IELTS Reading 197: The Forest That Breathes the Tide — Mangroves and Their Hidden Worth

Adapted from UNEP / IUCN / Frontiers in Marine Science (2021–2026). IELTS Reading Section 3 difficulty, approximately 1,050 words. Source: http://www.unep.org/news-and-stories/story/mangroves-are-making-comeback-heres-whats-working

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Reading Passage

A. Where land meets sea in the tropics grows a forest unlike any other. Its trees stand in waterlogged mud that shifts twice a day with the tide, their tangled roots arching above the surface like the legs of great wading animals, breathing air through pores that would drown in the anoxic silt below. To a casual eye the place looks like a tangle of wood and mud, yet every part of it is an adaptation to a habitat that few plants can tolerate, from the salt-excluding leaves to the seeds that drift on the tide. Mangroves are not one species but a score of unrelated trees that have independently solved the same problem: how to live where neither land nor sea quite prevails. For decades these swamps were seen as worthless wastelands to be drained for shrimp ponds, timber or coastal development, and in many regions they were cleared faster than almost any other ecosystem. That view has reversed almost completely. Ecologists now describe mangroves as among the most valuable ecosystems on Earth, and the reason lies less in the trees themselves than in everything the forest does for free — services that a human engineer would have to build at enormous cost to replace.

B. The service most obvious to the people who live beside them is protection. A dense wall of roots dissipates the energy of incoming waves before they reach the shore, and researchers estimate that healthy mangrove belts can cut wave heights by roughly a third. In doing so they blunt storm surges, slow the erosion of the coastline and buy time against the slow rise of the sea. Villages built on stilts above such forests — as on the Pacific coast of Colombia, where a single estuary supports more than a hundred bird species — rely on them as a living breakwater that no concrete barrier can fully replace, and one that keeps growing rather than crumbling. When a cyclone strikes, the difference between a mangrove-shielded shoreline and an exposed one is measured in homes and in lives. Coastal engineering has, in recent years, begun to copy rather than compete with this effect, planting belts of trees instead of piling concrete. The trees are nurseries too: their tangled roots shelter young fish and crustaceans that later move out to sea, underwriting the coastal fisheries that feed millions who never see the forest itself. A single hectare of healthy mangrove can support far more juvenile marine life than the bare mudflats left behind after it is cleared.

C. Beneath the water lies a service whose value became clear only recently. Mangroves are powerful "blue carbon" ecosystems, alongside salt marshes and seagrass meadows. Because the mud in which they grow is starved of oxygen, the leaves and roots that fall into it decompose extremely slowly, locking carbon away in the sediment for centuries rather than releasing it back to the air. That mud also traps silt and pollutants carried down from the land, cleaning coastal water as it passes. Measurements of intact forests have found total ecosystem stocks approaching 700 tonnes of carbon per hectare — a density that, per unit area, exceeds many tropical rain forests. Destroy a mangrove, and not only do you lose that storage capacity but centuries of buried carbon can oxidise and return to the atmosphere, turning a carbon sink into a source. This is why mangrove protection has become a serious strand of climate policy rather than a marginal conservation cause, and why investors now count these forests among the cheapest options for offsetting emissions.

D. Yet the headline story of the past decade is unexpectedly encouraging. By tracking satellite imagery of mangrove extent from the 1980s to 2023, researchers found that the rate at which the world was losing these forests has slowed sharply, while the area coming back has grown. Natural regeneration — new seedlings colonising abandoned ponds and softening shorelines — is now offsetting much of the historical decline. The implication is that mangroves are more resilient than the pessimistic accounts of recent decades assumed: give a shoreline a chance and the forest can return without intensive planting, provided the water and sediment conditions still suit it. This is a rare piece of good news in the wetland record, and it has quietly shifted the emphasis from rescue to retention — from heroic replanting to simply leaving remaining forests standing. It also warns against complacency, because the same satellite record shows that clearance for aquaculture and coastal development has by no means ended everywhere.

E. The catch is that not every restoration project succeeds. Too often, schemes are guided by expert intuition rather than quantitative understanding, and they have a high failure rate, while judging whether a restored forest is truly recovering may take decades because mangroves grow slowly and carbon stocks build gradually over a generation. The commonest mistake is planting a single species thickly on an exposed shore where the water and sediment no longer suit it, only to watch the trees die back within a few years. Modellers are now building simulations of how different species, water flows and sediment conditions interact, aiming to plant the right tree in the right place rather than the cheapest tree anywhere, and to predict whether a site will gain or lose carbon as it matures. Mangroves illustrate a larger truth: the cheapest coastal defence and the most efficient carbon capture are not engineered but grown. The challenge is no longer proving that the forest works — it is learning, humbly and at scale, how to let it. The knowledge is still slowly accumulating, but the direction is now unmistakably and firmly clear to everyone who studies these coasts.

Questions 1-4

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

List of Headings i. A living breakwater and fish nursery ii. How mangroves got their name iii. Carbon locked in oxygen-starved mud iv. An unexpected recovery in satellite data v. Why planting the wrong tree fails vi. The decline of coastal fisheries vii. Engineering versus nature

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 problem have mangroves evolved to solve? A. Surviving on dry desert sand. B. Living on the land-sea interface in waterlogged, tidal mud. C. Growing in fresh mountain streams. D. Resisting fire in tropical forests.

6. By roughly how much can a healthy mangrove belt reduce incoming wave heights? A. By about one third. B. By almost 90 per cent. C. Wave heights are unaffected. D. It doubles wave heights.

7. Why do mangroves store so much carbon? A. Their trees grow unusually fast. B. Oxygen-starved mud slows decomposition of fallen material. C. They absorb carbon from the air directly through leaves. D. They are regularly burned.

8. What did the long satellite record reveal? A. Mangrove loss has accelerated every decade. B. Natural regeneration is now offsetting much of the decline. C. Mangroves have disappeared entirely from the tropics. D. Restoration has always had a near-perfect success rate.

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. A healthy mangrove ecosystem can store carbon at densities exceeding many rain forests.
10. Destroying a mangrove can turn a carbon sink into a carbon source.
11. The rate of global mangrove loss has increased since the 1980s.
12. Mangroves always recover successfully after planting.
13. Mangrove wood is the most profitable timber in the tropics.

Questions 14-15

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

Mangroves are valued as (14) __________ carbon ecosystems, because the oxygen-poor mud slows decomposition and locks carbon into the (15) __________ for centuries.

Answers & Explanations

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