What are Blue Forests?
Blue forests are a common name for vegetation in the ocean and tidal zones such as kelp and rockweed, seagrass, saltmarshes, and mangroves. These different “forests” have significant value because of the vital role they have within marine environments.
Why are they important?
Many marine species are dependent upon blue forests. These coastal vegetation ecosystems provide key nursery habitats, feeding grounds and refuge spaces for juvenile marine species and fish, as well as larger species who rely on blue forests for feeding.
Nutrients that contribute to turbidity, or the clouding of the ocean water, are absorbed by blue forests which increases water quality and fosters below-water photosynthesis processes for other marine plant species. Blue forests also bind sediments, preventing coastal erosion along coastlines, and protect from storm surges – both vital for coastal and small island communities that are frequently impacted by severe weather events.
Blue forests are also important for carbon dioxide (CO2) uptake and carbon storage – a process which is called “blue carbon”. The total biomass of blue forests take up less than 0.5% of the world’s ocean surface, yet it is estimated that they account for 70% of carbon storage in the ocean.
In this context, blue forests can play an important role in reducing the impacts of climate change. Conservation, restoration and the sustainable management of coastal areas are essential for reducing the global climate footprint and maintaining biological diversity.
What Ecosystem services do Blue Forest provide?
The ecosystem services provided by blue forests can be categorised as supporting (i.e., nutrient cycling and maintaining ecosystem functions), provisioning (i.e., providing food and resources), regulating (i.e., purifying water, storing carbon, and protecting coastlines), and cultural (i.e., aesthetics, recreation, and education). Thus, blue forests have economic value through tourism and other applications such as edible products for humans and animals, medicines, and thickening agents for cosmetics and foods.
The world from a blue forest perspective
Blue forests are an important nature-based solution to the climate and environmental crisis. They provide a range of essential ecosystem services, including carbon sequestration, biodiversity preservation, habitats and food for fish, and coastal protection.
Sustainably cultivated and harvested kelp can be used to reduce the climate and environmental footprint of our food, fertiliser and fuel.
The Big Five of Blue Forests
Rockweed
Rockweed is a macroalgae, and all rockweed species belong within the brown algae group (just as kelp do). Some of he most important rockweed species are spiral wrack (Fucus spiralis), serrated wrack (Fucus serratus), knotted wrack (Ascophyllum nodosum), bladderwrack (Fucus vesiculosus), channelled wrack (Pelvetia canaliculat) and of course, the Japanese species like Japanese wireweed (Sargassum muticum).
Historically, rockweed and kelp have been harvested and utilised in many ways. Algae are exceptionally nutritious, as they contain high amounts of iodine, calcium, and several essential vitamins. Algae also contain high amounts of protein, carbohydrates, and antioxidants. Because of their nutritional value, algae have traditionally been used as fertiliser for farming and agriculture in Norway. Macroalgae can also be harvested for feed production within the aquaculture industry.
Rockweed and kelp were traditionally also burned to make glass and produce iodine. More recently, a useful substance called alginate is often extracted from macroalgae, where it is used in the food and pharmaceutical industries. In addition, macroalgae are harvested for feed production for the aquaculture industry.
Seagrass
Seagrass is a terrestrial plant that migrated into the ocean 145 million years ago, and it is one of the few marine plants that flowers and has roots. Seagrass flowers under water and it is pollinated by other plants via ocean current. There is also evidence that small shrimp pollinate seagrasses much like how bees pollinate terrestrial plants. Seagrass propagates through rhizomes, where several plants are often connected by the same root system. This root system keeps the soft seabed stable, and protects coastlines against erosion in many places.
Seagrass absorbs carbon dioxide (CO2) from ocean water to form new plant tissue and produce large amounts of biomass in sealgrass beds. Some of the biomass is eaten by marine animals while the rest becomes mixed into sediments on the ocean floor. Seagrass beds can capture and store carbon in sediments 40% faster than terrestrial tropical forests
The carbon dioxide absorbed by seagrass also contributes to the maintaining of a stable pH in ocean waters. Too high a concentration of CO2 in the ocean results in ocean acidification, which affects marine organisms like crustaceans, mussels, and corals by the pH dissolving lime (calcium oxide) – an important element for shells and exoskeletons.
Seagrass is also the perfect nursery and refuge area for juvenile fish and shellfish that require safe and stable surroundings. Seagrass provides ideal habitats for eels as well and its are also a food source for swans in particular, who dive down to feed on the nutritious grass and then fertilise it through their droppings.
Salt marshes
Salt marshes are coastal wetlands that are flooded and drained by tidal water, and they are one of the most productive environments on Earth. Salt marshes do not host a wide diversity of plant species due to the high salinity of the ecosystem, but the species who do live in salt marshes are rare and well-adapted to these conditions. Salt-tolerant grasses and low shrubs are among some of the species found in salt marshes.
Over thousands of years, these salt-tolerant plants have built up layers of organic material forming peat – the same process that occurs in other marshlands. Peat contains large quantities of carbon and provides nourishment to the plants living above the peat layer.
Marshlands consists of several plant species that provide important habitats for both aquatic and terrestrial organisms, who use this ecosystem as a refuge from predators or as a breeding and spawning area. The abundance of food and their safe surroundings also make saltmarshes an ideal place for countless bird species.
Salt marshes dissipate wave energy by reducing the height of waves by almost 20%. The ecosystem can therefore reduce the effects of both floods and erosion along coasts. Marshes can also remove excess nutrients, microbes and pollutants by filtering water from rivers and other water sources. This protects nearby estuaries and coastal waters from the harmful effects of various environmental toxins.
Internationally, marshland is often used for agriculture. The nutrient-rich soil, or peat, is drained then the land is repurposed for anthropogenic purposes, particularly coastal development. The peat in saltmarshes has also historically been used as fuel in many countries.
Salt marshes and wetlands are protected in several countries due to their great value to the ecosystem and humans. In addition, the large amounts of carbon in the peat have meant that several countries are protecting wetland areas as measures against and adaptation to climate change. The protection of such areas therefore benefits both humans and nature.
Mangroves
Mangroves are shrubs and trees that grow in coastal waters. Mangroves are halophytes, meaning they are salt-tolerant trees that thrive in intertidal conditions. These diverse and productive ecosystems provide essential habitats for species, coastal protection from storms, and livelihood opportunities for coastal communities.
There are approximately 70 species of mangroves world-wide, of which there are six primary species: red mangroves (Rhizophora mangle), black mangroves (Avicennia germinans), white mangroves (Laguncularia racemosa), palm mangroves (Nypa fruticans), and mangrove apple (Sonneratia caseolaris).
Mangrove forests are only found in tropical and subtropical coastal zones around the world, as they do not tolerate freezing temperatures. However, mangroves have adapted to grow in a range of different coastal ecosystems. For example, red mangroves are predominantly found bordering coastlines where they face more direct impact from wave intensity and storm surge, necessitating more substantial submerged roots to keep them in place and more aerial roots to provide the trees with oxygen through thick mud. Black mangroves are also coastal, though often located higher up along the coastline, while white mangroves can sit at even higher coastal elevations and do not generally have any visible aerial roots.
Mangroves are the most productive carbon-storing blue forests ecosystem. They store carbon through above-ground tree biomass and below-ground roots and soil. Coastal nations around the world are increasingly incorporating mangrove carbon – and blue carbon more generally – into climate mitigation goals through Nationally Determined Contributions (NDCs) under the United Nations Framework Convention on Climate Change (UNFCCC).
Because their carbon stocks can be reliably measured and monitored, mangrove forests are also ideal for blue carbon offsetting initiatives. Additionally, mangroves provide nursery habitats, areas of refuge, and feeding grounds for many juvenile tropical fish species, shellfish, crustaceans and invertebrates. Terrestrial species benefit from mangrove ecosystems as well, with migratory birds, mammals and reptiles reliant on mangrove forests for breeding sites and feeding grounds.
Due to their complex root system, mangroves also absorb wave energy and stay in place through the rise and fall of daily tides. In this way, mangroves play a crucial role in protecting shorelines from coastal erosion and storm surge. Because they often border freshwater rivers and oceans, mangroves also trap and store sediments and pollutants which helps prevent nitrates and phosphates from flowing into the sea.
Mangrove forests are one of the most threatened habitats around the world, with global mangrove populations declining by 1% annually – approximately 150,000 hectares per year. Mangroves are predominately threatened by anthropogenic activity. Deforestation rates of mangroves can be attributed to large-scale shrimp aquaculture, agriculture (namely palm oil plantations and rice paddies), coastal development, pollution, and the harvest of mangrove wood for fuel and building materials.
When mangrove ecosystems become degraded from deforestation, the carbon once stored in their biomass is released back into the atmosphere, thus negating the carbon-storing benefits they naturally possess.
Kelp
Kelp are large, brown algae seaweeds that are found in the shallow outer region of coastal zones. Kelp can grow up to four meters high. Kelp do not reproduce by seeds and pollination like terrestrial plants do, but instead they contain microscopic spores. These spores are released, then they attach to the seabed and grow into male and female plants. When the male plant has fertilised the female plant, new spores are released. Other species of kelp can multiply by parts of the blade breaking off and attaching to the seabed to grow a new individual.
Kelp grow similarly to trees in a forest by creating 3-dimensional structures underwater that provide unique habitats, refuges, and nurseries for diverse groups of marine organisms.
Kelp forests grow in shallow, rocky habitats in most temperate coastal areas in northern latitudes of the world. They cover 25% of the world’s coastline and much of the Norwegian coast. Norwegian kelp forests in particular make up a large part of the total areas of blue forests in Europe.
Unlike plants, macroalgae do not have roots. Instead, they have holdfasts that are used to attach to rocks and other hard substrate. Kelp do not grow further than where the sun’s rays reach because they photosynthesise. Therefore, kelp thrive best when growing from 1 to 25 meters deep, which is slightly deeper than rockweed. In terms of wave energy, some species like tangle kelp can tolerate stronger waves, whereas sugar kelp prefer calmer waters.
Kelp forests form the basis of life for many marine species. Smaller algae often grow on kelp stalks and their underbrush, especially red algae. In addition to the algae, small crustaceans and molluscs thrive particularly well, as do fish who seek refuge within this blue forest. Molluscs, crustaceans and small fish also serve as food sources for larger animals such as seabirds, marine mammals, and larger fish. Thus, many species are drawn to this unique and diverse ecosystem.
Kelp forests form the basis of life for many marine species. Smaller algae often grow on kelp stalks and their underbrush, especially red algae. In addition to the algae, small crustaceans and molluscs thrive particularly well, as do fish who seek refuge within this blue forest. Molluscs, crustaceans and small fish also serve as food sources for larger animals such as seabirds, marine mammals, and larger fish. Thus, many species are drawn to this unique and diverse ecosystem.
Though kelp do not have roots, they still can capture carbon. Living kelp are considered short-term carbon sinks through the biomass they produce. This biomass is either eaten by other animals, or it breaks off to form detritus, which often drifts far from its original location before settling onto the seabed. Unlike living kelp, kelp detritus sequesters carbon for centuries once it becomes buried in seafloor sediment.
When harvested, kelp also provide other commodifiable provisioning services. Kelp can be transformed into thickening agents, cosmetics, medical dressings and supplements, plastic alternatives, edible products, and animal feed.
What is needed today:
Integrated management. Blue forests are affected by a number of risk factors, including nutrient run-off from land, coastal development, fisheries, aquaculture, and climate change. If we are going to better protect and restore these ecosystems, we must think and plan holistically.
Protection is preferable to restoration. We should protect the blue forest that we have, put in place the conditions necessary for lost blue forests to return on their own, and – if necessary – actively restore habitats.
Balance in the ecosystem. Many kelp forests in central and northern Norway have been replaced by the underwater deserts. Research points to overfishing in the 1970s as the cause. Without top predators, kelp-eating sea urchins have taken over. To hasten the return of kelp forests, the balance in these ecosystems must be restored. One solution is to harvest the empty sea urchins, fatten them up, and sell them as luxury seafood.
International cooperation. For example, Norway already supports blue forest projects through development, including mangrove forests in Indonesia as well as with knowledge exchange.
Cost-effective mapping and monitoring methods
Education and Awareness
