What is our future?
We live on a blue planet; the world’s oceans cover three quarters of the Earth. They contain 97% of the Earth’s water and are currently absorbing around a third of the CO2 being produced by our activities and so helping in part by acting a buffer for some of the impacts of climate change. (30 to 40% of the carbon dioxide from human activity released into the atmosphere dissolves into oceans, resulting in the creation of carbonic acid.) Ocean acidification is therefore a rising concern. The average pH balance is dropping and as a result the growth of calcifying organisms such as corals and shellfish is being reduced. Acidification alone, though, is not the only pollution problem faced by the world’s seas, and others are escalating at an even faster rate. The impacts and implications are huge and growing.
Around 80% of marine pollution comes from land-based activities. Waste runs or is dumped into drains and rivers and hence the seas. Oil, fertilisers, sewage, plastics and toxic chemicals are all part of the mix. Oil spills are less frequent but in many countries without an established recycling system, used oil is thrown down the drain or poured directly into rivers. Nutrients in fertiliser runoff from farms and lawns produce algae, depleting dissolved oxygen and suffocating marine life, causing dead zones in places such as the Gulf of Mexico and the Baltic. In many regions, untreated sewage still flows into the seas – 80% of urban sewage discharged into the Mediterranean is untreated. A recent addition to the challenge is the role of desalination plants, cropping up in areas of water stress from the Middle East to Australia and California. As a core by-product of their water purification process, they add salt into the seas, so increasing salinity and hence acute toxicity.
While all of the pollutants are having severe negative impact, perhaps the most visible – hence one that will drive the biggest change in the next decade – is plastic. Around 275 million tons of plastic waste is generated each year around the world; between 4.8 million and 12.7 million tons is either washed or dumped deliberately into the sea. The World Bank expects the planet’s municipal solid waste to double within 15 years, much of this in the form of single-use plastic items. Bottles, bags, balloons, packaging, shoes – all take decades to break down. This waste is ingested by pretty much every marine animal including fish, dolphins, seals and turtles. So far, plastic has been found to be blocking the digestive tracts of at least 267 different species.