What are marine forests?

Marine forests are biodiverse-rich ecosystems engineered by key structural taxa of macroalgae, seagrass and corals. Depending on the keystone taxa, we can separate them in three main ecosystems: seaweed banks, seagrass meadows and coral reefs.

Seagrass meadows

Seagrasses are marine flowering plants rooted to the seafloor. They can grow over large areas, creating extensive and dense underwater meadows. They usually colonize soft marine sediment in the presence of low or moderate wave energy and provide food and habitat to diverse marine life, comparable to that of coral reefs. Seagrass meadows are considered among the most productive ecosystems in the world.

Seaweed banks

Seaweeds are species of macroscopic multicellular marine algae, and there are thousands of them, some of which form impressive, dense underwater forests. For example, the well-known kelp is a seaweed that can create dense forests in temperate to cold waters. These forests can tower up to 45 meters from the sea floor, providing shelter, food and habitat to several marine species of all shapes and sizes, from seahorses to sharks and seals.

Coral reefs

Coral reefs are marine ecosystems characterized by reef-building corals, animal colonies composed of several identical coral polyps that build a common skeleton of different shapes and colours. They are considered the most biodiverse marine ecosystem in the world, estimated to harbour around 25% of all marine life. This is not hard to imagine once you see a photo of a vibrant and rich coral reef in bright turquoise waters. However, not all corals form exuberant and colourful shallow-water reefs in tropical coasts. There are also those that thrive down in the deep where light does not reach, with some living at depths down to 3000 meters. Unlike their shallow-water cousins, deep-sea corals do not require light as a source of nutrition, rather they feed on microscopic organisms that flow in ocean currents. Some deep-sea corals, such as gorgonians and black corals, can also form dense assemblages, creating a biodiversity hotspot where sunlight is dim or non-existent.

Why should we care?

While very different from each other in terms of the species they support, their geographic distribution, and the environmental conditions they need to thrive, these three ecosystems have more in common with each other than you might think. They are all extremely productive and biodiverse, serving as nursery and feeding grounds to many marine species, they provide coastal and sediment protection against erosion, and they are very important in counteracting climate change by sequestering carbon. Seagrass meadows, for example, occupy less than 0.2% of the area of the world’s oceans but are estimated to sequester around 10% of all the carbon buried in ocean sediment annually.

Unfortunately, there is something else they have in common, and that is that they are disappearing at unprecedented rates. It is estimated that the planet has lost half of its coral reefs since 1950 and at least close to 30% of seagrass meadows in the past century.

The disappearance of these environments can lead to environmental and humanitarian catastrophes. It will lead to increased coastal erosion, food depletion, and will affect costal activities that are dependent on these ecosystems. We will also lose the intrinsic value of such a biodiverse beauty. This is why it is imperative, now more than ever, to develop practices and tools to prevent further destruction, and when possible, restore, at least a part of what has been lost.

Left: Coral reef. Photo by Pedro Frade. Right: Researchers in a kelp forest

Marine forest restoration with RESTORESEAS

Despite massive scales of degradation, out of sight and challenging to reach, restoration of marine forests is rare. There have been growing efforts around the world, by local communities and organizations to restore these rich ecosystems, however, these are biologically and ecologically complex systems that require an interdisciplinary and strategic approach for efficient restoration at large scales. And that is where RESTORESEAS comes in.

RESTORESEAS is an international Biodiversa+ funded project, that brings together researchers from Europe, South America, and Africa to improve the resilience of marine forests’ restoration in the Atlantic coasts. It aims at proposing management practices for the conservation and restoration of marine forests that will account for keystone species, microbial partners and diseases, and key challenges of climate change.

It is becoming clear that without the support of local communities and the integration of eco-social approaches, conservation efforts can take longer to implement, and in some cases be hampered by other social needs. Taking that in consideration, RESTORESEAS also has a strong citizen science and educational component, which aims at implementing an education and communications strategy that integrates society in different aspects of marine forest restoration, while also demonstrating the importance of these ecosystems to the communities involved.

Coral restoration work. Left: Measuring a coral in-situ, photo by Christina Egger. Right: Incubation of coral fragments in a tank, so that they grow until they can be re-introduced back into the ocean, photo by Márcio Coelho.

Researchers at RESTORESEAS are aware that restoration should be the last resort. They know that we will never be able to replicate in just a couple of decades an ecosystem that took millions of years to grow and evolve. So, besides restoring the ecosystems that have been lost, RESTORESEAS also aims at determining areas of importance to conservation through predictive modelling and contact with relevant policy makers.

This project’s ultimate goal is one that is shared by many scientists, activists, organizations and politicians– to develop practical and applicable nature-based solutions that will lead to healthier marine ecosystems, and subsequently a healthier world.

Written by Maria Pinto, Natural History Museum Vienna