What Harms Ocean Life?

Oceans seem too huge to harm, don't they? But we humans are actually making our oceans sick. They suffer from oil spills, overfishing, air pollution, heavy development along coastlines, tourist traffic, offshore oil and gas mining, destruction of coral reefs — the list goes on.

It usually takes a long time to see pollution's effects. For instance, it took years for scientists to realize that the insecticide DDT weakened the eggshells of peregrine falcons and other raptors so much that the young developed abnormally. At other times, we see the immediate effects of pollution through a catastrophe like the chemical factory accident in Bhopal, India, where more than 2,000 people died from breathing toxic fumes.

The biggest problems affecting ocean health are:

• pollution from land
• pollution from air
• ship and boat traffic
• overfishing
• global warming
• damage to coastlines

More than 75 percent of ocean pollution comes from human activity on land. Even if you live inland, you could be harming oceans. For example, rain could wash motor oil from your driveway into drains and eventually to sea.

• A recent study revealed that 500 billion litres of untreated sewage gushes into rivers, lakes, and seas every year from 20 major Canadian cities. This offal could form a smelly pile as long as the 7,800-kilometre Trans-Canada Highway and almost three storeys deep! Some scientists estimate that waste water accounts for half the world's ocean pollution from land. Besides excrement, raw sewage contains about 200 chemicals, grease, oil, paint thinner, plastic bags and other synthetics, gravel, rags, and hair.
• Our salt waters contain toxic chemicals from farms, industries, and homes. First, we dump chemicals into drains. Next, they flow (often untreated) into streams and rivers — and finally to the ocean. Most of these contaminants lurk for years along coastlines, harming wildlife and humans.
• Construction crews dredging harbours, rivers, and other waterways dump about 215 million tonnes of silt into oceans.
• Even military waste and nuclear-powered submarines end up on the ocean floor!
• We throw about 5.4 million tonnes of litter into the ocean every year.

In the Arctic, between December and April each year, you can see a haze in the air. It contains pollutants that have drifted mainly from Asia and Europe. Eventually, some of it falls with snow or rain to the land or sea.

• Some scientists think about 20 percent of all ocean pollution comes from the air.
• The wind can blow pollution from land thousands of kilometres out to sea.
• Airborne pollution includes dusts from soil, volcanoes, and forest fires, as well as poisonous sprays, gases, and emissions belching from industrial smokestacks.

There may be no roads on the ocean, but there is a lot of traffic. About 35,000 ships and 1.2 million large fishing boats sail the ocean blue. It's anybody's guess how many motorboats, dugouts, barges, hydrofoils, sailboats, junks, and other vessels also use the seas. Most of them pollute.

• Many ships and pleasure craft discharge sewage and other waste water into the ocean.
• Nearly half the oil in oceans comes from accidents and shipping activities.
• Ships spill more than oil. It took nearly eight months to clean up a 1985 spill off the coast of Somalia of a ship carrying 105 different chemicals — most of them poisonous.
• A worldwide $1.9 trillion travel industry contributes to ocean pollution through cruise ships, boat tours, and hotels too close to shore.
• Tonnes of plastic debris reach even isolated ocean spots. In 1985, people on ships around the world tossed at least 450,000 plastic containers into the ocean. Seabirds, turtles, seals, and dolphins slowly strangle, suffocate, or die when they get entangled in plastic six-pack rings from beer and pop cans, fishing lines, nets, kite string, and ropes. Giant leatherback turtles, which are endangered worldwide, mistake plastic bags and balloons for jellyfish. Once swallowed, the plastic clogs their intestines, and they die.

According to weather reports kept since the 1860s, the Earth is definitely warming up. Even a few degrees can mean big changes for the planet. For one thing, the oceans will get warmer. Because water expands when it warms, water will slowly cover land along the coasts. For small islands, or those only a few metres above sea level (such as many in the Pacific and Indian oceans), this change could mean serious trouble.

Here's how global warming works:

• People cause it, mostly by burning fossil fuels like oil and coal that power everything from televisions to cars.
• Fossil fuels give off several gases when burned, including carbon dioxide. These gases hold the sun's heat close to the Earth — as in a greenhouse. That's why it's called the greenhouse effect.
• The gases act a bit like greenhouse walls. They form part of the atmosphere, which wraps around the Earth like a blanket of air.
• Sunlight streams through the atmosphere to the planet. Then the gases hold the heat close to the Earth for a long time.
• Because we add lots of extra gases to the atmosphere, we may heat the Earth up too much.

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