What are seaweed forests?
Seaweed forests are groups of seaweed and seagrass in the ocean.
Seaweed forests are the spawning grounds, nursery grounds and feeding grounds for many marine creatures such as abalone, turban shells, sea urchins, cuttlefish, groupers and dugongs. Not only are they important for marine biodiversity, but they are also essential for the fisheries that Japanese people depend on for our livelihoods.
Seaweeds are plants, which absorb carbon dioxide (CO2) from seawater, using light for photosynthesis and release oxygen into the seawater.
They also absorb nutrients necessary for growth and clean the water in the process.
As such, seaweed forests play a major role in creating an environment in which many creatures can survive. The oxygen produced by seaweed forests are also important for us terrestrial creatures, and the COXNUMX absorbed through photosynthesis enters the seawater from the atmosphere.
In Japan, seaweed forests are roughly consisted of (XNUMX) seaweeds, such as Sargassum, Eisenia bicyclis, Ecklonia cava and Kelp families, which grow on rocks, and (XNUMX) seagrass including Zostera, which grow on sandy soil. Translated with www.DeepL.com/Translator (free version)
Seaweed Denudation (Isoyake)
Distribution of prefectures where seagrass beds have been confirmed to decrease (2015) Created based on the Fisheries Agency's "Isoyake Guidelines"
The oceans are suffering. The seaweed forests are fast disappearing from the coasts around the world.
This is called seaweed denudation.
In Japan, the loss of seaweed forests is partly caused by sea urchins that overpopulate the shorelines and herbivorous fish that stay active and hungry for longer due to higher sea water temperature.
Due to seaweed denudation, the biodiversity of marine life becomes depleted, leading to serious consequences in the coastal fishing industry.
In some parts of the world, sea otters used to play an important role in protecting seaweed forests that they inhabit as they prey on the sea urchins. In Japan, where only a small number of sea otters remain in the wild, seaweed denudation is prevented by fishers who catch sea urchins.
However, because there are too many sea urchins and not enough seaweed to sustain them, the sea urchins are not of high enough quality to sell, which means that the fishers no longer want to catch them in some regions.
As sea urchins can live for over 10 years, seaweed denudation can continue for a long time. Now, in many regions, seaweed denudation is so severe that it cannot naturally return to the healthy state without human action.
In Japan, Fisheries Agency officially encourages fishers to take action to tackle seaweed denudation, with its published report ‘Seaweed Denudation Guideline’
Currently, many fishermen, diving shops and grassroots groups are taking action to tackle this long-term problem.
If the seagrass beds disappear, the diversity of marine organisms that the seagrass beds conserve will be impaired, which will have a serious impact on coastal fisheries such as abalone and turban shells.
As well as being significant part of the marine ecosystem, seaweed forests are also as effective as rainforests in sequestering carbon dioxide from the atmosphere.
The carbon dioxide absorbed by the trees and forests on land is referred to as green carbon, while that absorbed by seaweed, mangrove, phytoplankton, and other ecosystems of the ocean are called blue carbon, as named by UNEP (United Nations Environment Programme) - Blue carbon has been gaining attention in recent years.
In Japan, with its long coastlines, the seaweed forests of the coast are, without a doubt, contributing to absorption of blue carbon.
If seaweed denudation worsens,
invaluable ability for sequestering carbon dioxide is also lost.
As the levels of carbon dioxide in the atmosphere increase, temperatures soar as a result of the greenhouse effect - causing climate crisis.