“There is no pathway to any of our shared global goals that does not involve protecting and restoring nature, including the ocean, on an unprecedented scale,” said Zac Goldsmith, International Environment Minister, on Ocean Action Day during last year’s COP26.

For so long, ocean protection has been an ‘add on’ to terrestrial conservation and restoration efforts, but “restoring nature, including the ocean” needs to be stressed because traditional restoration efforts on a large scale have mainly focused away from marine environments.

Our seas have suffered from relentless overfishing, pollution, deoxygenation, and in recent decades have been impacted by climate change. Two thirds of the world’s fish stocks are either fished at their limit or overfished. Disruptions to food chains are also caused by plastic pollution, with an estimated 8 million tonnes of plastic waste entering our ocean every year.

Not only do rivers and water resources act as a highway that continuously feeds pollution into our oceans but acknowledging the dynamic relationship between terrestrial and marine systems is critical to any real approach to ocean protection.

Plastic Pollution

Rivers are considered the main vein by which plastic pollution is carried into our oceans. Nearly 80% of the estimated 5 trillion plastic particles in the world’s oceans is channelled by the world’s rivers with the rest coming directly from marine pollution (such as fishing nets).

Ocean plastic is particularly problematic because it acts as a magnet for toxic chemicals as they float around in our waters, accumulating in the food chain until they eventually end up on our plates at home and in restaurants.

However, the fact that ocean plastic mainly derives from our rivers is not communicated or publicly well-known. Instead, many efforts have focused on cleaning up costal communities and ocean plastic like the Great Pacific Garbage Patch. And while these efforts are important, it fails to address the source of the issue.

This is something that was identified early on in the history of The Ocean Cleanup, a nonprofit developing and scaling technologies to rid the oceans of plastic. Despite crowdfunding the largest sum of money in the platform's history by pledging to clean up ocean plastic, they quickly realised that developing methods of intercepting plastic and cleaning up rivers would make their long-term goal much easier. Since their inception, they have removed 1.3m kg of trash from our rivers and oceans.

With plastic pollution set to double over the next ten years, there is no doubt that successful ocean plastic cleanup requires a focus on the relationship between terrestrial and marine systems.

Chemical Pollution

While we haven’t yet measured the toxic pathways that result from plastic and chemical pollution mixing in groundwater, the chemicals in our river systems have been widely recognised and quantifiable for decades. It is estimated that over three quarters of all chemical pollution in our oceans derives from land. A toxic combination of pesticides, fertilisers, pharmaceutical residues, sewage discharge, and other dangerous industrial pollutants over decades have directly caused the degradation of marine and coastal environments across the world.

Chemical pollution is particularly dangerous for ecosystem health. Through the increased availability of chemicals in the water, algal blooms can grow to such an extent that they exhaust water of all available oxygen thereby causing ‘dead zones.’ It’s believed that there are over 400 dead zones in our oceans right now, most famously at the mouth of the Mississippi river, which covers around 6,000 square miles.

The relationships between land-based chemical pollution and coastal ecosystem health have been well understood for decades, yet efforts to curb pollution have often been unsuccessful.

Research from Queensland found pesticide regulation proved incapable of preventing ongoing pollution adversely affecting the Great Barrier Reef, which is already suffering from repeated warm water events that cause coral bleaching and putting the reef under tremendous stress. However, new and innovative solutions that recognise land-sea connections are showing promise, including ‘Reef Credits’.

Reef Credits are market-based instruments that allows land managers to carry out water quality improvement projects in the Great Barrier Reef catchment. The idea is that by providing purchasable credits to the public and private sector, land managers are financially incentivised to reduce the chemical run off flowing into the Great Barrier Reef ecosystem.

This type of marked-based solution is essential for the future of marine health.

Climate Change

Finally, climate change, mainly driven by atmospheric pollution from terrestrial systems, threatens to accelerate marine ecosystem degradation over the next century.

One of the starkest impacts of climate change is the increase in warm water events, which has damaged coral reefs worldwide and resulted in ‘coral bleaching’ (the removal of algae from the coral). As one of our most biodiverse ecosystems in the world, providing not only food and shelter for a vast array of species, coral reefs provide a number of ecosystem services to people and is a foundation of the blue economy.

Yet, research has shown how human-driven changes on land disrupts other foundational aspects of our oceans. Changes in coastal forest cover has been shown to cause a chain reaction that reduces marine algae and plankton abundance in the neighbouring marine environment, termed ‘long ecological interaction chains.’ As the foundation of marine food webs, alterations to algae and plankton abundance can have cascading impacts on marine food chains.

In addition, research has indicated how people in West Africa harvest wild terrestrial fauna more intensely in years when marine fauna is in short supply. Marine fauna is a key resource for income and protein, so when availability is reduced, it becomes a huge stressor on West African households. Bushmeat often becomes the alternative, to the detriment of over 40 species of terrestrial fauna in West Africa, which contributes to the multibillion-dollar bushmeat trade that is among the greatest threats to tropical wildlife.

Evidently, the delicate balance between natural marine and terrestrial resources is still being surfaced in research worldwide.

No matter the source of pollution (physical, chemical, or atmospheric), it is vital for effective ocean programming to remain adaptive and have the capacity to react to the growing scientific understanding of the complex relationships between terrestrial and marine systems.

There is no doubt that the close relationship between land and ocean pollution has eroded some of the systemic resilience of communities and marine environments worldwide. The terrestrial-marine relationship cannot be ignored when improving livelihoods globally. With increasing focus on the interconnections between these systems, benefits and recovery can be enhanced for communities that straddle the coastal-marine nexus.

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