Terrestrial Ecosystems

Ecosystems are defined in the Convention on Biological Diversity (CBD, UN, 1992) as:
"a dynamic complex of plant, animal and microorganism communities and their non-living environment interacting as a functional unit"
 
Within the framework of the implementation of the Convention on Biodiversity, forest, agricultural, inland water and marine ecosystems were identified as the main ecosystems that harbor biodiversity or biological resources in São Tomé and Príncipe (see section on biodiversity marine) and coastal.
 
Forest Ecosystems
 
Forest ecosystems are ecosystems that have a high density of plants with a very abundant flora, which attracts many organisms to live from its benefits. It is formed by trees that make up the canopy and undergrowth, as well as organisms, rich soils, evolutionary processes and cycles as important for life as the hydrological cycle, the cycle of nutrients, among others. This ecosystem in São Tomé and Príncipe is usually classified by two major dimensions according to the existing bibliography. This is due to: climate and relief characteristics and the degree of anthropogenic modification.
According to the climatic and geological characteristics, the forest ecosystems of the islands can be considered as:
 
- Lowland Forest, from 0 to 800 m altitude: equivalent to the continental forests near Africa. The characteristic species of this formation are, in Sao Tome: Rinoera chevalieri, Zanthoxylum thomensi, Drypetes glagra, Anisophyllea cabole and Sorindeia grandifolea; in Príncipe: Rinorea insularis, Ouratea nutans, casearia mannii, Croton stelluliferus and Erythrococca columnaris.
 
− The mountain forest, from 800 to 1400 m altitude: presents a slow transition of species, with greater variety than in lower altitude formations, but with a similar general appearance. The trees are tall (30 to 40 m), with a dense canopy and the high humidity favors the development of tree ferns, epiphytes, vines and ferns, which cover the trunks of large trees. The tree species characteristic of these formations are: Trichilia grandifolia, Pauridiantha insularis, Pavetta montícola, Erytrococca molleri and Tabernaemontana stenosiphon.
 
A Floresta de névoa, de 1400 a 2024 m de altitude: Caracterizada por grandes chuvas e humidade, com neblina constante e baixas temperaturas, tornando as árvores menores, dominadas por Scheffleras e raramente ultrapassando 10m de altura. As epífitas, em particular orquídeas e fetos, têm um lugar importante nessas formações. As árvores características são: Podocarpus mannii, Baltasaria mannii, Psychotria guerkeana e P. nubicola.
 
− Coastal formations, including riparian forests and mangrove areas. The mangrove is essentially composed of Rhizophora racemosa, R. harrisonii and Avicennia germinans, and occupies small areas, the most important of which are Malanza, Praia das Conchas, Praia dos Tamarindos, Pantufo and Água-Izé, located in the extreme south of São Tomé .

On the other hand, according to the degree of anthropogenic modification, the forest ecosystems of the islands can be considered as:
 
The native (or primary) forest), includes forest areas that have never been cultivated, with little or no human intervention, composed of natural vegetation, with the sporadic presence of some species introduced and favored by human action (for example, Bambusa vulgaris, Musanga cercopioides, Persea americana, Chinchona sp.) . The main limitations to the use of these formations were the location in extremely mountainous relief areas (making access and transformation difficult or impossible), climate, depth and type of soil.
 
− The secondary forest (capoeira)secondary formations of variable age, in which it is still possible to identify vestiges of previous use, namely through the existence of a significant proportion of introduced species. Of the same composition as the shade plantation, where the main distinguishing factor is the presence or absence of coffee or cocoa plants. These are areas that were used for these crops in the past and are now abandoned. Some of these areas were in fact abandoned several decades ago and are tending towards "primary" formation through natural regeneration. The first areas of coffee and cocoa to be abandoned were probably those located on soils with marginal suitability, with steep slopes and difficult access, generally on the edge of the primary forest, and now constitute a transition and protection strip for these formations. Secondary forests are host to many endemic species and act as a buffer, protecting native forest from human influence.

− Shaded plantations, marked by the presence of cocoa or coffee with a shade cover with variable density of natural and introduced species, but mainly Erythrina spp.; these plantations in the mid-nineteenth century covered about 70% of São Tomé; the importance of this shady forest has undergone important variations, mainly due to some attempts to reduce the shade, which may have resulted in reduced soil fertility, strong excursion attacks and armillary infections in cocoa plantations, drastically reducing their production. The species used for shading, in addition to improving cocoa production, also respond to the objectives of food production and quality wood production.
 
− Savannah and other non-forested areas. This includes the northeast region of São Tomé (Praia das Conchas and Lagoa Azul areas), the region of the country with the lowest rainfall (continuous from the trees, in stark contrast to the rest of the country. These formations are believed to have resulted from intense deforestation and frequent fires practiced since the beginning of colonization, mainly in the cultivation of sugar cane. The Adansonia digitata that stands out for its silhouette and the presence of Ziziphus mauritania, Capparis tomentosa, Parkia biglobosa and Borassus aethiopium in this area should also be mentioned .
 

#

Name

Príncipe

São Tomé

Total

Area (ha)

Distribution (%)

Area (ha)

Distribution (%)

Area (ha)

Distribution (%)

1

Native Forest

3.478,50

25,0%

90,8%

22.607,80

26,4%

85,5%

26.086,30

26,2%

86,2%

2

Secondary Forest

4.926,96

35,4%

26.120,30

30,5%

31.047,26

31,2%

3

Shade Plantation

4.237,13

30,4%

24.418,25

28,5%

28.655,38

28,8%

4

Non-Forest

1.274,41

9,2%

9,2%

12.423,30

14,5%

14,5%

13.697,71

13,8%

13,8%

 

TOTAL

13.917

100,0%

100,%

85.569,65

100,0%

100,0%

99.486,65

100,0%

100,0%

Table 1 - Forest Area in São Tomé in 2014 (Soares 2017) and Príncipe in 2016 (Freitas 2019)
 
Agrarian Ecosystems
 Ecosystems are considered to be a dynamic complex of plant, animal and microorganism communities and their environment and which, interacting with each other, form a functional unit. Agricultural ecosystems (or agro-systems) are a particular case, where human intervention is decisive for their characterization and sustainability. In these ecosystems, many plant species are used in the production of food and fuel, in industry, medicine, ornamentation and other purposes. Taking the purpose of the commercial product as a basic criterion, the different plant species existing in São Tomé and Príncipe, whether cultivated or wild species, can be grouped as follows:

  • Industrial Species
Refers to plant species whose final product constitutes raw material for industry. Given the country's weak level of industrial development, these products are almost entirely oriented abroad, thus becoming an immediate source of foreign exchange to cover internal demands in terms of convertible currency. This group includes cocoa (Theobroma cocoa), coconut (Cocus nucifera), olive oil palm (Elaeis guineensis), coffee (Coffea spp.), pepper (Piper nigrum) and vanilla (Vanilla spp. ).
  • Food Species
Food species are those that produce goods that enter directly into the composition of human food, whether fruits, seeds, leaves, roots, tubers or stems. Food species can be divided into annuals and perennials, depending on the life cycle of the plant, and vegetables, fruits, tubers, roots and cereals, depending on the characteristics of the agricultural product, or the part of the plant, that is consumed. like food.

  • Aromatic Species
They include plant species that produce essences with a pleasant aroma or flavor and, for this reason, are greatly exploited by man. Included in this group are plants such as vanilla (Vanila planifolia), cinnamon (Cinnamomum zeylanicum), mycoco (Ocimum viridis), ylang ylang (Cananga odorata), Seal sun zon maia (Erygium foetida), or the Fiá chalela (Cymbopogon citratus).
  • Medicinal Species
Medicinal flora includes plants with a curative effect and therefore used in the treatment of different types of diseases, such as asthma, malaria, wounds, coughs, diabetes, etc. Examples are pau quina (Cinchona spp.), iobot (Onodora myristica), cata d’Obô (Voacanga africana), etc. Other medicinal plant species are associated with these species, such as: dot leaf (Achyranthes aspera), which is used against hemorrhages; salaconta leaf (Canna indica), used against scabies; pau quina (Cinchona spp.), against malaria and bruising; big cat (Rauvolfia dichotoma), against malaria and diabetes; coedane (Cestrum laevigatum), against scabies; macambrará (Craterispermum montanum) and matchanzoche (Syzygium guineense), aphrodisiac plants; stick three (Allophyllus africanus, Allophyllus grandifolius) against malaria and aphrodisiac; matruço (Chenopodium ambrosioides), against worms, diarrhea, massage and contusions, or; mine leaf (Bryophyllum pinnatum), against bruises. These species develop essentially in the Secondary and Primary Forest Zones, although they spread a little throughout the other agroecological zones.
  • Ornamental Species
They are distinguished by the beauty of their flowers or leaves and, for this reason, they are used for ornamentation. Examples are anthuriums (Anthurium andreanum), orchids (Cyrtorchis henriquensiana, Calanthe sylvatica, etc.), parrot beaks (Heliconia rostrata), porcelain roses (Nicolaia elatior), common in the Shadow and Secondary Forest Zones. Experiences carried out in various regions of the country have proven that there are ideal conditions for the production of high quality flowers and foliage. The constraints for the culture of these species are: the lack of investments in their culture; low quality of final products; low number of flower production companies; and lack of conditioned warehouses for the conservation of flowers and foliage.
 
Inland water ecosystems
According to the National Strategy and Action Plan for Biodiversity (2015-2020) the inland water ecosystems of STP are classified as:
  • Lotic waters,
  • Lentics,
  • Brackish
Lotic waters
 
The lotic waters are bodies of flowing water, such as rivers and streams, while the lentic waters are bodies of stationary or still water, such as swamps, marshes, muds. the brackish waters they are formed at the mouths of rivers, that is, at the intersection between fresh and salty sea water. Lotic waters In the set of the two islands there are 116 hydrographic basins and 223 water courses, which vary in length between 5 and 27 km, with waterfalls that vary between 100 and 800 meters.
The hydrographic network of the island of São Tomé has a radial configuration that starts from the highest zone towards the coastline. The largest hydrographic basin is the Iô Grande, with 111.4 km2, followed by the Rio Abade, with 49.5 km2, and the Rio do Ouro, with 46.4 km2 (Lima, 2012). The main rivers of São Tomé and Príncipe are: Iô Grande, Xufe Xufe, Quija, Contador, Água Grande, Abade, Manuel Jorge, Rio de Ouro, Mussacavú, Lembá, Caué, Papagaio and São Tomé, the latter two belonging to the Autonomous Region of Principe. The Malanza (South of S. Tomé) is a large water reservoir that generates controversy regarding its characterization. It is considered by some as the Malanza River, but by others as a lagoon. The country's river network consists of more than 50 rivers. However, its distribution is irregular. More than 60% of river flow is located in the southwest and south of the islands. This fact is related to the higher rainfall recorded in these areas. Indeed, rainfall is very high in this part of the island of São Tomé (5,000 mm/year in the southwest compared to 1,000 mm/year in the city of São Tomé in the north).
On the island of Príncipe, the location of the rivers also follows the characteristics of the relief, with a northern region characterized by a platform with an altitude of 120 180 meters and a slightly disjointed relief, with small elevations and slopes that face the sea (the largest is the 'Precipice', 108 meters high), while the southern region is mountainous, with a strongly rugged relief and valleys with several rivers and streams. There are many walls, peaks and needles, the most prominent of which are Pico Papagaio, João Dias Pai and João Dias Filho.
Rivers can be divided into three strata, according to the characteristics of the ecosystems present, namely:
  • Upper Stratum,
  • Middle Stratum,
  • Lower Course.
Upper Stratum of the rivers encompasses the entire initial part of the rivers, including their sources. The predominant vegetation is primary forest. To the south and southwest of the island of São Tomé, the rivers located in the upper stratum are: Cantador, Lembá, Xufe xufe Quija, Mussucavú and Iô Grande; to the North and East, the rivers: Manuel Jorge, Abade and Ouro. On the island of Príncipe, the Papagaio river is located in the upper stratum. In all rivers in the country, cryptogams (algae, liverworts and mosses) can be observed in this stratum, as well as some herbs, such as Tristemma mauritianum and Rhynchospora corymbosa. With regard to the fauna, it is characterized by the absence of ichthyological species, with only a few planarians, such as turbellarians – small aquatic flatworms (1 to 2 cm) that move by means of cilia.
 
Medium Stratum it covers the entire middle course of the rivers, that is, the intermediate length between the source and the mouth. The fauna consists of small fish, such as Eleotris vittata (charoco) as well as some crustaceans, Atya spp., Macrobrachium spp. and Sicydium bustamantei (freshwater shrimp) lower course corresponds to the lower part of the rivers, in the secondary forest zone and is associated with areas of productive forest. The fauna consists mainly of fish and crustaceans. The presence of birds stands out, such as the Corythornis thomensis (Conóbia, Pica pescado), which feeds on fish found in the rivers. On the banks of the rivers you can find the Phalacrocorax africanus (Water Paw), the Butorides striatus (Chuchu or Black-headed Heron) or the Gallinula chloropus (Water Hen).
 
Lentic waters
Lentic waters are formed inland, like still water, and can be marshes, ponds, mud. S.Tomé has 36 swamps and the main ones are: Morro Peixe, Micoló, Praia Melão, Água Izé, Ribeira Afonso, Angratoldo, Ió Grande and Malanza. Regarding the Autonomous Region of Príncipe, there are 6 main swamps, namely: Água Senhor Padre, Mé Fidel, Lentá Piá, Budo budo, Porto Real and Praia das Burras. The flora of the lentic waters is formed by green algae, with examples of the genera Pandorina, Scenedesmus, Closterium, Cosmarium, and blue algae, including Navicula, Oscillatoria and other diatoms. In the swamps, different species of higher animals can be found, such as the tilapia (Oreochromis niloticus), the water gourd (Periophthalmus barbarus), the bencú (Pelusios castaneus) or the water hen (Gallinula chloropus). . The swamps are also inhabited by inferior beings, which constitute major pathogenic agents, especially for humans. In general, the ecological importance of swamps is not taken into account, characterizing them as simple breeding grounds for the mosquito that causes malaria. Therefore, not much importance is attributed to it as an integral part of inland water ecosystems. However, studies carried out in the country, regarding the case of malaria, have already proven that the breeding grounds of Anopheles gambiae (the mosquito that causes malaria) are not the swamps. According to the evaluation of the performance of the national malaria control program (WHO, 2012), breeding grounds for Anopheles gambiae in São Tomé and Príncipe are, in general, small collections of water exposed to the sun, with or without vegetation .
Within the lentic waters we also have lakes and ponds, the best example of which in São Tomé and Príncipe is Lagoa Amélia, located in the center of São Tomé (district of Mê Zochi), located in the crater of an ancient volcano. In recent years, the lagoon space has been invaded by lianas, modifying the physiognomy and floristic composition of the botanical association of Begonia baccata and Cyathea spp. On the other hand, most of the former caldera is invaded by shrubs (Anthocleista scandens – Gentianaceae). The greatest risk is the disappearance of the original ecosystem, with negative consequences for the conservation of endemic species that depend on this habitat.

Brackish Water
This ecosystem is formed by a mixture of fresh and salt water, thus constituting a unique ecosystem, where characteristic animals and plants can be found. With regard to plants, the highlight goes to the existence of mangroves. The vegetation of brackish waters is very special, but poor in plant species. It is dominated by Rhizophora mangle and Rhizophora racemosa, both trees with aerial roots, and Avicennia germinans provided with pneumatophores. The mangroves are also nesting areas for birds, with emphasis on the Phalacrocorax africanus (water ducks), the Gallinula chloropus (water hen) and the Egretta intermedia (white heron) which has a vast colony in the Água Izé area, as well as at Praia das Conchas (the latter with a lower density compared to Água Izé). Regardless of the fish that come from sea water and temporarily live in this ecosystem, there are species such as the Periophthalmus barbus (cucumba) that is characteristic of this ecosystem. The brackish water ecosystem is very important for the preservation of many species, especially saltwater fish that use these habitats to reproduce.
 
Coastal Ecosystems
The coastal zone and the marine environment constitute an integrated resource and an essential component of the environment, offering valuable possibilities for achieving sustainable development in S.Tomé and Príncipe.
These ecosystems are populated by a high variety of plant species, from inferior to superior beings. Inferior plants are generally part of the phytoplankton, being fundamentally constituted by macro and microscopic algae, without flowers, with a rudimentary organization, the body shredded in cells and always having pigments. As an example, we observe the presence of green algae (from the Chlorophyceae class, such as Dunaliella salina), blue algae (Cyanophyceae) and brown algae (Phaeophyceae, such as Fucus platycarpus), which sometimes appear during low tide, and also Rhodophyceae (brown algae). In coastal superior plants predominate the coconut tree (Cocus nucifera), turtle leaf (Ipomea pes caprae), water libo (Struchium sparganphora), tamarind (Tamarindus indica), banana tree (Musa spp.), sweet caroceiro (Terminalia catappa ), juniper (Ziziphus abyssinica), micondó (Adansonia digitata), lemon (Ximenia americana), bamboo (Bambusa vulgaris), fruit tree (Artocarpus altilis), boldrega leaf (Portulaca oleracea). In the coastal ecosystem there are also mangroves, whose dominant species are Rhizophora mangle (Rhizophoraceae) and Avicennia germians (Avicenniaceae). These species occur along the lower course and at the mouths of some rivers (Malanza, São João de Angolares, Praia Grande and Lagoa Malanza. It should be noted that currently on the island of Príncipe the few areas of mangroves, all of them undeveloped, concentrate on the southeast edge of the island and the Príncipe Natural Park (PNP), between Praia Grande and Praia Seca, and on Praia Lapa, in Baia das Agulhas.
São Tomé, 26 de Julho de 2023