Melting ice in the polar regions threatens to shut off a powerful natural engine that drives the ocean currents. It cycles water from the surface to the ocean floor over thousands of years.

Changes to this system - like temperature - could alter the entire physical system of the marine environment. It might trigger a 'domino effect' of marine ecosystem collapse around the world.

This same system also absorbs large amounts of carbon dioxide. Some believe it rivals large rainforests and the 'lungs of the earth'. If it is altered the effect may be to allow more carbon dioxide into the atmosphere. This will cause the earth to warm more.

All whales, dolphins and porpoises will be affected by these changes. For some food supply may decrease. For instance baleen whales may loose their primary food source - krill.

In some areas dolphin and porpoise habitat will change or be lost altogether. Coastal populations of dolphins could loose their reef systems supporting their food chain.

No-one knows what other long term impacts may occur as the temperature of the ocean change.

An increase in ultraviolet radiation in some areas of the world is thought the be threatening the base of the ocean the food-chain - krill.

These tiny crustaceans are the major food-source for many of the largest baleen whales who feed at the polar regions each year, migrating towards the equator to calve and breed.

As krill numbers drop these whales will loose their only food source and starvation will be inevitable.

Skin cancers also threaten light skinned whales and dolphins. In some areas of the world, the incidence of carcinomas (skin cancer) are increasing. Like humans, the potential for skin cancer from exposure to ultraviolet radiation grows every year.

Climate changes will probably cause the sea level to rise. Rising sea levels and water temperature threaten to destroy the coastal habitats in which many dolphins, porpoises and small whales depend for food and shelter.

Many coastal communities of dolphin and porpoises remain in limited areas over many generations. Coastal wetlands, mangroves, seagrass beds and reef systems are the landscapes of their homes. As the sea level rises many of these areas will die or be drastically changed.

Pollution is also destroying many of these areas. This is especially a problem around industrial centres and big coastal cities.

A growing number of rivers are being dammed and dolphins that live within these systems are becoming endangered.

Whales, dolphins and porpoises are vulnerable to the long-term effects of chemical pollution. Some of these pollutants are toxic and can cause death. Others chemicals cause diseases, destroy their environment or reduce their food supply.

Many pollutants accumulate in their body tissue while they feed. These toxins can remain in their body fats over their whole life. The species most at risk are those that feed high on the food-chain, eating longer lived predatory fish. These are the same group animals found most commonly along our coastlines.

In the first weeks of feeding large quantities of these pollutants are passed to calves through their mother's milk. In some populations of dolphins it has become common for the first born calf to die very young from this toxic load.

The main source of this pollution comes from industrial and human waste, storm water and dumping chemicals or from the run-off of chemicals used in agriculture.

Illegal dumping of waste at sea also increase the pollutants in the ocean system. Oil spills and discharges from ships still occur around the world. Some areas of the ocean act as 'sinks' for some of the more persistent and damaging compounds such PCB, Mercury, Cadmium, Lead and Zinc.

All whales, dolphins and porpoises are dependent on their ability to make and hear sound for communication. They are very sensitive sound under water. They also use sound to tell them where they are. Interference with this ability threatens their survival.

Loud damaging noise is made by military sonar or the detonations used in seismic testing.

Some of these sounds can travel over 100km and can stress, disorientate or cause physical harm. This is a far more threatening form of pollution for whales and dolphins than previously believed.

A number of recent studies have linked 'strandings' to low frequency seismic and industrial noise. Some underwater blasts can have enough impact to cause haemorrhages in lungs and sinuses. The impacts of seismic blasts could kill animals that were too close.

Another form of noise pollution originates from fishing vessels, offshore drilling platforms and ships. The most problematic vessel sounds come from the large ships that create low frequency 'thumps' that are in the hearing range of the large baleen whales.

Fishing nets, packaging straps, nylon ropes, loops of cotton cord, plastic bags and fishing line all pose hazards for coastal dolphins.

Offshore drift nets still kill thousands of dolphins each year.

Getting tangled or swallowing these plastics is becoming more common in many populations of coastal dolphins. It can kill or severely disfigure these animals.

Humans haven't learnt to share the sea very well. Destructive fishing gear is still widely used and as many as 250,000 dolphin die each year in association with the world-wide fishing industry.

Driftnets are still used around the world. The rope used to make the nets is not easily detected by whales and dolphins who innocently swim into them and become tangled. Often called 'the walls of death' these long deep nets kill thousands of dolphins and whales each year.In many part of the world dolphins are deliberately targeted by fishers because they show fisheries where large school of fish might be. The dolphins in these cases are usually killed.

In other parts of the world dolphins are hunted for meat because fish supplies are decreasing. This is often because the waters have become polluted or are overfished.

Other fishing boats accidentally catch dolphins in their nets and on their lines but these animals usually drown before they can be released. Some fishers still believe that dolphins are competing with them for fish and take action to destroy them.

Some large coastal aquaculture operations are also catching and killing many dolphins each year. The animals become tangled in the hanging nets while trying to catch food attracted to the pen because of the artificial feeds.

Many whales and dolphins live in the open sea. They often come across many of our ocean activities. In some part of the world, where shipping lanes are busy, ships regularly hit surfacing or sleeping whales. These hits can kill or seriously injure the animals.

It is so much better to see whales in the wild. Whales and dolphins supposedly performing tricks for us in aquariums have been torn from their natural environment, from their families, are deprived of communication with their own kind and sentenced to a lifetime of confinement.

The capture industry often defends itself for research purposes and because they rescue 'stranded' animals. Stranded animals should be returned to the ocean, not put in captivity. In reality many animals are deliberately caught and will die in captivity.

While many boat and plane operators act responsibly, some feel the pressure from unknowing customers to get closer to whales and dolphins than the animals may want. This can stress whales and dolphins while they are in their critical habitats to breed or calve.

Despite decades of campaigning the commercial whale hunt goes on under the guise of scientific whaling.

Hundreds of whales are still hunted each year. Thousands of dolphins are slaughtered and sold illegally as whale meat in a growing black market.

Many governments around the world are committed to a future with no whaling. Other pro-whaling nations continue to wage a war to keep whaling open at all costs.

In the 1980s, after many years of public outcry, an international moratorium from whaling was imposed by the International Whaling Commission (IWC).As some whale populations recover the moratorium is under threat by pro-whaling countries who want to see whaling open again.