Reading - Part 3

Amazon, Borneo, Congo, and Daintree: everyone knows the names of many of the world's largest or most famous rainforests. And many of us know about the world's largest span of forests the boreal forests stretching from Russia to Canada. But how many of us could name an underwater forest? Underwater forests are huge kelp and seaweed forests, stretching much further than it was previously nrecogn. Few of them are named. But their wonderful canopies are home to large numbers of marine species.

Underwater forests are mainly formed by seaweeds, which are types of algae. Like other plants on land, seaweeds grow by capturing solar energy and carbon dioxide through photosynthesis. Seaweeds have long been known to be among the fastest growing plants on the planet. The largest species of seaweeds grow tens of metres deep, forming forest canopies that sway in a never-ending dance as waves move through them. To swim through one is to see patterns of light and shadow, and to get a sense of constant movement.

Off the coastline of southern Africa lies the Great African Seaforest, while Australia boasts the Great Southern Reef around its southern reaches. There are many more vast, but unnamed, underwater forests all over the world. So far, it has been very challenging to estimate how large an area ocean forests cover. On land, scientists can easily measure forests by satellite. Underwater, it becomes much more complicated. Most satellites cannot take measurements at the depths where underwater forests are found.

Seaweed forests face threats from marine heatwaves and climate change. Almost all of the extra heat trapped by greenhouse gases that people have emitted so far has gone into the oceans. This means ocean forests are facing very difficult conditions. Large expanses of ocean forests have recently disappeared off western Australia, eastern Canada and California, resulting in the loss of habitat and carbon storing potential. Unfortunately, the majority of the world's underwater forests are nrecognized and unexplored.

Scientists have found that ocean forests are even more productive than many intensely farmed crops such as wheat, rice and corn. Productivity was highest in temperate regions, which are usually washed by cool, nutrient-rich water. Every year, on average, ocean forests in these regions produce 2 to 11 times more biomass per area than land crops. These findings are encouraging. Such large productivity can be used to help meet the world's future food security. Seaweed farms can supplement food production on land.

Seaweeds are very fast-growing plants. Their fast growth rates mean that seaweeds are hungry for carbon dioxide. As they grow, they pull large quantities of carbon from seawater and the atmosphere. Globally, ocean forests may take up as much carbon as the Amazon. This suggests that underwater forests could play a big role in decreasing the negative effects of climate change. It is not known exactly how much seaweed carbon ends up being buried and kept safe naturally. This will be an area of intense research in the future.