- Some examples
- Alteration of fisheries & consequences
- Degradation of coastal ecosystems & impacts
- Climate change: causes and consequences
- Limits of international law and conventions to protect the ocean
Marine activities such as mining operations, shipping, fishing, cruise liners introduce large quantities of toxic substances, into the ocean. Oil spills are largely confined to navigation corridors where they pollute beaches and harm fish, shellfish and bird population. But most of the waste and pollution that reaches the oceans is produced on land. Fertilizers and pesticides from farms, oil from streets and driveways, sewage water and trash from cities, make their way through the watershed into rivers and ultimately into the ocean. Another important land-based source is emission in the atmosphere from industry or transport… Once emitted many chemical compounds (copper, nickel, mercury, cadmium, lead zinc and synthetic organic compounds) stay in the air for weeks or more and this is the major route by which they reach the oceans, travelling with the winds. All these pollutants are then redistributed around the world by marine currents and can have impacts far from their source of emission.
Pollution of the oceans results in physical and ecological changes and/or damages and impacts health of marine species. Eutrophication is caused by excess nutrients, such as nitrogen and phosphorus, being washed into the sea from farmland and with sewage, causing the overproduction of algae. When the algae die, the bacteria that decompose their remains use much of the oxygen dissolved in the water, leading to the death of other organisms, including fish. Pollutions have impact on humans by causing health problems (linked to bathing or consumption of sea food), economics losses (living resources inappropriate for consumption, decreasing benefits linked to tourism, increasing of the costs linked to health problems, coastal management, social problems…).
Alteration of fisheries & consequences
Overfishing is one of the largest threats to the health of the world’s oceans. For decades the world’s commercial fishing fleets have been taking unsustainable amounts of fish and marine life, to the extent that many fish stocks are now declining or even collapsing. Limited capacity of reconstitution of the wild populations makes it difficult to restore the stocks. Other problems are linked with aquaculture: abusive use of wild fish to feed the raised species, pollution and biological invasion.
The living resources of the sea suffer also from pollution; habitat alteration and destruction; non-sustainable and destructive fishing techniques (trawling, use of poisons, etc) and global climate change. Tourism (sportfishing, diving, trade of “souvenirs” made with endangered species…) and captures of wild species for aquariology are also threats to living resources and marine biodiversity.
Now at a peak, catches have fallen slightly, despite continuing growth in the size of the world’s fishing fleet. The decline in fish stocks in the northern hemisphere has resulted in an exodus of big fishing fleets to the relatively less exploited waters of the South. One net result of this has been the demise of small-scale artisanal fishers and a drain of resources from the poor South to the rich North.
The consequences of drop of fisheries are multiple: economical, social and environmental like threatened food security of societies heavily dependent on fish; loss of biological resources; loss of biodiversity; health problems (due to poisoned seafood); starvation and unemployment.
Degradation of coastal ecosystems & impacts
It is on coastal ecosystems that human impact is the most important. Human activities inducing environmental problems on coastlines are increasing with the density of population on coasts: coastal construction and development (urbanization, facilities for tourism, ports…), inland activities (agriculture, deforestation, industrialization, dams on rivers…), overexploitation of coastal living resources, and tourism impact.
The more people on coastal areas, the more pressure they impose both on land and sea. This has resulted in increased domestic and industrial effluent, more areas of landfill and erosion of coastlines due to infrastructure construction and coastal development. Natural landscapes and habitats are altered, overwhelmed and destroyed. Pollution alters life conditions; provokes loss of biodiversity, alteration of food chains and of all marine ecosystems.
Lagoons and coastal waters are ‘reclaimed’, reefs are damaged by fishing or tourism, wetlands are drained, the floodplains around estuaries are built over and reduced, mangroves are cut down for wood or aquaculture. Fish stocks, fresh water, soils and beach sands are often overexploited. The consequences are : loss of food resources especially in developing countries ; water access problem ; health problems ; social and economic impact linked to a loss of benefits and employment (fishing industry, tourism, increasing costs of coastal management); etc…
Climate change: causes and consequences
Today, scientists observe a consistent raise of the global average temperature of Earth’s atmosphere. They agree that this phenomenon is linked with higher atmospheric concentrations of greenhouse gases because of human activities. The primary human-related causes of CO2 release are fossil fuel combustion (mainly oil, coal and gas) and deforestation.
Even a moderate continued temperature rise causes melting of ice caps and glaciers, alteration of coastlines, modification of currents flows… The consequences are rising sea levels (mainly because the oceans will expand as they warm up), shifting weather patterns and an increase in the frequency of extreme weather events. Scientists expect massive traumas both for human populations and for nature. Species both in the ocean and on land will have to adapt, migrate or disappear. Ecosystems will be completely modified. For humanity, possible consequences are: modification of water resources, people displaced to avoid flooding of their cities or villages, loss of land and natural resources on coastline, impact on agriculture and fisheries (food security), impact on human health (development of diseases), damage or destruction of infrastructures built on the coastline (cities, industries, port installation, tourist accommodations…), increased pollution consequently to flooding and destruction of infrastructure. The social, economical and environmental consequences will be incalculable.
Limits of international law and conventions to protect the ocean
The Exclusive Economic Zone or EEZ refers to the coastal waters that lie adjacent to the coast and extend 200 nautical miles offshore. They are under the jurisdictions and control of the adjacent country. The 10 Largest Territorial Powers (with the biggest sea claims) are USA, France, Australia, Russia, Canada, China, Brazil, Indonesia, India and New Zealand. The rest of the oceans, or high waters, are free to be exploited by all countries under constraints of UN Convention on the Law of the Sea. A large number of political initiatives took place during the last decade but most of them have difficulties to respond to their goals and are not being implemented in a coordinated way. The lack of political will and means of control are the first reasons for this. Most developing countries are also under economic and social stress and are forced to give a relatively low priority to protecting the environment and conserving natural resources even though this might undermine their long-term sustainable development.