Tavishi adjusts her oxygen mask and dives into the sea. Soon, she tells herself, she will be gazing at the wonderful colours of the coral reef. But when she reaches it she stares in horror: the coral is a ghostly white - which means that it is very sick.

Coral reefs look like plants, but are actually made up of creatures related to sea anemonesSoft, brightly coloured sea creatures that look like flowers and often live on rocks under the water. and jellyfish. Some of these coral polyps are rough to the touch because they have a limestone skeleton called a calicle.

The polyps are usually found in groups known as colonies. When a large number of these join together a reef is formed.

Many types depend on tiny algaeA simple plant that grows in or on water. called zooxanthellae, which live in the colony and produce 90% of the food that allows the coral to grow. But a rise or fall in the ocean's temperature, or an increase in its acidity, can result in algae leaving a reef.

When that happens, the coral turns white and is left starved and vulnerableat risk of being harmed. This is bad news for the whole ocean, since 25% of all marine species live in coral.¹ 

The US National Oceanic and Atmospheric Administration has just reported a "mass coral bleaching event", which means that every ocean which contains coral is affected.

Bleaching can happen if the sea temperature rises by just 1C for a month. Unless the temperature drops back again within two months, the coral can die.

Reefs can recover, however, and scientists are trying various ways of helping them. One is to create giant tanks in which the polyps are encouraged to spawn. The spawn is then planted on endangered reefs.

The good news is that some corals are more resistant to heat than others. By breeding from these, scientists can increase a reef's chances of survival.

Another approach uses sound. Researchers have found that coral larvaeInsects in the next stage of development after they have emerged from eggs. A caterpillar is a larva. can be attracted to struggling reefs by using underwater speakers to broadcast the sound of healthy reefs, such as fish brushing against them.

Coral reefs are not the only life forms now benefitting from human care and ingenuity. In the Forest of DeanA geographical, historical and cultural region in the western part of the county of Gloucestershire, England., rope bridges have been put up to allow dormice to travel between treetops, crossing the gaps left where diseased ash trees have been felled. And Northumberland Zoo has approached the local fire service asking for old and unwanted equipment, which it hopes to make into hammocks, food hangers and toys for its animals.

But is there still hope for nature?

Yes: Some of the ideas people are using to help it are really amazing, and they are bringing real passion to the challenge. And reefs in certain parts of the world, such as Cambodia, are doing very well.

No: Humans have already done too much damage. The oceans are growing warmer all the time and the most industrialised nations are dragging their feet in the vital business of reducing carbon emissions.

Or... Nature is extraordinarily resilient, as the area around the Chernobyl nuclear disaster shows. Even if humanity destroys itself through climate change, other forms of life will survive.

Sea anemones - Soft, brightly coloured sea creatures that look like flowers and often live on rocks under the water.

Algae - A simple plant that grows in or on water.

vulnerable - at risk of being harmed

Larvae - Insects in the next stage of development after they have emerged from eggs. A caterpillar is a larva.

Forest of Dean - A geographical, historical and cultural region in the western part of the county of Gloucestershire, England.