The marine environment, nature’s solution to climate change
Professor Rick Stafford is based at Bournemouth University. He is part of the Nature-based Solutions content team for Climate Exp0.
While many people have seen the UK coastline from the beach, or on the news, there are only small groups of rockpoolers, divers and sea goers who have truly appreciated the marine life we have. Seals, dolphins, porpoises, whales and plankton-eating basking sharks can be spotted from the shore, or from local boat trips. Kelp beds, sponges, soft corals, brightly coloured fish, cuttlefish, crabs and lobsters are all common in UK waters, so on a calm day, diving off the UK coast can rival that of anywhere on the planet. Not only do marine environments showcase rich biodiversity, but they could be a key solution to climate change as they provide coastal protection and capture organic matter, locking it up in the sediment and preventing it becoming atmospheric carbon dioxide.
A nature-based solution (NbS) is a habitat or even a wider seascape that has the ability to boost biodiversity and provide other benefits, especially around carbon capture or adaptation to climate change. The recent report from the British Ecological Society has reviewed the NbS potential of many landscapes and seascapes to address the duel environmental threats of climate change and biodiversity loss. The sea and the coast are especially important.
Seagrass and saltmarsh habitats are perhaps the most well-known marine and coastal NbS. Vegetation grows in sediment rich organic material, and as the plants grow, they trap more and more organic, carbon rich material in the sediment. Being coastal habitats, seagrass and saltmarsh capture not only some carbon from plants as they decompose, but also organic matter from the land, floating down rivers and into the sea. By burying the carbon away from oxygen, it prevents carbon dioxide being produced and entering the atmosphere.
The sea is vast, covering over 70% of the Earth’s surface. While not as effective as seagrass or saltmarsh per unit area, most of the seabed is sediment (sand and mud), which traps huge amounts of organic carbon. Shallow areas of rock are also covered in seaweeds, such as rapidly growing kelp, vital for biodiversity and seafood such as crabs and lobsters. The majority of kelp is eaten by other marine life, but new research suggests around 5% gets incorporated into marine sediments, hence sequestered and prevented from forming carbon dioxide.
Large marine fauna also play a role in the ability of the ocean to capture carbon. Whales often feed in the deep sea, and rest (and defecate) at the surface. This creates a nutrient pump, bringing nitrates, phosphates and iron to the surface, where they boost phytoplankton growth. Phytoplankton are the biggest contributor to photosynthesis on the planet, so boosting growth means more CO2 is absorbed. As well as bringing nutrients to the surface, marine fauna can move carbon from the surface to depth (for example, as dead animals and faeces sink). There the pressure of the deep water keeps gasses like carbon dioxide safely dissolved. Finally, predatory fish (which includes almost any fish you are likely to eat) can help control the animal biomass in the sea, and therefore reduce the amount of carbon dioxide produced through respiration.
The majority of marine plants and animals have water dispersed planktonic stages, where eggs, spores or larvae will move in the ocean currents. Therefore, it is often the case that marine environments will recover if they are left alone, free from pressures such as fishing or pollution. Good marine management, including marine protected areas for vulnerable species and habitats, is vital to optimise marine nature-based solutions. Some habitats also benefit greatly from active restoration. Seagrass, and in the tropics, mangrove forests, are good examples, and recently many projects have been established to replace these lost habitats.
When it comes to sea-level rise leading to coastal flooding, allowing sea defences to be breached (known as managed realignment) can often be combined with creation of new saltmarsh habitats, creating protection from floods and storm surges, while also boosting biodiversity and capturing carbon.
In the UK, the seas are not currently in optimal condition. Historic overfishing, pollution, poor management and now climate change are all taking their toll. Despite recent recoveries, North Sea cod stocks are again classed as overfished, huge supertrawlers are fishing in our designated protected areas and invasive species become more common in our waters. Historically, the UK has lost up to 92% of seagrass beds through pollution and related disease. Considerable amounts of saltmarsh have also been lost, often through coastal squeeze, where retreating saltmarshes come up against human developments. Again, this will be a familiar picture of degraded marine ecosystems to many people, wherever they live in the world.
Protecting, creating and restoring habitats can help reduce carbon dioxide, boost biodiversity, and for coastal habitats, dissipate wave action associated with increased storms, preventing erosion and coastal flooding. A few simple calculations show that effective protection, and restoration of habitats such as seagrass and saltmarsh could potentially result in UK waters — a little over 750 thousand square kilometres — sequestering well over 2 million tonnes of CO2 every year, even before less certain calculations around the role of marine fauna are included. Globally, coupled with very strong emissions reductions, the ocean could sequester over half of the anthropogenic CO2 emissions produced each year.
The British Ecological Society report that to establish NbS on a national or international scale and achieve the full benefits, we need public support, strong multi-stakeholder and multi-level governance, industry involvement and finance, strong government and international leadership, and national and international state funding. As well as rewards in terms of biodiversity, carbon capture and climate change adaptation, such investment can also provide job opportunities to support a real green recovery– a win-win solution for land and sea.
Climate Exp0 is the first virtual conference from the COP26 Universities Network and the Italian University Network for Sustainable Development (RUS), sponsored by UK Research and Innovation (UKRI), Cambridge University Press, the Conference of Italian University Rectors (CRUI), and the 2021 UN Climate Change Summit (COP26).
Running from 17–21 May 2021, it takes place at a critical juncture in the COP26 pre-meetings and negotiations, and is part of the All4Climate Italy 2021 official pre-COP26 initiatives. Learn more and register your place via https://www.climateexp0.org.
