Sea 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.

Threats to marine life and ecosystems refers to hazards that negatively affect the biodiversity and health of the oceans. Pollution, climate change, overfishing, destruction of coastal habitats, invasive species, ocean acidification and collisions with vessels are some of the main threats. Here we will present the most recent surveys of the main human activities that compromise marine ecosystems, causing damage to organisms and imbalances in the food chain in the marine ecosystems of the islands.

It is essential to take action to preserve marine life and ocean sustainability, ensuring a healthy future for our marine ecosystems.


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

Threat / direct driver of loss and impact

1. Habitat Loss


Limited evidence, but impacts can be expected from dynamite fishing and specific sites due to harbor construction and possible sedimentation

2. Use of natural resources and over exploitation


Unsustainable and harmful fishing and related impacts


Sea turtles: capture, egg collection and associated capture


Disorganized exploitation of coastal aggregates

3. Pollution

M - A

Chemical pollution, including pesticides in rivers and urban waste shipments.

M - A

Plastic pollution


Sound Pollution from navigation and seismic activities


Pollution with hydrocarbons from oil and gas exploration, which has not yet started

4. Invasive exotic species


No registration yet

5. Climate Change


Expected impacts on fish stocks and marine food web, management for resilience

Table 1-overview of direct drivers of ecosystem and marine biodiversity losses
1-Habitat Loss

There is currently no evidence of notable loss of marine habitat in STP. Coastal construction affecting actual marine habitats is limited, but harbor construction and sedimentation may have had local impacts. Some fishing techniques are known to cause habitat degradation and loss, mainly bottom trawling and dynamite fishing. As dynamite fishing is still being practiced in STP, it can be assumed that there are impacts. There are no reports of impacts by bottom trawlers. As corals in STP do not build reefs, there are only limited impacts from traditional line and net fishing. Sand extraction is negatively affecting beach habitats and therefore the biggest threat to sea turtle reproduction, see below; but this is counted as a threat in the terrestrial biodiversity section, because the management response falls within terrestrial intervention mandates.

2-The use and over-exploitation of natural resources
2.1 Unsustainable and harmful fishing and related impacts

Fishing at unsustainable levels and the use of harmful practices (eg dynamite fishing, non-selective gear, spearfishing) have led to local declines in fisheries (especially demersal) resources, with avalanche effects on the food chain and marine ecosystems. In Príncipe, 67% of the 355 fishermen and traders surveyed perceived a decline in total fish catches over the last 10 years, suggesting significant changes in marine ecosystems. With declining resources (especially of the more valuable species such as the Atlantic Wreckfish (Cherne) Polyprion americanus), local artisanal fishermen are now traveling further and further, often without fishing boats and safety equipment, risking their lives. In São Tomé, fishing is very intense in the northern part of the island due to the concentration of populations and proximity to the capital, and fishermen are now seeing more and more in the rich waters of the south. According to recent research, 70% of all fishermen who actively exploit the southern fishing grounds reside in communities located on the north coast of São Tomé. Fishermen from São Tomé are also increasingly traveling to the less explored waters around Príncipe and to the surrounding islets, including Ilhas Tinhosas, which will be proclaimed a marine PA in the future -, which generates conflict between the fishermen of the two islands.


In São Tomé and Príncipe, 15% of the working population is involved in artisanal fishing and more than 30,000 people indirectly benefit from the fishing sector. Coastal communities essentially depend on fishery resources for animal protein consumption and income generation. A gradual decline in fish abundance and the increasing use of non-adaptive fishing techniques are increasing threats to the main source of protein for the island's population. Today, overfishing and habitat degradation are negatively impacting the viability of fisheries livelihoods on both islands. As a result, fishers are resorting to illegal harvesting of wild animals and/or unsustainable fishing practices.


The threat of unsustainable artisanal fishing is compounded by foreign industrial trawlers operating in STP's EEZ. Some of them operate under bilateral agreements with the government of STP, but these and others are unlicensed and involved in IUU fishing. AIS systems are in place and should have been put in place in 2018, but overall the government's ability to patrol and enforce its marine area is limited.


In addition, there is a growing whale and dolphin watching industry that can do harm if not properly regulated and monitored. In addition, cetaceans and sea turtles are captured accidentally as bycatch.

2.2 Sea turtles: capture, egg collection and bycatch

Sea turtles are traditionally exploited for human consumption in STP, with adult turtles killed for their meat and eggs to be collected from nesting beaches - with adult sea turtles captured indiscriminately using hooks, harpoons and gill nets in front of the main nesting beaches around the island (Castroviejo et al. 1994). Additionally, some sea turtle by-products are used for traditional medicinal purposes; noting that in STP sea turtles are not used in religious ceremonies, as in some West African countries. The manufacture of crafts (mainly jewelry) from its shell was the biggest driver of the indiscriminate harvesting of the hawksbill (CR) turtle in the past, especially in the 1990s. Until recently, it was common to find sea turtle jewelry on the streets and in São Tomé stores for sale to unknown tourists, but these products are hard to find in local markets today. However, local artisans reported trade with Angola.


Despite the enactment of a national law in 2014 to protect sea turtles, the decline in fish abundance and the increasing demand for animal protein (linked to human population growth) has encouraged local communities to target even more sea turtles than they traditionally have. .


In 2003, the local NGO MARAPA (Sea, Environment and Artisanal Fishing) created the Tatô Program with the aim of protecting sea turtles. For years, MARAPA had the support of several national and international organizations, mainly the EU in the previous phases of the ECOFAC project. In 2018, the Associação Tatô Program was created to give this program more sustainability, thus maintaining the name, already known by all communities, national authorities and civil society. The association encourages community rangers to monitor and record any kind of suspicious activity to capture sea turtles or eggs on nesting beaches. With the efforts made in the last 4-5 years, illegal catches have been reduced by a factor of 10 in São Tomé. However, the threat remains strong in the northern part of the island, in the communities between Morro Peixe and Micoló (Programa Tatô, 2019; Praia Gamboa, Neves and Santa Catarina), so these practices continue to represent an important threat to sea turtles in STP. Poaching eggs for subsistence remains a common practice in local communities and a variety of animals, including crabs, rats, dogs and pigs, also destroy eggs and hatchlings. Similar interventions are being carried out on the island of Príncipe, through the Príncipe Foundation.


Furthermore, sand extraction is negatively affecting beach habitats and therefore the main threat to sea turtle reproduction; but this is counted as a threat in the terrestrial biodiversity section, because the management response falls within terrestrial intervention mandates.

2.3 Disorganized exploitation of coastal aggregates

Refers to the indiscriminate and unplanned extraction of non-metallic (inert) mineral resources from the country's coastal areas. This activity, often carried out without considering the environmental and social impacts, can result in serious damage to coastal ecosystems, marine biodiversity and the quality of life of local communities.

The extraction of coastal aggregates involves the removal of sand and other materials from beaches, dunes and seabed for use in civil construction, in the manufacture of concrete and in other sectors. However, because it is done in a disorganized way, this activity has contributed to coastal erosion, habitat degradation, loss of biodiversity, changing the dynamics of marine currents and even and is jeopardizing the safety of coastal communities. In addition, they are also important causes of the destruction of sea turtle breeding areas.


The pollution of rivers carrying pesticides and emissions of liquid urban waste is a major threat to marine ecosystems in STP. There are reports that the application of pesticides to combat malaria has harmed marine life (corals) in at least parts of São Tomé.

Plastic pollution (plastic bags and items, fishing lines and nets, micro plastics) from land-based sources, as well as cargo and fishing boats, is becoming an emerging problem affecting sea turtles and cetaceans. It could potentially affect the entire marine food chain, but there is no evidence yet.

Noise pollution from marine and seismic surveys linked to oil and gas exploration is transforming the marine soundscape and there is growing concern about possible impacts on marine fauna (Compton et al. 2008; Hatch and Wright 2007), Lavender et al. 2014; Weir and Dolman 2007).

The early start of oil & gas exploration in STP's territorial waters can also cause pollution, both through continuous emissions from deep-water wells and accidents. This is not a threat at this stage, but there have been cases of tankers cleaning their tanks in STP waters.

4-Invasive exotic species

There are still no reports or evidence for the presence or impacts of marine IAS, but this could be due to a lack of relevant research.

5-Climate Changes

Climate change is expected to have major impacts on fish stocks affecting reproduction, stock distribution ranges and migration patterns. Given that STP is heavily dependent on fisheries resources for food security, as explained above, impacts could be severe unless fisheries and marine ecosystems are managed for resilience - which will require management of stocks, marine ecosystems and conservation, in addition to reducing other stressors such as disturbance and pollution.