Segunda parte
(Second part - Deuxième partie)

RESUMENES POR PAIS

(COUNTRY BRIEFS - RESUMES PAR PAYS) (continuar)

GUYANA

Guyana covers 214 970 km² between latitudes 2° and 8° north and longitudes 57° and 61° west. The maximum distance inland from its 430 km long coastline, is about 870 km. It is bounded by Venezuela, Brazil and Surinam. Four main regions can be distinguished (2):

• the northern coastal belt, consisting of low-lying alluvium with a varying width, up to a maximum of 65 km inland (in the east). Its elevation is often up to one meter below sea level. This is the main agricultural zone of the country;

• the lowland region of undulating forest land, covering most of the northern and central parts of the country, generally below 150 m and consisting of broad belts of white sand;

• the Pakaraima mountain region in the west, an elevated table land of sandstone escarpments between 300 and 1 200 m in elevation, corresponding to similar formations in the southeast of the Venezuelan Guyana and the Brazilian territory of Roraima;

• the southern uplands, a vast area mostly over 150 m in elevation and covered with undulating forest land.

The country has many rivers, generally running from south to north, towards the Atlantic Ocean. The main streams (Essequibo, Demerara and Berbice) are navigable in their lower reaches for distances of between 60 and 160 km. Rainfall varies from about 2 300 mm in two rainy seasons (April–August and November–January) in the coastal area, to 1 500 mm in one rainy season (May–August) in the Rupunumi region, south of the Pakaraima mountains.

The population is estimated at 880 000 habitants in 1980; more than 90% of it live in the coastal strip.

1. Present situation

1.1 Natural woody vegetation

1.1.1 Description of the vegetation types

Six major forest formations are recognized, each with one or more distinctive types, identified by the dominance of certain species. The following description is essentially based on the detailed vegetation study by Fanshawe (1).

Closed broadleaved forests (NHC)

(a) Rain forest (locally called “mixed forest”) occurs on well drained sites from the flat plain to broken areas on brown sands, loams or red earth. It has three and occasionally four storeys. The upper canopy attains 20–40 meters, with emergents up to 50 m. The lower storey lies between 13 and 20 m. The undergrowth ranges between 3 to 13 m with few shrubs. Ground cover is sparse. There are from 80 to 100 woody species (height more than 4,5 m) per ha. Two species are well represented in the upper storey: Eschweilera sagotiana and Licania heteromorpha. Lianes are occasional to common. Only a few palms occur. Legumes correspond to 5 to 30% of the total number of individuals depending on whether the dominant tree is of the same family or not.

In the lowland region the rain forest occurs from the Venezuelan border to the Demerara river in the east and from the coastal belt south to the Pakaraima mountains. This large area is covered practically by one association: Eschweilera - Licania. The other association occurring is Eschweilera - Dicymbe, which can be considered as a transition between the Dicymbe forests of the Pakaraima region and the lowland forests. The only difference is the floristic composition. In the Eschweilera - Licania association predominants include: purpleheart (Peltogyne venosa), Hymenaea davisii, Couratari pulchra and Pithecellobium pedicellare. Canopy dominants are kakaralli (Eschweilera sagotiana), wirimiri (E. confertiflora), kautaballi (Licania venenosa), greenheart (Ocotea rodiaei), morabukea (Mora gonggrijpii), haiariballi (Alexa imperatricis), Catostemma commune, Pouteria guianensis and Aspidosperma excelsum. The Eschweilera - Dicymbe association occurs on red earth and brown sands in a narrow belt along the base of the Pakaraima escarpment. Canopy dominants are kakaralli, clump wallaba (Dicymbe altsoni), Eperua falcata and monkey pot (Eschweilera sp.). In the lower storey Licania heteromorpha, Parinari barbatum and Duguetia sp. are dominant. There are more legumes than in the previous association.

In the Pakaraima mountain region the rain forest occurs on red earth derived from intensive vulcanic rocks. Two associations are found. The Eschweilera - Licania association with morabukea or haiariballi and others such as crabwood (Carapa guianensis) and bulletwood (Manilkara bidentata). The Eschweilera - Dicymbe association is strongly dominated by Dicymbe altsoni (over 40%).

(b) Seasonal forest is found on well drained sites, with a marked seasonal distribution in rainfall.

The evergreen seasonal forest is a three storeyed forest, with an open canopy between 27 and 40 m, a discontinuous lower storey from 18–23 m and a fairly dense undergrowth between 6 and 15 m. Palms are fairly frequent in the undergrowth. It is found in the lowland region, from the Essequibo river to the Courantyne river. Canopy dominants are kabukalli (Goupia glabra), wamara (Swartzia leiocalycina), bulletwood, Terminalia amazonia, Aspidosperma excelsum and others. In the lower storey, the palm Maximiliana regia is often dominant. The evergreen seasonal forest is not represented in the Pakaraima region, nor in the southern upland region.

The semi-evergreen seasonal forest has two storeys with deciduous species in the canopy (20 m high). Evergreen species occur in the understorey (6–12 m). The semi-evergreen seasonal forest is widespread in the Rupunumi district of the lowland region on the low gravelly hillocks in the savanna. Canopy dominants include taparai (Cordia alliodora) kartang (Centrolobium paraense), Acacia polyphylla and Enterolobium spp.; Myrtaceae dominate the shrub layer. The same type of forest occurs also in the Pakaraima region on the foothills of the savanna mountains the southwest of the Kanuku mountans and in the southern upland region.

(c) Dry evergreen forest: this type of forest occurs either where excessive drainage exists with normal evaporation (on the white sand peneplaine and where soils are thin and/or rocky) or where evaporation is excessive due to strong winds with normal drainage. On the white sand peneplaine the ground water-table is higher going from the watershed towards the edge of the peneplaine, giving a characteristic transition from xeromorphic scrub, xeromorphic woodland to wallaba forest.

The wallaba forest is three storeyed, with a closed canopy between 25 to 35 m high, a discontinuous understorey 12 to 25 m high and a dense undergrowth from 6 to 12 m. Large trees and lianes are scarce. Palms are abundant in the shrub layer and epiphytes are many. In the lowland region the wallabafforest occurs on the white sand peneplaine over an area going from the Pakaraima escarpment to the coastal region and from the Cuyuni to the Courantyne river, and continues over a wide area of the lowland region in Surinam. The main dominant species are: wallaba (Eperua falcata) and ituri (E. grandiflora). Other canopy dominants are: Catostemma fragrans, bulletwood, Licania buxifolia, Terminalia amazonia, Eschweilera corrugata, Aspidosperma excelsum and apokwito (Cassia apoucouita). In the Pakaraima region the dominant species are: Eperua falcata and E. jenmani. Others are: Cassia spp. Dicymbe corymbosa, Dimorphandra congestiflora.

The xeromorphic rain forest is two storeyed with a dense canopy 6 to 13 m high. There is a discontinuous, emergent layer between 18 and 25 m. The forest is almost entirely evergreen. In the lowland region it occurs on thin and loamy soil. The canopy is dominated by Pithecellobium spp., Rinorea spp. and Eugenia sp. Among the emergents are Pithecellobium collinum, Pisonia sp. and bulletwood. In the southern upland region the xeromorphic rain forest is characteristic of steep slopes with thin soils. The most common emergent species are: Peltogyne porphyrocardia, Manilkara excelsa, Aspidosperma ulei and Apeiba schomburgkii.

The xeromorphic woodland is two storeyed, with a low canopy (6–12 m) and a dense or sparse undergrowth. In the lowland region it occurs on the white sands and might be secondary, at least in parts, as this area is recurrently swept by fire. The canopy consists almost entirely of Clusia fockeana. In the Pakaraima region the main species are kaishak (Dicymbe jenmani) and Moronobea jenmani. In the southern upland region xeromorphic woodland is found on almost bare rock slopes. Canopy dominants are: Erythroxylum and Clusia spp.

(d) The montane forest is two storeyed and rich with a canopy between 24 and 36 m and a lower storey between 6 and 18 m. It occurs on Mount Roraima in the southern upland region where bulletwood and others dominate.

(e) The marsh forest is characterised by marked seasonal fluctuations in the moisture conditions from very dry to water-logged and is always associated with impeded drainage. It is found on alluvial silt and on peat (“pegasse”). It is two or three storeyed with only 5% of palms. The canopy is low (9–15 m) with an emergent layer between 15 and 25 m. In the coastal region most of the pegasse land in the northwest district has marsh forest dominated by kirikana (Iryanthera macrophylla) and Tabebuia insignis. On alluvium there is less ground cover and smaller maximum tree diameter. Canopy dominants are warakosa (Inga edulis) and lanaballi (Gustavia angusta). Similar marsh forests occur in the lowland region. In the southern upland region they take the form of gallery forests on grey silt, with wichabai (Manilkara amazonica) and duru (Apeiba schamburgkii).

The palm marsh forest is two storeyed and palms are dominant. Canopy is between 5 and 15 m. Emergent trees, with or without palms, reach 12–30 m. Shruba are present. In the coastal region the palm marsh forest occurs on pegasse or the river banks in the west in very homogeneous stands. Main emergent species include manni (Symphonia globulifera), white cedar (Tabebuia insignis) and manicole (Euterpe edulis). Virola surinamensis (dalli) has to be added in the lowland region.

The palm marsh woodland is a low woodland with emergent palms or trees up to 18 m, without shrub layer. There are only about 20 species. Stilt roots are common. In the lowland region palm marsh woodland is fairly frequent east of the Essequibo river on pegasse. Canopy species include Clusia fockeana, Cyrilla antillana and Tabebuis insignis.

The marsh woodland is low and dense, consisting of small trees with spreading branches and with dense undergrowth. It forms galleries in the savanna along the streams in the southern upland region.

(f) The swamp forest has an almost permanent wet soil. The shorter the period of inundation, the nearer the forest approaches the rain forest, and the longer the period, the poorer the vegetation. It is one storeyed and has an open canopy between 18 and 25 m, composed of trees and palms. It occurs on all year round water-logged sites. Dominant trees include Pterocarpus officinalis, Virola sp. and Macrolobium spp. and Euterpe edulis

Mora forests occur on sites with impeded drainage and form a zone of variable width along the wnterways. It is three-storeyed, with a more or less closed canopy at 30 to 45 m. a lower storey from 15 to 25 m and undergrowth between 6 and 12 m. Mora excelsa is markedly dominant. Among other canopy dominants are crabwood, Pterocarpus officinalis, Macrolobium bifolium, Eschweilers spp. and Catostemna spp.

(g) Mangroves spread along the tlantic coast in brackish waters. The canopy is at best 20–25 m but often drops to 12 m. The four caribean genera Rhizophora, Avicennia, Laguncularia and Conocarpus are represented.

Open broadleaved forests and scrub vegetation (NHc/NHO and nH)

The palm marsh known as ite savanna (Mauritia flexuosa) is widespread in the coastal region behind the cultivated belt and in the lowland region. Groundcover consists of grasses.

The savannas correspond to a pronounced alteration of moisture and drought, together with shallow soil and the presence of a clay or iron pan or sheet rock. They are classified as intermediate (lowland), far interior and upland (Pakaraima plateau). The intermediate savannas extend from the Demarara river to the Courantyne. The far interior savannas, located in Rupunumi are divided in a northern and southern section, separated by the Kanuku mountains. They form part of the Brazilian Rio Branco savannas. The northwest while sand moist savannas are an extension of the Venezuelan Gran Sabana. The dominant vegetation is a bunch-grass and sedge complex with, on deeper soils, low gnarled trees: Curatella americana, Byrsonima crassifolia.

Swamp woodland and arborescent swamp are two types occupying relatively minor areas, consisting respectively of low spreading trees at the riparian fringes and dense shrub on sand banks or silt.

Thorn woodland dominated by spiny trees of Fagara sp. and Bauhinia sp. occurs in a narrow belt at the very base of the foothills in the southern upland region.

1.1.2 Present situation of the woody vegetation Present areas

The following table estimates the various areas of the different categories of woody vegetation covering in total about 84% of the area of the country:

Areas of natural woody vegetation estimated at end 1980
(in thousand ha)

¹ of which 12 (thousand ha) correspond to a national park (NHCf2r = 12)

The above area figures are based on (2); the following assumptions were arrived at: about 1% of the savanna area mentioned in (2) of 2 250 000 ha corresponds to open palm forest, and about 5% of the same area correspond to shrub vegetation (the document mentions that “on deeper soils” Curatella americana and Byrsonima occur). In addition, it was estimated that about 10% of the productive closed forest (NHCf1) have already been creamed (NHCf1uc).

Montane forest, half of the swamp and marsh area and all of the mangrove area (150 000 ha approximately) have been classified as improductive closed forest (NHCf2). The area affected by shifting cultivation was tentatively estimated at 200 000 ha. According to (4) the mangroves cover, west of the Essequibo river, an area of 91 000 ha.

Ownership

A distinction is made between the state forest area (totalling 8 780 000 ha approximately in 1973) and state lands which cover an additional 8 730 000 ha. (9) Most of the latter area is covered by forest so that the state owns almost all the forests.

Legal status and management

The Kaieteur national park covers an area of 12 000 ha approximately in the forest (NHCf2r = 12).

There is no intensive forest management in the sense used in this study, although it is intended to develop it (NHCf1m = 0).

Forest utilization

Log harvesting

The forests are divided into two main zones: the “more accessible forest area”, covering 4 920 000 ha and located immediately close to the agricultural zone and the more interior and “inaccessible” forests. The state forests in the more accessible zones are leased for a determined period. The lease may cover only small areas (less than 200 ha) up to 20 000 ha and in special cases even more. In 1973 the total forest area leased amounted to 790 000 ha. In addition, permission to cut specific quantities of forest products are issued.

Of the wood species, greenheart accounts for 62% of total timber production of the state forests. Other important species include purpleheart, wallaba, kabukalli, crabwood, mora and tauroniro (Humiria balsimifera). The Bartica triangle, limited by the Essequibo, the Mazarumi and the Potaro rivers produced 74% of the total sawlog output in the late 60's (8).

The volume per ha of greenheart, extracted from the concession areas varies from 10 to 35 m³ per ha, while the volume of utilizable wood for timber would be between 52 and 70 m³/ha (8). It is estimated that the average output per ha for the country must be around 20 m³. The FAO Yearbook of Forest Products shows the following production figures of veneer and sawlogs for Guyana.

Average annual production of sawlogs and veneer logs
(in thousand of m³)

Consequently, the average area logged every year in the 1976–1980 period would be of the order of 210 000 m³/20 m³/ha, or 10 500 ha. According to (9) private forests produce 5 000 m³/year.

Other products

The fuelwood production was, in 1973 slightly over 10 000 m³ and charcoal production amounted to 345 tons only. Production of both commodities seems to be fairly constant.

Mangrove bark extracted from Rhizophora mangle in the Waini river swamps, reached a production of 225 tons in 1973 which were used in the local tanning industry.

1.1.3 Present situation of the growing stock

Growing stock estimated at end 1980
(totals in million m³)

(3) mentions for an enumerated area of about 200 ha of logged-over mixed forest a gross volume of 96 m³/ha (under bark, DBH ≥30 cm). On the other hand (5) gives for a virgin forest area of 127 000 ha located in the Bartika triangle a much higher volume, 223 m³ per ha (under bark, DBH≥30 cm.) However this area is considered as being very rich. In the neighbouring Venezuelan region an inventory of 235 000 ha of forest gives an average gross volume VOB (over bark, DBH≥10 cm) equal to 190 m³/ha. The average VOB taken for virgin forests of Surinam is 210 m³/ha. It seems reasonable to use this latter figures also for the virgin forests of Guyana, being intermediate between the two other figures available for Guyana once corrected to correspond with the VOB volume concept (corrected figures are approximately 135 m³/ha and 315 m³/ha). The average VOB for logged-over forests will be taken equal to: 210 - 2 × VAC = 170 m³/ha. A figure of 100 m³/ha will be adopted for improductive forests (NHCf2).

No information was found on increment in natural forests.

1.2 Plantations

1.2.1 Introduction

The first plantation of Pinus caribaea was carried out in the mid 50's. In 1960 around 50 ha had been planted, in 1965 130 ha, in 1970 250 ha. At the end of 1975 the total area planted amounted to 660 ha.

1.2.2 Areas of established plantations

Areas of established industrial plantations estimated at end 1980
(in thousand ha)

1.2.3 Plantation characteristics (1)

Mean annual increments on plantations of 13 years have been found equal between 3.8 m³/ha and 7.7 m³/ha depending on site (10). In the same document it is estimated that a figure of 13.5 m³/ha /year could be obtained over a 15-year rotation on selected sites.

2. Present trends

2.1 Natural woody vegetation

2.1.1 Deforestation

Average annual deforestation
(in thousand ha)

Periods

1976–80 and 1981–85

As there are no precise figures available on deforestation, it has been estimated that permanent agriculture, mining, roads, etc., account for 500 ha per year and shifting cultivation for another 1 500 ha per year, figures which are similar to those adopted in Surinam, taking into account the larger agricultural population one one side and the absence of large-scale planting in Guyana.

Areas of natural woody vegetation estimated at end 1985
(in thousand ha)

2.1.2 Degradation

There are, locally, some fires during the dry season. However, degradation is not considered to be of sizeable importance.

2.1.3 Trends in forest utilization

A slight gradual increase might be expected in the number of species used as greenheart becomes more and more scarce; the output per ha however, should remain about the same. Total production might increase a little, say around 250 000 m³ per year by 1985.

2.2 Plantations

Areas of established industrial plantations estimated at end 1985
(in thousand ha)

Bibliography

(1) Fanshawe, D.B. 1952 “The Vegetation of British Guyana - A Preliminary Review” - Institute paper No. 29 - I.F.I.-Oxford

(2) FAO 1963 “Forest Inventory”-based on the work of T.I. Ress - Report No. 1762 - Rome

(3) FAO 1970 “Forest Industries Development Survey - Enumeration of the Portable Sawmill Area”-based on the work of R. de Milde and D. de Groot - FO:SF/GUY 9 Technical Report No. 5 - Georgetown

(4) FAO 1970 “Forest Industries Development Survey - Reconnaissance Survey of the More Accessible Forest Areas”-based on the work of R.de Milde and D. de Groot - FO:SF/GUY 9 Technical Report No. 8 - Georgetown

(5) FAO 1970 “Forest Industries Development Survey - Inventory of the Ebini-Itaki Area”-based on the work of R. de Milde and D. de Groot - FO:SF/GUY 9 Technical Report No.9 - Georgetown

(6) FAO 1970 “Forest Industries Development Survey - Inventory of a Selected Area in the Northwest District”-based on the work of R. de Milde and D. de Groot-FO:SF/GUY 9 Technical Report No. 10 - Rome

(7) FAO 1970 “Forest Industries Development Survey - Reconnaissance Survey of the Southern Part of Guyana” -based on the work of R. de Milde and D. de Groot - FO:SF/GUY 9 Technical Report No. 15 - Rome

(8) FAO 1970 “Forest Industries Development Survey - Report on Project Results, Conclusions and Recommendations” - FO:SF/GUY 9 Terminal Report -Rome

(9) Ministry of Energy and Natural Resources - 1973 “Annual Report of the Forest Department for the Year 1973” - Georgetown

(10) FAO 1977 “Logging and Mechanical Forest Industries Demonstration and Training - Phase I - The Potential for the Establishment of Long-Fibre Pulp Plantations in Guyana” - based on the work of D.K. Paul - FO:DP/GUY/75/004 Working Document 1 - Rome

Annex 1

Distribution of areas of the three Guyanas according to Unesco classification

(Unesco/C.I.T.V. Vegetation Map of South America)

GUYANE FRANCAISE

La Guyane Française est le plus petit des trois pays guyanais, et s'étend sur environ 91 000 km². Ses voisins sont le Surinam à l'ouest et le Brésil au sud et à l'est. La forêt couvre plus de 90% de sa superficie. Ses frontières sont constituées par les rivières Maroni à l'ouest et Oyapocle à l'est. On peut utiliser la division en régions naturelles suivante:

• le secteur côtier des terres basses: les sols dans cette région sont d'origine alluviale marine. On distingue deux zones, l'une à tendance sèche dite des “terres basses sous le vent de Cayenne” (1800–2500 mm de pluviosité) et l'autre, humide dite des “terres basses au vent de Cayenne” (2500–3500 mm);

• le secteur médian et subcôtier, comprenant la chaîne septentrionale et le massif central. La pluviosité peut être moyenne (200–3500 mm par an) à très forte (3500–8000 mm par an): cette variabilité influe sur la végetation;

• le secteur de la chaîne Inini - Camopi, essentiellement sur “roches vertes”, avec une pluvosité de 2000 à 3000 mm;

• le secteur méridional et la pénéplaine du sud, avec une pluvosité de l'ordre de 2000 mm. On distingue ici la zone des grandes plaines alluviales et celle des collines et “inselbergs”

1. Situation actuelle

1.1. Végétation ligneuse naturelle

1.1.1. Description des types de végétation

On peut classer la végétation comme suit (7):

Formations forestières feuillues denses (NHC)

Formations littorales halophiles et psammophiles: les mangroves se répartissent sur une frange côtière de largeur variant entre quelques mètres à quelques kilomètres. On rencontre des peuplements purs de palétuvier blanc (Avicennia nitida), bordé en front de mer par Laguncularia racemosa et parfois par des graminées. Le long des estuaires le palétuvier blanc est remplacé par le palétuvier rouge (Rhizophora mangle). Plus à l'intérieur, les paletuviers se mêlent au palmier-bâche (Mauritia flexuosa), qui domine généralement, et au montarchi (Pterocarpus officinalis), arbres aux contreforts caractéristiques (“acabas”). Des formations herbeuses jouxtent souvent les mangroves.

Forêt de terre ferme sur sol argileux: la forêt dense est constituée par trois étages, les arbres émergents atteignant jusqu'à 50–60 m de haut. La voûte est relativement élevée et dense, et le sous-bois clair, pauvre en herbes et en palmiers. Lorsqu'apparaissent des facteurs limitants, par exemple un sol mince et asphyxiant, et dans les zones de chablis (causés par des arbres tombés), le sous-bois devient dense et broussailleux et contient de nombreuses lianes. Quelques essences de l'étage dominant sont: angélique (Dicorinia guianensis), bois-violet (Peltogyne sp.), wapa ¹ (Eperua falcata), wacapou (Vouacapoua americana), Pithecellobium racemosum, Parkia spp., Swarztia spp., Lecythis spp., Eschweilera spp., Vochysia spp., Licania spp., Ocotea spp., balata franc (Manilkara bidentata), Goupia sp., fromager (Ceiba pentandra), simarouba (Simarouba amara). Les palmiers sont rares dans l'étage dominant (par exemple Iriartea et Oenocarpus). Les arbres du sous-bois appartiennent souvent aux mêmes familles que celles de l'étage dominant. Annona, Duguetia et Xylopia sont des exceptions. Les palmiers y sont parfois fréquents: Bactris spp., Astrocaryum spp., Geonoma spp.

Forêt sur cuirasse latéritique: on la rencontre uniquement dans le nord-ouest du pays, sur le sommet des plateaux dans la région d'Organabo-Mana et de Saint Jean du Maroni. Les arbres sont peu élevés et tortueux, les sous bois broussailleux. Quelques espèces caractéristiques sont Clusia fockeana, Matayba opaca, Myrcia sylvatia.

Forêts marécageuses: on les trouve le long des certains rivières (“criques”) d'eau stagnante, ou au bord de grands cours d'eau, surtout dans la région des rivières de Kaw, Courouare et Ouanary. La forêt est assez pauvre, sauf dans les zones de transition à la forêt de terre ferme. Les palmiers sont bien representés, notamment Euterpe oleracea ² (“pinots” ou “wassaies”), qui peut former des peuplements étendus quasiment purs appelés “pinotières”. Les autres palmiers abondants sont: Mauritia flexuosa dans la zone côtière le long des estuaires, et Manicaria saccifera. Dans le sous-bois en doit mentionner Geonoma baculifera, Bactris acanthocarpoídes et Astrocaryum paramaca. Des espèces de grandes dimensions se mêlent aux pinots tels que manil (Symphonia globulifera), yayamadou ³ (Virola surinamensis) et maukouchis (Pterocarpus officinalis).

Dans les zones de transition on rencontre carapa (Carapa guianensis), Caryocar microcarpum, Macoubea guianensis, Cordia tetranda, Eschweilera subglandulosa, E. corrugata, Parinari campestris, Jacaranda spp, fromager, Hura crepitans.

La végétation ripicole le long des fleuves et des criques a un aspect divers selon la configuration de la berge. Le long des rives concaves, la forêt de terre ferme atteint la rive, et sur les pentes humides abondent les wapas (Eperua falcata), le courbaril (Hymenaea courbaril), le tachi (Tachigalia paniculata) et Bombax aquaticum. Le long de rives convexes on rencontre la formation “pris-pris” avec des arbres isolés de taille moyenne, Cecropia spp., Triplaris surinamensis, émergeant d'une végetation très dense de quelques mètres de haut, consistant surtout de Inga spp., Croton cuneatus, Montrichardia arborescens.

Les forêts de moyenne altitude: les zones submontagnardes (plus de 500 m) sont rares en Guyane et sont localisées, à quelques exceptions près, le long de la chaîne Inini-Camopi, où se trouvent les plus hauts sommets de la Guyane (860 m). Sur les pentes douces la forêt est bien structurée, les fûts élevés et rectilignes. Par contre, sur les sommets, souvent recouverts d'une épaisse cuirasse latéritique la forêt présente un aspect broussailleux. Des brouillards épais persistent jusqu'à une heure avancée de la journée surtout en saison des pluies. La forêt est floristiquement assez pauvre (les Sapotacées sont cependant bien representées), mais il existe de nombreuses espèces endémiques.

¹ Wallaba au Surinam et en Guyana.
² Palmito au Brésil et au Vénézuéla.
³ Baboen au Surinam.

Formations forestières feuillues ouvertes (NHc/NHO)

Dans le secteur des terres basses, on rencontre aussi des savanes, très souvent inondées, avec des arbres disseminés de Mimosa pigra sur les terrains inondés, et, sur les sols mieux drainés, de petit balisier (Heliconia psittacorum). Il existe aussi les marécages à broussailles ou les “savanes à pruniers” avec prunier (Chrysobalanus icaco), Pterocarpus officinalis, Tabebuia sp., Annona glabra, Triplaris surinamensis et Mauritia flexuosa (pouvant atteindre 30 m de hauteur).

Formations essentiellement arbustives (nH)

Sur les zones côtières sableuses on rencontre parfois une végétation arbustive, composée par exemple de Hibiscus tiliaceus.

1.1.2. Situation actuelle de la couverture ligneuse

Surfaces actuelles

Surfaces estimées de végetation ligneuse naturelle à la fin de 1980
(en milliers d'ha)

Les chiffres sont principalement basés sur la carte du document (7). On a supposé que la superficie de la catégorie “forêt fréquemment inondable et marécage” correspond pour 60 % à NHCf1 et pour 40 % à NHCf2. De la même manière on a consideré que la “forêt de plaine et pente douce” correspond pour 90 % à NHCf1 et pour 10 % à NHCf2. Les mangroves (55 000 ha environ) ont été classées en NHCf2.

Proprieté

La quasi totalité des forêts sont domaniales.

Statut légal et aménagement

Selon l'information disponible il n'existe pas de forêts ayant un statut special (NHCf2r=0)

Le service forestier de Guyane française a entrepris dès 1954, souvent en collaboration avec le service forestier du Surinam une série d'essais relatifs à la croissance des peuplements en forêt uaturelle et à la regénération et enrichissement en essences locales après exploitation. Ces essais ont été repris et amplifiés récemment avec l'aide de divers organismes de recherche. Il n'existe pas cependant actuellement de surfaces significatives de forêts aménagées intensivement au sens de cette étude (NHCf1m=0).

Exploitation forestière

La production de grumes s'est tenu au niveau modeste de 30 000 m³/an durant la période 1970–75 mais elle est depuis lors en progression constante. Elle a attaient 75 000 m³ en 1978 et 85 000 m³ en 1979.

Compte-tenu des difficultés particulières à la région, la situation des entreprises reste encore précaire, mais l'on peut estimer raisonnablement que la production de grumes de bois d'oeuvre pourra atteindre et même dépasser 200 000 m³ dans le courant des années 80. Certaines entreprises exploitent déjà de façon systématique près de quarante essences, représentant un volume de 15 à 30 m³/ha.

Parmi les essences commerciales les plus importantes on distingue: angélique, kouali (Vochysia sp.) gonfolo (Qualea sp.), yayamadou, wacapou, balata franc, St. Martin (Andira sp.), grignon franc (Ocotea rubra), manil et carapa. (2) L'exploitation du yayamadou dans des zones marécageuses produit des grumes exportées au Surinam (3).

La production annuelle de bois de feu et bois pour le charbon de bois est estimée à environ 15 000 m3 par l'annuaire FAO des produits forestiers lequel indique une production annuelle de 5 000 m3 d'“autres bois ronds industriels” (essentiellement perches et poteaux).

1.1.3. Situation actuelle des volumes sur pied

Volumes sur pied estimés à la fin de 1980
(totaux en millions de m3)

Sur 163 000 ha de formations forestières dans la zone de Kourou (6) on a trouvé un volume brut sur écorce des arbres de diamètre supérieur à 20 centimètres égal à 273 m3 (dont 62 m3 pour le deux essences économiquement les plus importantes -angélique et wapa). Ce même volume est égal à 265 m3 (dont 53 m3 pour l'ensemble angélique et wapa) sur les 165000 ha de forêts dans la région de Saint Laurent du Maroni (6), et à 268 m3 (dont 85 m3 pour angélique et wapa) sur 159 000 ha dans la région de Cayenne. Les résultats concordants pour les forêts de la région littorale amènent à adopter un volume brut moyen sur écorce des arbres de diamètre supérieur à 10 cm (VOB) égal à 290 m3. Cependant ce chiffre est nettement supérieur à celui adopté pour le Surinam voisin (210 m3) et il reste à determiner quelles sont les raisons de cette différence.

Des comptages effectués en mangrove jeunes et adultes (4) donnent un volume brut moyen (D ≥ 5 cm sur écorce) de 200 m3 environ qui a été adopté comme VOB pour les forêts “improductives” (NHCf2) en l'absence d'informations sur les autres types de forêts “improductives” (forêts sur les fortes pentes en particulier).

1.2. Plantations

L'introduction expérimentale d'essences à croissance rapide (Pinus caribaea, Eucalyptus spp.) s'est faite à partir de 1960. Les essais de 1960 à 1970 couvrent 160 ha et ceux de la periode 1976–80 300 ha. Ces recherches ont pour objectif la production de bois à pâte et de bois a faible prix de revient pour les emplois ordinaires (coffrage, charpente légère, bois d'industrie et bois de feu). Toutefois ces plantations ne sont pas encore réalisées à l'échelle industrielle et ne fournissent aucune production commercialisée.

2. Tendances actuelles

2.1. Végétation ligneuse naturelle

2.1.1. Déforestation

Déforestation annuelle moyenne
(en milliers d'ha)

Périodes: 1976–1980 et 1981–1985

La déforestation est minime compte-tenu de la très faibles population agricole dans le pays (la population totale est de 65 000 habitants environ).

Surfaces estimées de végétation ligneuse naturelle à la fin de 1985
(en milliers d'ha)

Le tableau suivant donne les volumes sur pied à la fin de 1985.

Volumes sur pied estimés à la fin de 1985
(en millions de m3)

2.1.2. Tendances dans l'exploitation forestière

On ne prévoit pas de changements essentiels dans l'exploitation forestière d'ici 1985.

2.2. Plantations

Il ne devrait pas y avoir de plantation à l'échelle industrielle avant 1985.

Bibliographie

(1) Aubréville, A. 1961 “Aperçus sur la forêt de la Guyane Française” - dans: Bois et Forêts des Tropiques no. 80 - Nogent-sur-Marne (France)

(2) Grivaz, G. 1966 “La forêt et l'essor de l'économie forestière de la Guyane Française” - dans: Bois et Forêts des Tropiques no. 105 - Nogent-sur-Marne (France)

(3) Grivaz, G. 1972 “Exploitation forestière Guyanaise” - CTFT - Nogent-sur-Marne (France)

(4) Centre Technique Forestier Tropical 1972 “Mangroves de Guyane - Reconnaissance rapide” - Nogent-sur-Marne (France)

(5) Centre Technique Forestier Tropical 1975 “Evaluation du potentiel ligneux de quatre zones forestières de 20 000 hectares” - Nogent-sur-Marne (France)

(6) Centre Technique Forestier Tropical 1975 “Inventaire papetier en Guyane Française” - Fascicules I, II, III et IV- Nogent-sur-Marne (France)

(7) Centre d'Etudes de Géographie Tropicale 1979 “Atlas des départements d'outre-mer” - Talence (France)

Annexe I

Distribution de la surface totale des trois Guyane en fonction de la classification de la végétation de l'Unesco (Carte Unesco/C.I.T.V. de la végétation d'Amerique du Sud)

(en milliers d'ha)