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Role of Rivers Oceans in the Fight Against Climate Change
Context:
The ocean, often referred to as the Earth’s vast blue lung, plays a pivotal but frequently overlooked role in regulating the planet’s climate.
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- It absorbs approximately 25% of anthropogenic carbon dioxide emissions and over 90% of the excess heat generated by greenhouse gases, buying humanity valuable time to address the escalating climate crisis.
- However, this remarkable capacity to buffer climate impacts comes at a cost.
- The consequences of ocean acidification, disrupted biogeochemical cycles, pollution, and damage to marine ecosystems are becoming increasingly evident.
- Acidification endangers calcifying organisms such as corals and shellfish, while warming disrupts ocean circulation and depletes oxygen in critical habitats.
- These changes ripple through ecosystems, threatening fisheries, carbon sequestration, and other essential services.
Exploring Marine Carbon Dioxide Removal
- As the urgency to reduce carbon emissions and enhance climate resilience grows, marine carbon dioxide removal (mCDR) is emerging as a complementary strategy to emissions reduction.
- Unlike terrestrial solutions, which have dominated climate interventions so far, oceans, seas, rivers, and lakes offer a unique suite of options for carbon removal.
- Studies suggest that land-based carbon capture systems are nearing saturation due to soil and rock degradation, limiting their efficacy.
- Deep water bodies, on the other hand, possess the ability to remove excess carbon swiftly from the atmosphere and transport it to depths where it binds with minerals.
- Marine carbon capture strategies fall into two categories:
- Biotic Approaches: These leverage living systems such as mangroves, macroalgae, or river ecosystems to sequester carbon through biomass burial at sea.
- Abiotic Approaches: These involve manipulating physical or chemical properties, such as through ocean alkalinity enhancement (OAE), which chemically neutralises carbon dioxide in seawater.
Comparing Biotic and Abiotic Methods
- Biotic methods, or nature-based solutions, capitalise on ecosystems’ inherent ability to sequester carbon while supporting biodiversity and coastal protection.
- These solutions are well-established and integrated into some national climate strategies.
- However, their carbon capture potential is modest, typically under one billion tonnes of carbon dioxide annually, with storage durations limited to hundreds or thousands of years.
- Abiotic techniques, by contrast, offer scalability and longer-term storage.
- For example, carefully managed biomass burial at sea could sequester 7–22 billion tonnes of carbon dioxide annually, while OAE could lock away 1–15 billion tonnes per year for tens of thousands of years.
- These figures far surpass the potential of biotic methods.
- For example, carefully managed biomass burial at sea could sequester 7–22 billion tonnes of carbon dioxide annually, while OAE could lock away 1–15 billion tonnes per year for tens of thousands of years.
Challenges and Risks
- Techniques like ocean iron fertilisation, which promotes phytoplankton blooms to capture carbon, may disrupt ecosystems and deplete oxygen in deeper waters.
- Similarly, macroalgae cultivation can alter local chemistry when decaying biomass accumulates.
- Even the scalable OAE method raises concerns about its impact on marine biodiversity and the energy-intensive processes it entails.
- Public perception further complicates the adoption of abiotic methods.
- Many view these techniques as artificial or potentially harmful, favoring biotic or land-based solutions like direct air capture.
- Moreover, measuring and verifying the effectiveness of carbon capture in vast, turbulent oceans remains a logistical and financial challenge.
The Role of Oceans in Climate Solutions
- Importantly, mCDR is not a substitute for reducing emissions.
- The current scale of fossil fuel combustion—over 40 billion tonnes of carbon dioxide annually—cannot be offset solely by these methods.
- Instead, mCDR can complement emissions reductions as the world transitions to net-zero.
- India, with its vast coastline and the expansive Arabian Sea and Bay of Bengal, holds immense potential for leveraging oceans in carbon removal.
- The Indian Ocean alone could potentially capture 25–40% of global marine carbon dioxide.
- However, India has yet to fully explore the transformative opportunities its seas and rivers offer in combating climate change.
Harnessing the power of oceans and other water bodies could provide a critical edge in mitigating climate change. However, the success of marine interventions hinges on rigorous scientific research, robust governance frameworks, and societal trust.
