Terrestrial Threats

Human activities are reshaping biological communities and affecting the functioning of ecosystems across the Earth. Climate change, land use change and habitat fragmentation, overexploitation, pollution and invasive alien species have been recognized as the most important and widespread direct anthropogenic causes of biodiversity changes (IPBES, 2019). This page presents a brief overview of the impacts of each factor on biodiversity, with emphasis on São Tomé and Príncipe.

Biodiversity and terrestrial and coastal ecosystems, including forests, terrestrial ecosystems in STP have been exposed to human changes for centuries, associated with its history of human occupation. The agricultural plantations introduced in the Portuguese colonial system led to the conversion of much of the islands' primary forests to the production of sugar cane, cocoa and coffee, in addition to bananas and maize, subsistence crops and cash crops. Most of the várzea forest and part of the forest in mountainous areas have been cleared in the northern and eastern areas of São Tomé island.

On this page we will present the most recent surveys of the main direct factors arising from human activities that today significantly threaten biodiversity and terrestrial ecosystems.

Category

Urgência Atual Níveis de Urgência (B-M-A)

Current Urgency Levels of Urgency (B-M-A)

Threat / direct driver of loss and impact

1. Land use change and habitat loss

A

Habitat loss due to large-scale infrastructure developments

A

Loss of inhabited large-scale agricultural developments

M A

Forest, mangrove and savannah habitat loss for smallholder farmers

M - A

Loss of sea turtle nesting beaches due to sand exploitation

M - A

Habitat loss due to urbanization and associated infrastructure, especially in coastal and rural areas

2.Use of natural resources and over exploitation

A

Forest degradation due to illegal selective logging: logging

A

Forest degradation due to unsustainable illegal selective logging and illegal selective wood production: wood for making charcoal

M

Unsustainable NTFP Exploitation

M - A

Hunting and searching for wild animals

M

Disturbances due to human presence in the forest

3. Pollution

M

Impacts of pesticides on freshwater species

4. 4-Invasive Exetic species

M

Evidence for EEI animals and plants. No evidence yet for systemic and predation impacts, however these can be considered, with risks to spp. of birds CR.

5. Climate Changes

B

Expected impacts on biodiversity and ecosystems, management for resilience

1-Land use change and habitat loss
1.1 Habitat loss due to large-scale infrastructure developments

This is one of the large-scale threats that can have transformative and devastating impacts on key ecosystems if not addressed and managed properly. This type of threat results from large-scale, discrete and unique land conversions promoted or endorsed by government decision-makers and has the potential to cause:

  • Habitat fragmentation: Building infrastructure fragments natural habitat into smaller pieces, isolating plant and animal populations. This hampers the movement, gene flow and dispersal of species, leading to a reduction in genetic diversity and increasing the risk of local extinction.
  • Direct Habitat Disposal: Infrastructure development involves the removal of entire natural habitats, resulting in the direct loss of plants, animals and other organisms that depend on these ecosystems for survival. Species adapted to specific habitats may not be able to adapt to modified environments and may disappear completely.
  • Impacts on Threatened Species: Often, habitats affected by infrastructure development are already home to threatened or endangered species. Habitat loss further aggravates the situation of these species, increasing their vulnerability and putting them at greater risk of extinction.
  • Changes in ecological balance: Ecosystems are complex interconnected systems in which each species plays an important role. Habitat loss can disrupt these interactions, leading to changes in the ecological balance, such as decreased pollination, decreased natural pest predators, and altered availability of food resources.
  • Loss of ecosystem services: Healthy ecosystems provide essential services to humans, such as climate regulation, water purification, crop pollination, and soil fertility. Habitat loss diminishes the ability of ecosystems to provide these services, undermining sustainability and human well-being.

Some examples of current known risks in STP are:
  • Construction of highways,
  • Development of tourist infrastructure,
  • Construction of dams and mini-hydro

1.2 Loss of forest habitat due to conversion to agriculture

Deforestation in STP peaked in the early 20th century, driven by the expansion of cash crop plantations (coffee, cocoa), many of which were later abandoned after the country gained independence in the 1970s, creating most of of today's secondary forest. More recently, the granting of new agricultural concessions and the expansion of small-scale agriculture (agriculture and agroforestry, for subsistence and local markets) has led to renewed levels of deforestation - of secondary forests and valuable forests, including areas of high conservation value. (HCV), including significant areas in the PNOST buffer zones. This is done in hopes of bringing back abandoned agricultural plantations to rehabilitate the harvesting industry, however the spread of small-scale agriculture increasingly illegally encroaching on forest public lands and PNOST is also a result of a antiquated land tenure regime, as well as poor land use planning and surveillance.

On Príncipe island, recent deforestation due to land conversion has been limited and largely confined to the north of the island.

For São Tomé, the map below shows the deforestation that occurred between 2009 and 2013, with the different sources of impact. The estimated average annual rate of deforestation on the island for the period 2009-2013 was 0.5%.

Habitat loss of forests, mangroves and savannahs for smallholder agriculture
This is a growing threat mainly linked to human population growth, including in rural areas. Impacts are more gradual and dispersed than in the case of land conversions by large agricultural concessions, but also more difficult to manage due to the large number of stakeholders involved and their fragmentation.
The small-scale agriculture that leads to real deforestation is especially for crops such as pepper and vanilla and horticulture at mid-altitudes in central São Tomé, offering suitable climatic conditions, grown largely after tree cover is removed. The low-intensity agroforestry areas around the PNOST are being increasingly cleaned in the most accessible areas of the island, such as in the center of Bom Sucesso. This release is encouraged by investment in transportation infrastructure and increased market opportunities for agricultural products.
An additional pressure is the conversion of forests by farmers who plant crops in agroforestry systems; this is less visible on satellite images or maps of deforestation because some tree cover is maintained but actually affects a much larger area that has not been adequately quantified recently.
STP's flail habitats are threatened by historic conversion to arable land, overharvesting of firewood and charcoal.
On a smaller scale, the (anthropogenic) savannah area in northern ST has seen forest loss and habitat degradation caused by slash-and-burn practices (widely used in this part of the island for the production of maize and sugarcane). sugar by family farming), composed of charcoal production
1.3 Loss of sea turtle nesting beaches due to sand extraction
The extraction of sand and rolled stones from beaches for construction purposes causes the destruction of beaches with potential for tourism or that represent areas for creation of. The resulting coastal erosion is also heavily affecting São Tomé, leading to the destruction of coastal infrastructure such as roads and avenues. In addition, this threat brings with it other potential impacts, such as:
  • Nesting Habitat Loss: Beaches are critical habitats for sea turtles to lay their eggs. Excessive extraction of sand from beaches can directly destroy or compromise these nesting sites. Sea turtles depend on beaches not only to lay eggs, but also for their young to hatch and make their journey to the ocean. The loss of nesting beaches can lead to a drastic decrease in the reproduction and survival of these species.
  •  
    Difficulty accessing the nesting site: The removal of large amounts of sand can change the topography of the beach, making it less suitable for sea turtles to climb to the nesting site. This can make it difficult for turtles to reach the beach, further reducing the chances of successful reproduction.
  •  
    Increased vulnerability of nests: Sand extraction can result in steeper and more unstable beaches, which increases the risk of coastal erosion. This exposes sea turtle nests to hazards such as flooding, storms and erosion, which can destroy or harm the eggs and hatchlings.
  •  
    Loss of genetic diversity: The loss of nesting beaches limits the availability of places for sea turtles to lay their eggs. This can lead to concentration of nests on fewer beaches, which increases the risk of inbreeding and reduces genetic diversity in sea turtle populations.
  •  
    Ripple effect on coastal biodiversity: Sea turtles play an important role in coastal ecosystems. They help control jellyfish populations, for example, which can proliferate without natural predators. The loss of sea turtles due to the destruction of nesting beaches can have negative effects on the entire food chain and the overall health of the coastal ecosystem.
1.4 Habitat loss due to urbanization and related infrastructure, especially in coastal and rural areas
Urbanization in rural and coastal areas and related infrastructure are spreading out of control, especially in São Tomé, causing direct and indirect impacts on natural ecosystems, affecting forests, coastal habitats, including mangroves and beaches that are most often sea turtle nesting beaches. This is a result of STP's human population growth, but also weaknesses in land use planning, surveillance, and law enforcement.
Some ways this habitat loss affects biodiversity:

Conversion of natural areas into urban areas: Urbanization involves the conversion of natural areas, such as forests, wetlands, savannahs and other ecosystems, into urban areas with buildings and human infrastructure. This results in direct habitat destruction and the loss of species that depend on these ecosystems to survive. The expansion of urban areas usually occurs in areas with high biological diversity, increasing the impact on the species present.
  • Habitat Fragmentation: Urbanization fragments natural habitat into smaller, isolated fragments separated by roads, buildings and other infrastructure. This disrupts ecological connectivity, making it difficult for species to move and disperse. Habitat fragmentation can lead to loss of genetic diversity, isolation of populations and increased risk of local extinction.
  • Specific Habitat Loss: Several species depend on specific habitats such as wetlands, mangroves, coastal dunes and agricultural rural areas. Urbanization and related infrastructure can destroy these habitats, leaving species without suitable places to live, reproduce and obtain resources. This results in population declines and eventually can lead to local extinction or total species extinction.
  • Alteration of ecological balance: Urbanization and associated infrastructure can cause significant changes in the ecological balance of affected areas. Removal of natural habitats can affect interspecies interactions, such as insect pollination of plants, predation, and seed dispersal by animals. These changes can lead to ecological imbalances, negatively impacting biodiversity and ecosystem functionality.
  • Indirect impacts: In addition to direct habitat loss, urbanization and related infrastructure also have indirect impacts on biodiversity. These include air and water pollution, the introduction of invasive species, additional fragmentation caused by roads and fences, and the disturbance and frightening of sensitive species by noise and human presence
Therefore, habitat loss due to urbanization and related infrastructure is a serious threat to terrestrial biodiversity, as it results in habitat destruction, fragmentation, loss of specific species and disruption of ecosystems. The conservation of remaining natural areas, the adoption of sustainable urban development practices and the protection of critical habitats are essential to mitigate these impacts and preserve biological diversity.
2-Use and over-exploitation of natural resources
2.1 Forest degradation due to unsustainable and illegal selective logging
This is another big major threat that can cause transformative impacts on key ecosystems, if not properly addressed and managed. Selective logging for construction purposes (mainly houses, given that 80% of houses in STP are made of wood; and for furniture and boats; there is no export of wood) and wood to produce charcoal for local use or sale are the two main. determining factors of forest degradation in STP - although there are important differences between the two islands. In some areas, forest degradation has progressed far enough to be classified as deforestation.

Forest degradation is difficult to capture by remote sensing and there is only limited quantitative data, the most recent forest inventory dating from 1999. However, sufficient information is available to indicate that this threat must be urgently managed.
The wood and charcoal value chains are different and impact forests in different ways and places. Stakeholders and especially response mechanisms differ between the two. These two value chains and drivers of forest degradation are therefore described separately below.

a) Extraction of original wood for construction purposes
Between 1989 and 1999, the interval between the two existing national forest inventories, there was an increase in the total volume of all species (which can be explained by secondary forest growth) and even a decrease in the volume of commercial species in c. 196,000 m3 (that is, an average annual decrease of around 19,600 m3) resulting from the increase in the consumption of sawn wood and its derivatives. Although this data is out of date, it illustrates the trend regarding wood needs in STP. According to the later study by Espírito & al. (2015), the pressure on forest resources increased even more, noting a sharp drop in the commercial volume of standing wood.
Returning to the current situation, logging in Príncipe is mostly compatible with licensing issues and the pressure is not yet critical (noting that the severity of impacts is not quantified). In São Tomé, on the other hand, most of these activities (80-95%) are unlicensed and illegal, and exploitation is poorly controlled and unsustainable. In 2014, the Directorate of Forests authorized the cutting of 1,452 trees in Príncipe (where illegal logging is rare) - and just 1,269 trees in São Tomé, which shows how poorly controlled logging is in ST.
There is a clear trend towards a sharp drop in the commercial volume of standing timber along slopes of intensive land use. A trend that applies to higher quality wood species, with almost no existing volume outside native and secondary forests. In shade plantation, the small volume of wood is almost entirely composed of low quality wood and, in non-forest lands, almost no wood persists. Also changes in the market for lower quality wood suggest that stocks of better quality wood are running out, with families and traders agreeing that the situation is bad (do Espírito et al., 2015).
The number of tree species driven for timber (c. 17) is limited compared to the overall species richness of the country's forests (350+ spp.). However, shifts to lower quality wood tend to broaden the spectrum of target species.
Species such as Azeitona and Viro are essential for ecosystem health and provide important ecosystem services (do Espírito, 2015). In addition, several species of conservation concern are affected, namely “the redwood tree” Staudtia pterocarpa, endemic to São Tomé and classified as Vulnerable by the IUCN Red List, and Carapa gogo and Santiria sp., which are endemic to São Tomé. and for STP, respectively, but have not yet been formally described and, as such, have not yet been evaluated by the IUCN. It is also noteworthy that Milicia excelsa, the species that is by far the most used, is classified as Near Threatened and that the also frequently used Cedrela odorata is vulnerable despite having been introduced to São Tomé.
The following maps show the current prevalence of logging on the islands of São Tomé and Príncipe. You can see how the activities are concentrated around and within the buffer zones, but also extend to the actual NPs. This is an indicator that there are no valuable resources left outside the PN and ZT in other parts of the island. In São Tomé, logging is beginning to have an impact in areas within the PNOST, mainly on the northern border, where the forest is accessible and has better conditions.
Logging depends largely on access to roads reachable from the forest by trails, however it also affects the SW neighborhood of ST (where there is no coastal road) where timber is brought to shore to be transported by boat.
b) Registration for charcoal production
Logging for charcoal production is the other main driver of forest degradation in STP. According to the 2012 census of the National Institute of Statistics (INE, 2012), about 57.6% of the population uses firewood and/or charcoal as a source of energy. Charcoal is used extensively in urban areas that have less access to firewood, for grilling fish. FAO has provided an estimate of 8 tonnes of coal used in STP per year, but this figure appears to be too low.
Extraction is selective in the early stages, when resources are plentiful: Pentaclethra macrophylla, the native African oil bean (Moandi), is the species most sought after for the quality of its charcoal. It is still being sought after in Príncipe, although resources are dwindling. However, as resources dwindle, charcoal makers turn to other lower quality species, as in São Tomé, where the preferred Moandi has disappeared from the charcoal market. Charcoal production can utilize any woody vegetation. In this sense, charcoal production is more widespread than logging, can be done on agricultural plots where no wood species remain, and can have broader systemic impacts than logging, leading to deforestation in general. Charcoal production is also likely to be more opportunistic than logging.
Mangrove habitats are also lost due to overharvesting of charcoal and firewood.
The following maps show the current prevalence of charcoal production on the islands of São Tomé and Príncipe. It can be seen how activities in ST are spread over the whole area of the island, except for the central area of the NPs - in shade plantations, secondary forests and high quality forests. However, there are critical points in the North and South where the pressure on the forest areas close to the PN has become severe and where exploration approaches the central area of the PN.
 
 
2.2 Unsustainable exploitation of NTFP
Non-Timber Forest Products (NTFPs) are important resources for local communities. In STP, many NTFPs are part of the diet, others are used for income generation and for prevention and treatment of many diseases by traditional healers and have pharmaceutical values; some are ornamental and others are used for crafts. NTFP exploitation contributes to well-being and poverty reduction, especially in rural areas, especially for women who are key stakeholders in some NTFP value chains. Another aspect to emphasize is its physical and economic accessibility, even for people who do not have agricultural land or regular income (Biloso, 2008). However, there is a lack of studies on its real importance in the Santomean economy.
NTFP sustainably harvested is a typical sustainable livelihoods intervention, aimed at diversifying local income sources without harming forests. However, in many cases, the NTFP P is an open access resource – when exploitation quickly becomes unsustainable and contributes to increasing pressure on forests (Carvalho, 2013). NTFP collection also leads to unintended indirect impacts, most notably the spread of IAS plants and the disturbance of critical habitats for sensitive birds during the breeding season.
The main NTFPs explored in STP are the following:
  • Giant African Land Snail and Giant São Tomé and Príncipe Land Snail, see next section.
  •  
    Palm wine, the third most consumed beverage in São Tomé (and Príncipe). Harvested directly from palm trees, it is the main beverage in local communities, creating, in addition to the environmental threat, serious social issues. Agricultural growth is limited around palm trees; it is for this reason that few are present on agricultural plots and that most exploited trees occur mainly in secondary forests, outside or within conservation areas. The daily harvesting and maintenance of palm trees, with regeneration facilitated by collectors, play an important role in the expansion of palm trees within the forest and increasing encroachment on native forests.
  •  
    Wild and domesticated honey, a particularly interesting product economically, as there is national and international demand; Wild honey collection was a direct threat to the park, causing wild hives to decline. In Príncipe, this decreased significantly with the development of the bee project, initiated in the GEF5 funded Biodiversity project, extended and monitored through the CEPF funded project, led by the Príncipe Foundation; but it is still happening in and around the park. People cut the tree to access the beehives and burn them to avoid being stung by the bees (due to the lack of equipment against it). The training provided by the bee project reduced (but did not eliminate) this practice, providing equipment, training, locations and a partnership with HBD's Patience Roça to secure pots for the production and sale of honey.
  • The African Oil Bean pentaclethra macrophylla, from which the seeds are collected for export especially to Nigeria, with the volume of trade growing so much that most of the seeds are collected on the forest floor and there is almost no regeneration left of that tree - and that it also happens to be the most prized wood for traditional charcoal;
  • 'Aframomum danielli African cardamom, mainly for the preparation of one of the typical dishes of São Tomé and Príncipe, the' calulu ';
  • Cola Nut Cola acuminata, powerful stimulant consumed locally with palm wine, export market to Nigeria and Angola;
  • Guinean Ashanti Piper pepper, used locally for cooking and potential export product; a pilot initiative on the island of Príncipe, led by the NGO Oikos, within the scope of the ECOFAC6 project, aimed at developing the wild pepper value chain, with potential buyers already identified;
  • African fan palm Borassus aethiopicum, construction and crafts;
  • African breadfruit Treculia africana, traditional edible fruit (seeds are of particular interest due to their high nutritional value)
  • Medicinal and aromatic plants, mostly based on traditional knowledge, some of which are overused.
2.3 Hunting and gathering wild fauna
Decree-Law No. 1/2016 defines hunting as "any action aimed at chasing, capturing or killing a wild animal, as well as collecting eggs and destroying bird and reptile nests". Hunting activities are carried out all year round, regardless of the natural cycles of specific species.
Hunting on the island of São Tomé is carried out for three different purposes (Carvalho, 2015):
  • Subsistence hunting - predominantly in rural areas and aimed primarily at wild pigs;
  • Commercial hunting - practiced mainly by urban hunters who sell the product in bars, restaurants or to private consumers, targeting birds, monkeys and bats;
  • Sport hunting - practiced by members of the highest socioeconomic classes in STP, usually during holidays or weekends and targeting mainly birds, but also monkeys and bats.
STP's rural populations rely on wild and feral introduced animals for protein. Wild pigs and the introduced Mona monkey Cercophitecus mona are the main vertebrate source of wild meat consumed in São Tomé and Príncipe. These non-native species are widely hunted and represent a significant livelihood and income generation opportunity for rural populations. The second most hunted group of vertebrates are bats, which are widely consumed by rural populations, particularly the straw-colored bat Eidolon helvum NT and the Egyptian bat Rousettus aegyptiacus.
Hunting is a major threat to the Dwarf Ibis CR and the São Tomé Olive Pigeon EN due to their low population size and limited range. Other bird species hunted in large numbers and consumed as a delicacy include the bronze downed pigeon Columba malherbii NT, from São Tomé, and the São Tomé green pigeon, Treron sanctithomae EN, the African green pigeon from Príncipe Treron calvus ssp. virescens, Lemon Dove Aplopelia larvata ssp. simplex / principalis and Laughing Dove Spilopelia senegalensis LC.
The uncontrolled foraging of the Obô Giant Land Snail Archachatina bicarinata VU is a notable threat to this endemic species, considered a conservation priority. Threat management is difficult because it is similar to the West African Giant Land Snail Archachatina marginata, an invasive pest species that was introduced to the islands 30 years ago and has become the third most important source of protein in STP (after fish and beef wild pig) - a preliminary study found that it represented 46% of all protein consumed in a community (Carvalho et al., 2015). Research, awareness-raising activities, and concrete conservation actions are underway to protect the species, primarily through CEPF funding.[1]
[1] https://www.cepf.net/grants/grantee-projects/save-sao-tome-giant-snail-learning-and-teaching-preserve

3-Pollution

Pollution from chemical pesticides is a threat especially to freshwater biodiversity in the country's rivers, streams, and streams. They result from anti-malaria bed nets impregnated with pesticides and from agricultural (especially horticultural) fields where farmers apply pesticides with virtually no controls. There are growing calls to reduce or ban the use of pesticides, given the effects on human health. There has been a decrease in the fish Eleotris vittata and freshwater shrimp Sicydium bustamantei, which play an important role in the food security of rural communities.

4-Invasive exotic species
While there is no evidence that invasive alien species (IAS) have had any systemic impact on the ecology and diversity of STP ecosystems or have led to species extinctions as in other SIDS, they are a growing concern.
In terms of EEI animals, there are wild cats Felis silvestris, Black Rats Rattus rattus, African Civet Civettictis civetta and Least Weasel Mustela nivalis. Although civets and weasels have been observed to prefer plantations, rats and civets have colonized native forest or indeed forest edges and likely have a deleterious effect on birds and other vertebrate species. Predation of adults, juveniles and bird nests by the ISS can be a potential threat to all endangered species, in particular the Dwarf Ibis.
Introduced wild pigs affect the forest floor by disturbing the undergrowth, which reduces tree regeneration. This can also have a positive impact on the Ibis as it creates a potentially good habitat for food.
The Mona Monkey Cercopithecus mona is an exotic species, but not considered invasive, which affects forest vegetation through seed dispersal, including non-native plants.
The West African Giant Land Snail Archachatina marginata, introduced 30 years ago on the islands, is fully established in coastal areas and secondary forests of São Tomé and Príncipe. The species has started to expand into areas of native forest, which is strongly correlated with the decrease in the endemic UV of the Giant Obô Archachatina bicarinata (Conservation Status currently under review) and will also have impacts on other fauna and flora. Both species are collected for food, see above.
The expansion of invasive and exotic plants into native and secondary forests is an additional concern, especially in São Tomé, which has been exposed to more trade, inhabitants and agricultural transformation. The expansion of EEI plants causes increasingly dense vegetation in the understory, reducing, for example, the suitability of forest habitat for the endangered Dwarf Ibis and Fiscal Fiscal of São Tomé. The Missouri Botanical Garden (2010) has specially named the following species of concern:
  • Bamboo Common Bambusa Bambusa vulgaris - Originally from China and recognized as invasive in New Zealand, Cooks Islands, Fiji, Reunion Island and Jamaica. This evergreen herbaceous tree penetrates the forest, spreading along streams through vegetative reproduction from the rhizome, which is particularly effective. Removes native plants forming very dense monospecific groups. It is reported in the PNOST.
  • West Indian raspberry Rubus rosifolius - native to Australia and Asia and invasive in Hawaii, French Polynesia and New Caledonia. This thorny shrub is prized for its edible fruit, but it forms dense thickets that close off passes and compete with native trees for competition and overcrowding. It was introduced in the archipelago after 1906. It is currently very abundant in secondary shrubs, plantations and along roads where it multiplies vegetatively by suckers and sexually. It can occur in native forests if the vegetation is open. There is, therefore, a risk that the birds that consume its berries take the seeds to the high altitude forests of the archipelago, where this species would find a suitable habitat for its expansion. In Tahiti, this species can be observed up to 2200 m above sea level. It is reported in the PNOST.
  • Lantana Lantana camara - native to central and northern South America, naturalized in nearly 60 countries and invasive in Africa, China, New Caledonia, India, Australia, Dominican Republic etc. This horticultural crop is found in agricultural areas, coastal areas, in natural and planted forests, in ruderal areas and in humid areas. It is one of the 100 most troublesome species in the world. Their impacts are multiple: they form dense populations that reduce biodiversity, change the fire regime, reduce the productivity of agricultural areas, increase the risk of erosion and poison livestock. It is reported in the north of São Tomé.
  • Leaf of Blood of Herbst Iresine herbstii - This perennial herbaceous plant native to Brazil currently has no invasive status. In São Tomé, it can be observed along the paths of the PNOST and its rapid progress is worrying, as it forms very dense populations and competes mainly with the giant Begonia of São Tomé, emblem of the PNOST. In its area of origin, it has been found up to 2500 m above sea level. If it continues to progress in the Park, there is a risk that, when it reaches more open environments, conducive to its development, there will be an "explosion" in its distribution.
  • Mexican sunflower Tithonia diversifolia - native to Central America and invasive in the Pacific Islands (Hawaii, Cook Islands, Galapagos, Fiji, French Polynesia, New Caledonia), Australia, Reunion Island, southwest China and Nigeria. This stoloniferous perennial herbaceous plant, 2 to 3 m tall, is used in São Tomé as a ground cover between crops. The absence of pre-bimillennial inventories suggests that their introduction is very recent. Its highly invasive nature in other areas, its rapid clonal reproduction and high production of light seeds, its ability to grow at high altitudes (China up to 2000 m), its ability to colonize open forest areas and its ability to form dense areas that prevent the growth of young native plants is of concern to scientists as it is grown in the buffer zone. On the other hand, experience has shown that when man loses control, the consequences can be disastrous for agriculture, which seems to be the case in the Bom Sucesso area, adjacent to the main entrance to the PNOST.
5-Climate changes
Like many other small island states, São Tomé and Príncipe is highly exposed and vulnerable to the impacts of climate change, such as rising sea levels and extreme weather events. Water resources, infrastructure, health and food security, and coastal protection will all be affected. Most livelihoods are highly dependent on limited natural resources and climate-sensitive activities, ie agriculture and forestry (crop production, shade planting, livestock, forest resources) and fisheries. Ever-increasing and increasingly competing demands for food, energy and space are accelerating the degradation of natural resources and ecosystems, which reduces their resilience to climate change. This situation increases the vulnerability of smallholders and creates a vicious cycle of low adaptive capacity, poverty, further degradation and hunger.
The threats identified to ecosystems by climate change are:
  • Accelerated soil erosion due to the very rugged nature of the islands.
  • Floods and subsequent degradation of forest areas in flat relief, such as shade forests located in the highlands.
  • Increase in the extension of the savannah zone in the northeast of the island of São Tomé, which is already suffering degradation due to the indiscriminate cutting of trees and bushes to produce charcoal.
  • Growing trend of average annual temperature values and decrease in rainfall.
  • Loss of forest cover due to landslides, as around 90% of the forests are located in high relief regions.
  • Reduction of forest area in case of prolonged drought, mainly shade forests and secondary forests.
  • Proliferation of pests and diseases in forest ecosystems.
  • Local extinction of animal and plant taxa (which will imply global extinction of endemic taxa)
  • Loss of plant and animal (insect) biomass
  • Reduction of soil water content, especially in black and brown clays and savannah soils that are already exposed to water scarcity.
  • Sea level rise & extreme events, loss of sea turtle nesting beaches.
  • Changing hydrology and coastal erosion, increasing with forest degradation and illegal/uncontrolled logging.
There is at least anecdotal evidence that weather patterns have begun to change, with temperatures rising and rainy seasons shorter, leading to reduced water flow in mountain streams. However, there is no evidence to date of any changes in ecological communities that could be linked to climate change.
The biggest national challenge is to integrate climate change into the national planning process and prepare quick and effective responses with the affected socio-economic sectors. With regard to the forestry sector, there is a consensus on plans and strategies for the sustainable development and management of forests and agroforestry ecosystems by 2030. However, experiments with species that adapt to changes in soil and climate conditions should be encouraged .
São Tomé, 26 de Julho de 2023