1.Discuss the role of marine carbon dioxide removal (mCDR) as a strategy to combat climate change. Highlight the potential, challenges, and significance of biotic and abiotic approaches in achieving global climate goals.
The ocean, the earth’s vast blue lung, has long played a critical but underappreciated role in moderating the planet’s climate. It has absorbed 25% of anthropogenic carbon dioxide emissions and more than 90% of the excess heat generated by greenhouse gases, buying humankind precious time against the worsening effects of climate change.
Deep-water bodies retain the ability to remove excess carbon rapidly from the atmosphere. They also transport the carbon into depths where it mixes and binds with minerals. As on land, marine carbon capture strategies fall into two categories.
(i) Biotic approaches take advantage of living systems like mangroves and macroalgae or of our rivers to carefully calibrate biomass burial at sea.
(ii) Abiotic approaches manipulate physical or chemical properties, such as through ocean alkalinity enhancement (OAE), and are more complicated but are also becoming unavoidable.
Both these methods promise to capture and store carbon for the long term and potentially transform countries’ contributions to climate goals.
Biotic, or nature-based, solutions rely on the inherent potential of ecosystems to sequester carbon while supporting biodiversity conservation and coastal protection.
●They are also relatively well-established, with some already integrated into national climate plans.
●However, their carbon sequestration potential is modest — typically capped at less than one billion tonnes of carbon dioxide every year — and storage durations are limited to hundreds or at best thousands of years.
Abiotic techniques, by contrast, offer greater scalability and permanence. For example, biomass burial at sea, if done right, can sequester seven to 22 billion tonnes of carbon dioxide per year.
●Reducing the acidic nature of the seas through OAE is another option. Here, alkaline materials are added to sea water to neutralise its carbon dioxide content, locking the carbon away for tens of thousands of years in the form of dissolved inorganic molecules.
●This method could potentially sequester one to 15 billion tonnes of carbon dioxide per year, an order of magnitude higher than biotic methods.
Challenges
●Techniques like ocean iron fertilisation, which claims to stimulate phytoplankton blooms to capture carbon dioxide, can disrupt other ecosystems and lower the oxygen content of deeper waters.
●Macroalgae cultivation, another proposed solution, carries similar risks when decaying biomass alters the local chemistry.
●Even OAE, which experts have touted for its scalability, raises concern about its consequences for marine biodiversity and the energy-intensive processes it may require.
●Public perception further complicates deployment.
●Measuring how much carbon is captured and stays buried also remains a challenge since the seas are expensive to monitor.
●Many people view abiotic techniques as unnatural or harmful and favour biotic approaches instead, like direct air capture.
Way forward
●Overcoming this scepticism will require communication, rigorous assessments, and stakeholder engagement. Critically, mCDR is not a substitute for reducing emissions. It cannot offset the current scale of fossil fuel combustion.
●However, as the world transitions toward net-zero emissions, leveraging the oceans and the seas becomes indispensable.
●The careful study of geological and ecological methods offers a chance to harness their power and vastness of oceans.
●Success hinges on rigorous science, robust governance, and societal trust.
●The Indian Ocean, with its vast arms holds untapped promise for deep carbon burial, potentially capturing 25-40% of the marine carbon dioxide.
●Harnessing these natural systems could provide a critical edge, turning the tide on runaway warming.
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