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When you think of a forest, chances are you picture trees rising high above you, leaves crunching underfoot. But there are some very different types of forest - in and under the water -  that are just as beautiful and just as precious. While they don’t all contain trees, these so-called blue forests are essential to life on this planet, say experts.

“They protect our coastlines from flooding and erosion. They shelter wildlife and provide sustainable livelihoods for communities. And we’re just beginning to understand how important blue forests are in keeping our planet's climate stable,” says Leticia Carvalho, United Nations Environment Programme’s (UNEP’s) Head of Marine and Freshwater Ecosystems. “But they are also highly vulnerable. We need to cherish and protect these vital resources.”

In 2021, UNEP’s partners - the Norwegian Blue Forests Network- hosted a free online presentation on how to protect and revive these ecosystems. Here’s a look at five of the most important blue forests.

1. Mangroves

Mangroves are salt-tolerant trees and shrubs which grow along coasts. They support a rich biodiversity and provide a nursery for fish and crustaceans. Mangroves also act as a form of natural coastal defence against storm surges, tsunamis, rising sea levels and erosion.

UNEP research shows that mangrove ecosystems underpin local economies by supporting fisheries, providing other food sources and protecting coastlines. Every hectare of mangrove forest represents an estimated US$33–57,000 per year.  They also extract up to five times more carbon from the atmosphere than forests on land. 

Find out more about their role in climate change adaptation in this animation.

Yet, mangroves are disappearing three to five times faster than overall global forest losses. It is estimated that mangrove coverage has been halved in the past 40 years. In Kenya and Madagascar, UNEP is helping communities recognize the value of mangroves in carbon storage, coastal protection and livelihoods. Countries like Cuba and Pakistan have also pledged to protect and restore their mangrove forests.

2. Salt marshes

Salt marshes are found in bays and estuaries along tidal coastlines in parts of the world where there is low-lying land and a temperate climate. They are important nesting and feeding grounds for birds, and their shallow, brackish waters provide shelter for fish, molluscs and crustaceans.

Research shows that salt marshes, together with mangroves, peatlands and seagrass beds, store more carbon than all the world’s on-land forests combined.

3. Seagrass meadows

Seagrasses are marine flowering plants found in shallow waters from the tropics to the Arctic Circle. Seagrass meadows protect coasts from erosion, store carbon and contribute to food security by helping produce healthy fish stocks. A powerful nature-based solution to climate change, even though they cover only 0.1 per cent of the ocean floor, seagrasses store around 18 per cent of oceanic carbon. It has recently been discovered that they filter microplastics, helping keep our waters free from harmful pollution. But it is estimated that 7 per cent of seagrass habitat is being lost each year, equivalent to a football field every 30 minutes.

Find out more in this free ebook.

4. Rockweed

Rockweed comprises several species of macroalgae, recognizable by their air-filled bladders, which allow them to float upright at low tide. Although people have understood the value of rockweed for centuries – it is a staple food in some societies, and it is the original source of iodine – it is now being recognized as a sustainable resource with vast economic potential as part of the blue economy. Commercial ventures like rockweed farming can create new economic opportunities, particularly for women in rural communities.

5. Kelp forests

Kelp forests grow – sometimes as much as two feet in a day – in cold, clear waters. Pollution and over-fishing are threatening these ecosystems but like rockweed, their commercial value is being recognized as part of the sustainable blue economy. Kelp forests are now being sustainably harvested for use in medicine, food, industry, animal feed, and fertilizing farmland. Kelp and other species of algae do not need fertilizers to grow – just sunlight, carbon dioxide and water.