By Hervé CUBIZOLLE, Francis MULLER and Mariette MAYINDZA MOUANDZA, * EVS-ISTHME UMR 5600 CNRS, St-Etienne, France

** Pôle-relais tourbières, Fédération des Conservatoires d'espaces naturels, France

Photographs by the authors.

Mires in French Guiana: between knowledge and prospective

What is the purpose?In a short mission led in 2011,

we intended to confirm the presence of peatlands in different parts along the coast of French Guiana and see in what conditions they were.

We wanted also, with the valuable help of local naturalists and using the different maps already available, to precise the location and surface occupied by peat soils in this territory.

Bogota

How to consider mires in Guiana?• Mires are often not considered as one of the local ecosystems, as the vegetation of

peat soils has not been characterized : it can be mangroves and other types of forests, savannahs, …

• The word ‘tourbières’ (mires) is not used locally and the local term ‘pégasse’ (for peat or something similar) may be ambiguous

• Their vegetation is not well defined: soil/ plants link

The pedologic coring area at the heart of the Euterpe oleracea station at Pointe Maripa

Moucou-moucou (Montrichardia

arborescens, Araceae), common in peat-rich

soils in Kaw.

Savannah with Eleocharis sp. at the southern end of the Pripris de Yiyi protected area.

An attractive but difficult territory• What can be the part of France in

increasing knowledge and protection of equatorial peatlands, at a moment when Guiana shows:– some positive aspects: ¤ creation of a National Park

occupying the Southern fourth of the territory (20,281 km2 for the core area, the largest of the European Union),

¤ existence of large nature reserves, like Amana and Kaw (947 km2 of protected swamps for the latter)…

Guiana : 86,500 km2, 230,000 inhabitants, about 95% of equatorial forests, some large wetlands along the coast

– and sadder ones : ¤ illicit gold mining, with 2

gendarmes recently killed by traffickers;

¤ off-shore oil research.

Litterature about local mires

• Concerning the thickness of the layers, they could be highly variable, but would reach 9 metres in some areas, which are not defined nor named.

• No scientific publication describing peat coring has ever been found, therefore it seemed indispensable to go into the field and collect complementary information.

• Several authors gave a surface of 1,620 km2 of peatlands in French Guiana, without any further precision, or corresponding to coastal marshes. The prevailing feeling is that each publication borrowed data from older ones. Maps include the whole littoral, which is widely occupied by mangroves, growing on specific soils like thiosols or sulfatosols, even if intercalated peat layers can be found.

Peat in a private fish pond in construction near Mana, NW Guiana

Prospections sur le terrain: 6 secteurs visités en novembre 2011

Région de Mana et

Réserve naturelle nationale d’Amana

Réserve naturelle nationale

des Pripris de Yiyi

Réserve naturelle nationale

des Marais de Kaw

Mangrove de Kourou

Savane humide du Galion

Pinotière de la Pointe Maripa

Four others were explored in the Cayenne/Kourou region: - hydromorphic depressions in the heart of the primary forest of Pointe Maripa, - mangroves of Kourou - wet savannahs of Galion and of Pripris de Yiyi. 3 places, mapped as peatlands by pedologists, could not be reached during the mission: the area of Régina, the Island of Cayenne, the eastern part of the Amana NNR.

We prospected with a pedologic corer in six sectors.

Two sectors showed some peat surfaces: -the marshes of Kaw, in the East

- the rice plantation areas of Mana, in the West.

Mires in the marshes of Kaw• The prospected area is located in the National Natural Reserve of Kaw-Roura, about

20 km from the village of Kaw, between Cayenne and Régina. The altitude is ca. 2m a.s.l.

• In this area, the plain of the river Kaw, completely flooded during the rainy season, is from 1 to 2 km wide. The width of the river itself does not exceed 30 m

Along river KawCrossing an open sedges area in search of peat patches, Kaw marshes, Régina [973]

Mires in the marshes of Kaw

In our soil coring, made in a wood of the floodplain, the thickness of peat does not exceed 85 cm,.The following stratigraphy was observed: -from 0 to -3 cm, an abundant litter, mainly composed of leaves - from -3 to -40 cm, a fibrous to mesic peat, showing fragments of wood and living roots - from -40 to -85 cm, a similar facies, but colour is lighter and getting closer to grey- from -85 to -125 cm, sticky clay, very homogenous, gley level

The gley level.

View of the cored area, near river Kaw,

Régina [973].

The upper peat level.

Peatlands in the Mana area• The second area that we prospected was located on the western part of Guiana, near

Mana. Peat had been mapped by pedologists in two places. • Unfortunately, all of the area to the north of the Mana - Crique Jacques road has been

deeply perturbed by the development of rice cultivation since the middle of the 1970’s , most of these fields being now abandoned!

Area disturbed by former rice plantations, now abandoned near Mana [973].

Peatlands in the Mana area• We could find very modest peat deposits 1 km east of Crique Jacques, near Mana. One of

them was revealed to us thanks to the construction work of a fish pond at a private owner’s • The thickness of peat does not exceed 85 cm, but no clean cut could be seen.

¤ from 0 to -5 cm, an abundant litter¤ from -5 to -40 cm, a fibrous to mesic peat showing wood fragments; it has a very dark brown colour, due to

its exposition to open air, as we found blocks of a lighter colour inside ¤ from -40 to -70 cm, a clearly mesic and very dark peat¤ from -70 to -85 cm, a sapric facies of black sticky peat, giving way rapidly to a very homogenous, sticky

and more or less organic clay¤ deeper, sandy-clayey compact facies, hard to penetrate with our corer and very oxidised

Fish pond in construction showing peat, near Mana [973].

Detail of the upper peat, left in the open air

under the sun.

Coring where no peat was found 1

• Among other areas of Guiana that were said to be potentially peaty, were the “Pinot palm”, or “açaí palm” in Portuguese (Euterpe oleracea) formations. They settle in very humid depressions between the hills forming “half-orange” patterns, which are the most structuring morphologic element of the Guyana plateau.

• The prospected site is at Pointe Maripa (commune of Roura), in the heart of a woody area considered as being primary forest

The pedologic coring area at the heart of the Euterpe oleracea station at Pointe Maripa

• The soil was here a gley, laying on a wood accumulation

Coring where no peat was found 2• Our coring concerned a mangrove located north of the small D15 road,

formerly leading to Kourou. To the North-East, that’s to say to The Atlantic Ocean, an Avicennia sp. forest, 150 m wide or so (fig 12), in which we cored extended.

Clay facies between -70 and -100 cm, showing some thin oxidation marks (mangrove at Kourou, along D13 road)

• The soils developed on base marine clay accumulation are typical of the coastal mangrove. Other trials made in the area could not reveal peat levels, not even organic ones.

The pedologic coring area at the heart of the Avicennia sp. mangrove at Kourou [973]

Coring where no peat was found 3

Two areas of the wet savannahs of Guiana have been prospected : • Savane du Galion, in the southwest of Cayenne (Cne of Montsinéry) • the Eleocharis savannahs of Pripris de Yiyi (Cne of Sinnamary, NW Guiana).

Pripris de Yiyi, Sinnamary [973]: general view and coring

Savane du Galion, Montsinéry, near Galion crossroads, and the resullt of the coring we made.

A cartographical study under ARC GIS of the Guyane peatlands starting with the pedological maps of ORSTOM allowed Mariette Mayindza Mouandza to estimate the area covered by histosols where the thickness is superior to 50 cm (pégasse and peat).

The result showed that it was less than the 1640 km2 announced by authors who may have confused “wet zones” and “peatlands”.

The area calculated was 971.5 km², with a large spot being located near Régina.

The compilation of soil maps

Next steps to improve knowledge of the mires in Guiana

• Validate data from soil maps along the coast, going to the field and coring: is peat present, or has it been (if destructions) ?

• What is the hydro-geomorphological context of these peatlands? • Which vegetation corresponds to peatlands (the link is not done

nowadays)? ;• What about mires in the centre of this territory? Mires have been studied on

Venezuelian tepuis*, but there are much bigger and higher than Guiana’s, mountains, whose highest summit is 851 m a.s.l.

* ZINCK, J.A, HUBER, O., 2011, Peatlands of the Western Guyana Highlands, Venezuela. Properties and paleogeographic significance of peats. Springer editions, 295 p.

One aim : visit and core in areas we could not reach; here, peninsula near Cayenne where the presence of peat has

been noted in litterature

Next steps to improve

knowledge of the mires in

Guiana

• What was the impact of Man?: ancient impact of indigenous people on mire, impact of the Jesuits;

• Impact of the different management uses : cutting moucou-moucou • Project of thesis for M. Myindzi-Mouandza with Institut de recherche et de

développement and Université de St-Etienne (concerning the eastern area: Régina, Kaw…).

• Co-operation and exchanges with neighbour countries?

Tracks of ancient drainage, east of Cayenne, north of

Kaw marshes [973], made by the Jesuits?.

Merci de votre attention

We hope that a better knowledge of these peatlands would enable them to be better considered in the local schemes of nature conservation, so that development projects like the one which lead in the 1980’s to rice cultivation on peat soils would no more occur. Education actions may also present the particularities of peatlands and the needs of protection to the public.

“Fête de la science” at Cayenne Teachers’ School, November 2011

Merci de votre attention

• We thank those who helped us at:• Bureau de Recherche en géléogie minière, Cayenne; Institut de recherche

et de développement, Cayenne; Société d’étude et de protection des animaux et de la nature de Guyane (SEPANGUY); Conservatoire du littoral (Sinnamary); Conservatoire d’espaces naturels de Guyane; Herbiers de Cayenne; Direction de l’Environnement et de l’agriculture de Guyane; Office national des forêts, Cayenne; Carole Pourcher;

Merci de votre attention

Gracias por su atención