ASK A SCIENTIST
Question: How are the oceans being affected by global warming?
Over the past decade, scientists have come to the consensus that humanity is changing our world's climate in many ways. One of the biggest effects is called global warming: the 10 hottest years on record have all occurred since 1998.
What does this mean for the oceans? For starters, they're warming up too. This means that fish who are used to cooler water have to move deeper or towards the poles. For some species, like cod, a move like that means losing 20 to 50% of the population. Other species, like trout and tuna, can't move because they breed in specific locations, and may face extinction.
This is a huge problem for coral reefs, which can't move and take hundreds or thousands of years to grow. Coral reefs are `bleaching', or dying and turning white, at alarming rates. The Great Barrier Reef is projected to be 95% dead by 2050. Coral reefs provide homes to a quarter of all marine species.
Global warming also means that glaciers and polar ice caps are melting. Melting ice adds water to the oceans. This makes sea levels rise. Rising oceans are a problem for both humans and animals: rising oceans are predicted to engulf the entire Pacific island nation of the Maldives by 2050, and threaten many coastal areas around the world like Cape Cod. And deeper seas mean many plants and animals will have to move or adapt.
But there's another problem that humans are causing for the oceans. One big cause of climate change is the huge amount of carbon dioxide, or CO2, that humans are putting into the atmosphere. That CO2 doesn't just stay in the atmosphere. It gets absorbed by the oceans. Think about a bottle of soda pop, but in reverse: the bubbles are going INTO the water. The problem is that CO2 turns into carbonic acid in the oceans, and makes the oceans more acidic. Oceans are 30% more acidic now than they were in 1700, and they could become 150% more acidic by 2100.
Some fish are very sensitive to acid, and cannot survive in a more acidic ocean. Coral and shelled creatures don't grow as well with more acid: the acid prevents shell growth. Many species of plankton -- the main source of food for most fish -- cannot live in acidic water. If most plankton died, the marine food chain would be cut off at the base, affecting all ocean life.
In short, climate change is, well, changing the oceans: it's making them hotter, it's raising the sea level, and it's making it more acidic. All this means that fish and other plants and animals will have to adjust or move to survive, and many will not be able to. Every time one species can't adjust, everything that depends on it for food or shelter is affected too. It's one big dangerous domino effect.
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