IELTS Reading 177: The Meadows the Sea Forgets

Adapted from the European Commission Environment / Nature Communications (August 2026). IELTS Reading Section 3 difficulty, approximately 1,050 words. Source: https://environment.ec.europa.eu/news/conserving-seagrass-meadows-crucial-blue-carbon-climate-strategies-2026-08-19_en

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Reading Passage

A. Forests have long been the public face of carbon removal. When governments and companies look for ways to offset emissions, they reach instinctively for trees: plant a million saplings, announce the scheme at a conference, count the carbon absorbed over the following decades. Less familiar is the fact that some of the most efficient carbon-storing ecosystems on Earth grow not on land but under water, and they are not trees at all. Seagrasses are flowering plants — the only flowering plants that have returned to the sea — which form meadows across shallow coastal sediments from the tropics to the Arctic. They cover barely 0.2 percent of the ocean floor, yet they account for more than 10 percent of the organic carbon buried in marine sediments every year. Pound for pound, hectare for hectare, they pack away carbon faster than almost any terrestrial forest, and they keep it for centuries or millennia in sediments where oxygen is too scarce for microbes to rot it away. The comparison is not flattering to forest carbon: a woodland must wait decades for a tree to grow, and much of its stored carbon returns to the air when the tree dies. A seagrass meadow, by contrast, buries carbon in mud that outlasts the plants themselves by thousands of years.

B. A 2026 global synthesis, welcomed by the European Commission as a landmark for "blue carbon" accounting, has now put numbers on this long-recognised but poorly quantified asset. Researchers compiled measurements from thousands of sampling sites, assigned them to global seagrass bioregions, and compared the above- and below-ground biomass and net primary production across the dozen or so seagrass genera. Their estimate: between 24 and 40 megatonnes of carbon stored in living seagrass biomass worldwide, spread across 160,000 to 266,000 square kilometres of meadow. Each year, the same meadows fix a further 83 to 137 megatonnes of carbon through photosynthesis. The range is wide, and that is itself a finding: seagrass carbon storage varies so much by region, species and depth that a single global average is nearly meaningless. Tropical turtle-grass beds store more per hectare than temperate eelgrass meadows; shallow, sunlit beds outperform deep ones; and the sediments beneath the plants — where roots bind mud and slow the water — hold far more carbon than the leaves above.

C. Why does seagrass bury carbon so effectively? The mechanism is biological and physical at once. The plants grow in dense meadows whose long blades slow the flow of tidal water, causing suspended particles to settle. Leaf litter and dead roots build up anoxic mud layers that persist for hundreds, in some places thousands, of years. Unlike leaves falling on a forest floor, where fungi and bacteria quickly consume most of the material and release CO2 back to the air, seagrass sediment is so depleted of oxygen that decomposition grinds almost to a halt. Recent work has also shown that seagrass beds export a portion of their organic carbon to adjacent ecosystems — roughly a quarter of their net production is washed out to sea or into mangroves and salt marshes — so their benefit extends beyond the meadow itself. The 2025 research on soil decay rates confirmed this: even over the last century, the organic carbon in seagrass sediments decays more slowly than in most terrestrial soils, at a rate of only a few percent per decade.

D. The trouble is that the meadows are vanishing. Coastal development, dredging, agricultural run-off that clouds the water with sediment and fertiliser, and the direct destruction of seabed by trawling have shrunk known seagrass extent by an estimated third over the past century, with losses accelerating in many regions. When a meadow dies, the carbon it stored for millennia is not simply left in place. The exposed sediment is stirred by tides and storms, microbes return, and decades to centuries of buried organic matter are oxidised back to CO2 and dissolved inorganic carbon within a few years. The world's largest seagrass meadow, in Shark Bay, Australia, has been modelled explicitly: a business-as-usual loss scenario would lock in around 90 megatonnes of future CO2 release by 2120, whereas a concerted restoration programme could turn that into a sink of more than 700 megatonnes over the same period — an eight-fold difference that depends almost entirely on whether humans choose to protect what remains.

E. This is why blue carbon has moved from a research curiosity into climate policy. If seagrass, mangrove and salt-marsh restoration can be reliably measured and verified, they can be written into national climate plans, traded as offsets, and used to justify the protection of coastal waters that were previously valued mainly for fishing. There are cautions. Recent work in the South China Sea has shown that seagrass beds also produce carbonate minerals through calcification, a process that can release CO2 back to the water and partly offset the organic carbon stored. The net benefit is still strongly positive, but it is smaller than early optimistic estimates suggested, and it varies from place to place. Microplastics, too, have been found accumulating in the same sediments that store the carbon, a reminder that the meadows are not isolated from human waste. The message is not that seagrass is a magic solution; it is that a hectare of healthy seagrass is worth protecting far more than a hectare of newly planted terrestrial forest, and that losing it is not a neutral act — it is a slow, deliberate release of the carbon that coastal ecosystems have sequestered since before agriculture began. As the measurement science improves, the choice is becoming less whether to value the meadows and more how quickly coastal planners can be persuaded to do so.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. Why seagrass buries carbon so efficiently ii. The surprising scale of seagrass carbon storage — and its wide variation iii. The value of blue carbon for climate policy, with cautions iv. The biology of flowering plants on land v. What happens when meadows die and the cost of inaction vi. The history of underwater diving vii. How mangroves outperform seagrass

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. What proportion of the ocean floor do seagrasses cover, and what proportion of marine carbon burial do they contribute? A. About 2 percent and 1 percent. B. About 0.2 percent and over 10 percent. C. About 10 percent and 0.2 percent. D. About 50 percent and 50 percent.

6. What did the 2026 global synthesis estimate for seagrass biomass carbon storage? A. 24 to 40 megatonnes. B. 700 megatonnes. C. 90 megatonnes. D. 83 to 137 tonnes.

7. Why does seagrass sediment preserve carbon for so long? A. The sediment is frozen year-round. B. Oxygen depletion slows microbial decomposition almost to a halt. C. Microbes cannot tolerate salt water. D. The plants actively pump the carbon into rocks.

8. What did the Shark Bay modelling compare? A. Two fishing quotas. B. A business-as-usual loss scenario versus a restoration programme by 2120. C. Two different seagrass species. D. The cost of two carbon-credit brokers.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. Seagrasses are the only flowering plants that have recolonised the sea.
10. The 2026 study found that a single global average accurately represents seagrass carbon storage.
11. Roughly a quarter of seagrass net production is exported to adjacent ecosystems.
12. Seagrass meadows have grown by about a third over the last century.
13. Seagrass restoration is more expensive than planting tropical rainforest.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

Seagrass meadows cover less than 0.2 percent of the ocean floor yet contribute over 10 percent of marine organic carbon burial. When a meadow dies, the exposed sediment is stirred by tides and storms, and buried organic matter is (14) __________ back to CO2. Recent research also warns that calcification in seagrass beds can partly (15) __________ the organic carbon stored.

Answers & Explanations

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