, rockrose, heather) up to about 600 m. Higher up, the great forests of laricio pine, the symbol of the GR20, especially around Vizzavona and Bavella: this tree reaches 40 to 50 m and often passes 500 years — the oldest, in the upper Asco valley, approach a thousand years; its straight trunk was once used to make ships' masts.
Above that, the subalpine tier gives way to rock, short grasslands and the pozzines near the lakes and mountain streams. In a few hours of walking, you go from a Mediterranean atmosphere to a high-mountain setting.
Geology
Granite, cirques and rock slabs
The harsh, jagged character of the GR20 is not just an impression. Corsica rests for the most part on an old Hercynian granite bedrock. It is the most mountainous of the large islands of the western Mediterranean, with an average elevation of around 568 m and several massifs exceeding 2,000 m, including Monte Cinto and Monte Rotondo.
On the ground, this granite translates into smooth slabs, boulders, sharp ridges and descents that hammer your joints. The glacial cirques and high-altitude lakes, for their part, are the traces of ancient glaciers — the signature of a mountain range that is younger and rougher than you imagine when you arrive from the beach.
Respect
Walking without harming
The GR20 is beautiful because it is still wild. A few simple habits help keep it that way: stay on the trail (especially on the pozzines), don't swim in the high-altitude lakes, don't feed or disturb the wildlife, carry your waste back down, and know that a drone may not be flown without authorisation. This isn't folklore: it's what keeps the trail alive.
Sources
Where these reference points come from
The whole GR20 lies within the Corsica Regional Natural Park (created in 1972) and skirts mountain Natura 2000 sites such as the Aiguilles de Bavella special protection area and the Renoso massif. The facts above are drawn together from the official sources below; Mon GR20 remains an independent personal site.