French Guiana Geography, Climate & Nature

French Guiana lies on the north-east coast of South America between two and five degrees north, an outermost region of the European Union bounded by the Maroni River and its tributaries on the Suriname side, the Oyapock and the Tumuc-Humac mountains on the Brazilian side, and 320 kilometres of Atlantic coast. Its land area is about 83,500 square kilometres, and it extends almost 400 kilometres inland in two natural zones: the Terres Basses, a low swampy coastal strip 16 to 48 kilometres wide, and the Terres Hautes, a granite peneplain of the 1.7-billion-year-old Guiana Shield worn into steps of low steep hills, with the highest point at Bellevue de l'Inini, 851 metres. Almost the entire territory is rainforest -- 98.9 per cent forest cover -- and its many large rivers, their courses broken by rapids, are the only natural way into the interior; the Maroni system runs 612 kilometres, the Oyapock 403. The soils are among the poorest in the world.

The people live on the coast. Cayenne, the capital, had 62,675 in the commune and 153,884 in its metropolitan area in 2023, about half the territory's 293,996; Saint-Laurent-du-Maroni, 268 kilometres west, had 54,429; Kourou, 64 kilometres from the capital at the mouth of its river, 24,824. The Salvation Islands lie 11 kilometres off the coast and 14 north of Kourou. Inland, the Guiana Amazonian Park covers 41 per cent of the territory on the communes of Camopi, Maripasoula, Papaïchton, Saint-Élie and Saül, reached by air or river.

The road network is about 2,200 kilometres, concentrated on the coast: the N1 from Cayenne to Saint-Laurent through Kourou and Sinnamary, the N2 from Cayenne to Saint-Georges and the Oyapock bridge into Brazil. Félix Éboué airport is at Matoury, 16 kilometres from the capital.

French Guiana lies within six degrees of the Equator and rises only to modest heights, so temperatures and humidity are high all year: Cayenne's highs average about 30 degrees and its lows about 23 in every month, and the tourism committee gives an annual mean around 26 with minimums always above 20 and peaks to 33, tempered by the trade winds on the coast. Rain is governed by the Intertropical Convergence Zone and its thunderstorms: from December to July it is heavy everywhere, typically more than 330 millimetres a month, with a small rainy season in January and February, a brief sunny petit été de mars, and the main rains in May and June. From August to November the eastern half has a warm dry season with under 100 millimetres a month and highs above 30 in September and October, the sunniest months; Saint-Laurent-du-Maroni in the west stays wetter, a tropical rainforest climate rather than the east's tropical monsoon one.

The territory is sheltered from cyclones, though the UK advisory notes a risk of tropical storms in the December-to-July rainy season, and the Canadian advisory that seasonal flooding from mid-December to June can cut roads with mudflows and landslides and that bush and forest fires occur. Mosquitoes are most active in the rainy months; malaria exists in certain areas and seasons, dengue and Zika throughout, and yellow-fever vaccination is compulsory.

Best Destinations by Month has the practical reading.

French Guiana is the most forested territory in the European Union and one of the most biodiverse on earth: 98.9 per cent forest, much of it primary, across tropical rainforest, coastal mangroves, savannahs, inselbergs and many kinds of wetland, in three ecoregions -- the Guayanan Highlands moist forests, the Guianan moist forests and the Guianan mangroves. The Guiana Amazonian Park, France's and the EU's largest national park, created in 2007 over 20,300 square kilometres of core and 13,600 of buffer, records 90 species of amphibians, 133 reptiles, 520 birds, 182 mammals including many bats, and more than 200 freshwater fish; with Brazil's Tumucumaque it is the largest rainforest protected area in the world. On the Kaw mountain the Trésor regional reserve holds the Guianan cock-of-the-rock, the male bright orange, and the Kaw marshes below hold the caimans the tourism committee sends visitors to see at dusk.

The coast is the turtles': the Amana reserve, 14,800 hectares since 1998 across Awala-Yalimapo and Mana, protects one of the world's largest leatherback nesting sites, with 5,029 to 63,294 nests a year counted between 1967 and 2005; the females lay 80 to 90 eggs between March and July and the hatchlings emerge two months later, and green, olive ridley and occasionally hawksbill turtles nest beside them. The threat is inland: illegal gold mining in the remote interior, ecologically destructive and chronic.

No fuller species inventory was consulted beyond the sources named in the data file.

The animals a visitor can reasonably expect are the caimans of the Kaw marshes on an evening boat, the leatherbacks of Plage des Hattes on a March-to-July night, the cock-of-the-rock at its lek on the Kaw mountain with a guide, monkeys and macaws from a pirogue on the Maroni or in the park communes, and the bats -- many species -- at dusk anywhere. The jaguar, tapir and giant otter of the park's inventory are for the patient and the guided; nothing here is promised by the sources beyond the counts above.

The practical zoology is the advisories': mosquitoes carrying dengue, Zika and in places malaria, rabies possible in wildlife including bats, and rivers that are the only road inland and carry their own risks.