Oceans and Marine Ecosystems Facing Collapse
Our oceans are home to a staggering amount of life on our planet and play a critical role in the world’s natural systems, like regulating our climate, absorbing carbon dioxide and producing oxygen. They provide livelihoods and an important source of nutrition to billions of people across the planet. Without oceans there is no life as we know it. According to a study published in Science, less than 4% of the oceans remain unaffected by human activity. With a multitude of threats present, scientists are predicting at current rates a dramatic demise of 90% of our natural reefs by 2050. Oceans and reefs are at the forefront of climate change – the canaries in the coal mine and could be one of the first major ecosystems to be devastated by human activity.
The Intergovernmental Panel on Climate Change predicts at current rates of human activity global temperatures could rise between 1.4° C and 5.8° C by the end of the century. Global sea levels may rise by as much as 69 cm during the next 100 years, according to the statistics shown by WWF. Fast warming seas dramatically effect marine ecosystems which are incredibly sensitive to small increases in temperature and can cause an El Niño effect leading to widespread bleaching of coral reefs. Increasing frequency of tropical storms and hurricanes due to climate change also devastate reef systems.
Since the beginning of the industrial revolution in the early 1800s new research has discovered that massive amounts of CO2 introduced into the seas is altering the water chemistry and affecting the life cycles of many marine organisms, particularly those at the lower end of the food chain. Over the past 300 million years, ocean pH has been consistent however over the past two centuries a 25% increase in acidity has been documented. Eventually the effect could be that fish and other marine animals may find it harder to breathe as the dissolved oxygen essential for their life becomes difficult to extract as water becomes more acidic. A change in pH also prevents many species which rely on calcium carbonate to construct shells and build coral formations.
Overfishing has led to an alarming decline of certain fish species that are key parts in the ocean’s natural food chain. New industrial fishing methods have the ability to devastate fish stocks beyond recovery. Bottom trawling and dynamite fishing are the land equivalent of razing a forest to the ground. 76% of the world’s fisheries are already fully exploited or overfished. The removal of herbivorous fish, which normally graze on algae, is causing an abundance of algal blooms, which in turn transforms the ocean substrates eventually smothering and destroying natural marine habitats and coral reefs.
80% of all tourism takes place in coastal areas, with beaches and coral reefs amongst the most popular destinations. Exposure to high volumes of visitors causes damage from increases in marine traffic and human interaction with fragile species which often causes indirect physical damage by touching or colliding with reef systems.
Marine pollution is the spreading of harmful substances such as oil, plastic, industrial and agricultural waste and chemicals in to the ocean. On average humans use over 300 million tonnes of new plastic every year and half is only used once. 8 tonnes of plastic waste finds its way into the ocean annually. Over years the plastic breaks into tiny pieces, so much now that in some places plastic particles outnumber plankton by 26:1.
Marine species suffer directly from plastic pollution, 90% of sea birds have plastic in their stomachs. Plastic attracts toxic chemicals released from industry and agriculture and so the concentration of toxins increases as it moves up the food chain. Entry of plastic toxins into the human food chain is a concern and have been suggested to contribute to some cancers, infertility and behavioral disorders. Recently microplastics have come to the forefront of concern, small particles and fragments, typically less than 5mm in size, are split into primary and secondary classes. Primary microplastics are small pellets produced as base material for plastic production and added to cosmetic products and industrial cleaning machines. Secondary microplastics arise from the breakdown of larger plastic waste (carrier bags, fishing equipment or ‘ghost gear’, food packaging, fibres from clothes) and accumulate into huge zones entangling sea creatures. Fish ingest the waste mistaking them for prey and filter feeders ingest them alongside food particles.
Oil (liquid petroleum hydrocarbon) enters the ocean from oil spills, routine shipping, run offs and dumping. About 12% of oil in the ocean is directly from oil spills. Oil directly affects the water repellency of bird feathers and destroys the insulating ability of fur-bearing animals exposing them to the harsh elements of the environment and the creatures often die from hypothermia. Another example of marine pollution is run off from agricultural waste and products. Pesticides are toxic to water systems however fertilizers are not directly toxic but their presence in water alters the nutrient and species composition of an ecosystem. Eutrophication is a rapid growth of algae from an excess of nutrients, this depletes the dissolved oxygen concentration and in turn fish and aquatic life die from hypoxia.
Causes of habitat loss include development (buildings, foreshores, marinas, roads and bridges, reclamation for aquaculture), vegetation (mangrove) removal and logging, dredging, bottom trawling and ship groundings, destructive fishing technique (dynamite and small meshed nets) and anchoring. Costal areas close to human population centers are suffering most adverse effects from habitat loss, mainly from manmade stresses, and thus has far reaching impacts on the entire ocean biodiversity. Critical areas such as wetlands, mangroves and estuaries are breeding grounds for nearly all marine species. Wetlands are dredged to accommodate urban and industrial developments constructing marinas, ports and harbors. Dams decrease natural nutrient water and salinity and alter fish migration routes. Deforestation creates erosion and runoff of silt decreasing light penetrating water. Tourism activities affect ecosystems by directly damaging coral reefs with boats, anchors and divers as well as indirectly from land development, souvenir shells and corals, seafood and mangrove and coral lime used in construction. The loss of inshore coral reefs and costal mangroves adds to the damage causing sea levels to rise around 1mm per year which habitats cannot adapt to.
Mangrove forests are now one of the worlds most threatened tropical ecosystems with more than 35% of the worlds mangroves already lost, in some regions cleared faster than the rate of rain forests. When mangrove, sea grass and salt marsh habitats are destroyed they are no longer able to sequester carbon dioxide from the environment and large amounts are emitted back into the atmosphere.